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How to find the molecular formula


how to find the molecular formula The molar mass of zinc phosphate is M=386. 0% C, 6. Divide the molar mass of the compound by the empirical formula mass. If correct case is not used, the formula may be ambiguous and the interpretation chosen may not be the desired one. Which of the following pure aluminium samples contains the largest number of atoms. 0 % carbon, 6. 01 1. 80% carbon, 20. 4) Calculate how much oxygen is needed to balance the charge by taking the sum of the apfu charges and dividing by ‐2 5) Calculate the O‐factor based on the idealized chemical formula 6) Multiply the O‐factor by the apfu values Once these steps are complete, an analysis based on the oxides can be Determining The Molecular Formula. formula HO. Apr 01, 2020 · How to Calculate the Unity Molecular Formula Glaze Calculation Online- Sample Lecture Using the CMW glaze calculator for Excel Determining The Molecular Formula. 49. 3% O. Worksheet: Calculating Empirical & Molecular Formulas 1. molecular mass 78. Calculate the molecular formula given the measured mass is 27. Calculate the molecular formula of a compound with molecular weight 107. The molecular formula is C 4 H 10 (the maximum number of bonded hydrogens by the 2n + 2 rule). 0) + (2 nitrogen x 14. Please help me out here. The formula is therefore Ca 3 (PO 4) 2. , C6H6). As we know 2 is the common factor of 8, 10, 4 and 2. Example- Molecular Formulas (Steps 5-7) It has a molar mass of 194. 3. The next step is to weigh a sample, then divide the empirical mass into the actual mass of the compound. STEP 2: Divide the given molecular molar mass by the molar mass calculated for the empirical formula. Formulas like C6H6 or C3H5NO2 tell anyone who reads how many of each atom is contained in a molecule. Jul 27, 2017 · That means the empirical formula of this compound is CH 5 N; Steps for Finding The Molecular Formula from Empirical Formula. The Molecular Formula 24 Fructose is found to contain 40. empirical formula is C4H5N2O. com View All . Click again to see term 👆. Use correct case for element symbols. So if 1 mole has a mass of 106g 1 formula unit would have a mass of 106g/6. 6 g. This should give you a whole number Sep 20, 2021 · Any compound’s chemical formula can be defined using one of two types of formulas: molecular formulas and empirical formulas. The molecular formula is related to the empirical formula, and represents the actual number of atoms of each type in a compound. Determine the EF and molecular formula. 1 A compound is found to contain 85. 4: Nitrogen. In another experiment its molar mass is found to be 56. 98\%$ nitrogen and has a molecular mass of $160. The molecular weight of this compound is 180 g/mol. 04 mol Next, simplify the ratio of the molecular mass: empirical mass. ) Its molecular weight, however, is 34, not 17 Daltons. The obtained spectrum showing a base peak with its mass (with 4 decimals) and molecular formula and there is no information about the calculated mass of compound. empirical formula. Find its molecular formula. 7. 66. The molecular formula does NOT tell us how the atoms are arranged within the molecule. As the name suggests, an empirical formula mass is the sum of the average atomic masses of all the atoms represented in an empirical formula. Procedure Chemical formulae and equations Derivation of formulae (key points) Chemical Formula Definition: An expression which states the number and type of atoms present in a molecule of a substance. In the 13 eV EI spectrum, less fragmentation is observed because the ionization energy is much lower. Next, divide the molecular weight by the empirical formula weights to come up with a ratio. Finally, combine the two ions to form an electrically neutral compound. Multiply all the subscripts in the empirical formula by the whole number found in step 2 ; Example: Lets consider water which has a molar mass of 18g/mol and its empirical formula molar mass is H 2 O. It has a molecular weight of 318. 01 13. Then multiply that number by the EF to get the MF. . Tap card to see definition 👆. 9 hours ago Differencebetween. ü Determine the number of moles and . Procedure Empirical Formula Calculation with Related … 6 hours ago Byjus. To get the molecular formula, you must divide the molar mass of the empirical formula into the given molecular formula mass to find the multiplier. Divide the molar mass of the compound by the molar mass of the empirical formula. Similarly one may ask, how can a molecular formula be obtained from an empirical formula? Empirical formula weight = (1×12 g/mol)+(2×1 g/mol)+(1×16 g/mol) =30 g/mol. Then, we have to divide the molar mass for the molecular formula by the empirical formula mass. Molecular formulas are derived by comparing the compound’s molecular or molar mass to its empirical formula mass. 9. Step 7: Obtain molecular mass ( or molar mass) either from experiment or from the vapour density of the compound by using the relationship. Find the molecular formula of A. Now calculate the ratios of the moles. *Sorry for the gap in the video, I had to quickly make room to record more footage. To calculate Molecular Formula, you need Molar Mass (M) and Mass of Empirical Formulas (EFM) . Molar mass of CH 2 O = (1 x 12) + (2 x 1) + (1 x 16) = 12 + 2 + 16. Determine the number of moles by dividing the grams by the atomic mass. formula of sodium sulfate is Na 2 SO 4. Step 1: First, calculate the empirical mass for CH g 12. 37% H by mass. After calculating the moles of gas, you need to Calculate the molecular weight of the gas. all of which could be on this first quiz. Calculate the empirical formula mass (EFM), which is simply the molar mass represented by the empirical formula. 0) + (5 hydrogen x1. It is the empirical formula, multiplied by a whole number. Here, n is the number of moles, P is the pressure, V is the volume, T is the temperature in Kelvin, and R is the gas constant. Next moles have to be calculated by converting these masses. Empirical formulas show the simplest whole-number ratio of atoms in a compound, molecular formulas show the number of each type of atom in a molecule, and structural formulas show how the atoms in a molecule are bonded to each other. Example 1: To find the empirical formula of a sulfide of copper, 1. Divide the molar mass of the compound by the empirical formula molar mass. Mass per hundred gram sample is used for this purpose. 01g/mol) Dividing its molar mass (34. To . 0 g C x 1 mol C = 3. Jun 28, 2021 · In order to go from the empirical formula to the molecular formula, follow these steps: 1. Multiply the molecular weight of the substance by the number of moles you wish to have, which in this case is 1. 178$. 33 mol C Sep 27, 2008 · 3) Just multiply replace x,y and n and you will get the actual formula. 250 mg nicotine combusted to form 14. The effectiveness of the SO 2 to protect the wine from oxidation and microbial spoilage is dependant upon the pH of the wine. Molecular mass of the compound = 18 g/mol 18 g / m o l. The 34-Dalton formula mass corresponds to the molecular formula H 2 O 2. The molecular formula is the formula that specifies the actual number of atoms present in the compound. Then, we should find out how much CH 2 O units are present there. 9/24/14 2 ü Calculate the molar mass of a molecule from its chemical formula and a table of atomic masses and how to convert the mass of a molecular substance to moles, number of particles, or volume of gas at standard temperature and pressure. Sep 03, 2019 · Divide the molar mass of the compound by the empirical formula mass. Empirical Formula Calculation with Related … 6 hours ago Byjus. 5% x 195 / 12 = 8. the molecular mass of this unknown compound is 180 amu. As an example, a particular compound is 80% C and 20% H. The terms formula weight and molecular weight are often used interchangeably, but formula weight includes simple or empirical formulas of compounds, as well as, molecular formulas. 956 g of copper wire is heated Any of the above searches can be run on their own or in combination with any others. If the four carbon atoms form a ring, two hydrogens must be lost. The basic steps for formula calculation are: Divide the weight percentage of each oxide by the formula weight of that oxide. Multiply the subscripts in the empirical formula by this number to determine the molecular formula. . Basically, the mass of the empirical formula can be computed by dividing the molar mass of the compound by it. With our tool, you need to enter the respective value for Molar Mass . Calculating Molecular SO 2 Molecular SO 2 is calculated using the free SO 2 of a wine and a molecular SO 2 factor related to the pH of the wine. Dec 16, 2017 · How to Find The Atomic Mass, Molecular Mass, Empirical Formula & Molecular Formula (Stoichiometry) by Flex: 12:00 am On December 16, 2017 Stoichiometry is the calculation of mass / volume relationships of a chemical reaction. Balancing Charges. What is the molecular formula for this compound? Strategy: Find the empirical formula. To find the ratio between the molecular formula and the empirical formula. Molecular Ion. 7% H, 53. Just use a periodic table to find the mass of K and Cl, thus finding the mass of 1 mole of KCl, then just divide the mass given in the question: 1 mole = (35. 0g/mol. 6% C and 14. Step 5 After you determine the empirical formula, determine its mass. A common organic solvent has an empirical formula of CH and a molecular mass of 78 g/mole. The average molecular mass of a chloroform molecule is therefore equal to the sum of the average atomic masses of these atoms. 99\%$ carbon, $5. 31 g/mol. The molecular formula of chloroform indicates that a single molecule contains one carbon atom, one hydrogen atom, and three chlorine atoms. Use the molecular formula to find the molar mass; to obtain the number of moles, divide the mass of compound by the molar mass of the compound expressed in grams. g. The atomic weights are: C (12. 43% hydrogen, and 20. For example, while the molecular formula for glucose is C 6 H 12 O 6, its empirical formula is CH 2 O – showing that there are twice as many hydrogen atoms as carbon or oxygen atoms, but not the actual numbers of atoms in a single molecule or how they are arranged. To do that you need to know how many grams of gas was present in the molecule. Created by Sal Khan. Here‘s an example: What is the molecular formula of a compound . Search by Tags To get the molecular formula, you must divide the molar mass of the empirical formula into the given molecular formula mass to find the multiplier. Then, add together the atomic weight of each of the atoms in the formula, which you can find using the periodic table. 10: Hydrogen. Search by Tags Sep 14, 2021 · Find the molecular weight of the substance you’d like to make a molar solution of in g/mol. ü Interconvert grams, moles, and numbers of formula units. 7 g / m o l 13. 67 mol C 20 g H / 1 g/mol = 20 mo. Then, identify the anion and write down its symbol and charge. These compounds all have the same empirical formula but different molecular formulas. What is its molecular formula? Molecular Formula: Example Molecular Formula Input Molecular Formula (MF) -- Specification of the count of each element in a compound. 008) = 14. Multiply all the subscripts in the empirical formula by the whole number found in step 2. Step 1: Write the molecular formula for the molecule: X a Y b: a and b are both numbers May 13, 2019 · A molecule with a molecular weight of Finding the empirical and molecular formula is basically the reverse process used to calculate mass percent or mass percentage. Assume that you have 100 g of the compound. •In some cases the molecular formula is a whole-number multiple of the empirical formula. In chemistry, the empirical formula of a chemical compound is the simplest positive integer ratio of atoms present in a compound. 71 g H 53. No ads = no money for us = no free stuff for you! Using a Molecular Formula to Determine Which Elements are Present in a Molecule. 1 g/mol. Calculate the empirical formula of the compound from the grams of carbon, hydrogen, and oxygen. Divide the gram molecular mass by the empirical formula mass. For example, the molecular formula for water is H 2 O. Molecular Formula Determination Method 1 • Obtain the empirical formula • Compute the mass corresponding to the empirical formula. Step 5: write down the empirical formula of the compound. Calculating Molecular Formula (You are given the molecular mass for questions like this) Work out the mass of the empirical formula. To find the formula of an ionic compound, first identify the cation and write down its symbol and charge. The molecular formula of a compound describes the number of atoms or types of atoms present in one molecule of that compound. After what I have done last, there are only a few more steps to find the empirical formula and then the molecular formula itself, but I think what I have done is . In order to find out molecular formula of a compound, the first step is to determine its empirical formula from the percentage composition. =6 empirical mass 13. Molecular mass = 2× Vapor . To be able to find the molecular formula, you’ll need to given the molar mass of the compound. We use that. = 30. The empirical formula of a compound may be defined as the formula which gives the simplest whole number ratio of atoms of the various elements present in the molecule of the compound. 19 g/mol. What is its percent composition? Solution To calculate the percent composition, the masses of C, H, and O in a known mass of C 9 H 8 O 4 are needed. For example, the molecular formula of butene, C 4 H 8, shows that each freely existing molecule of butene contains four atoms of carbon and eight atoms of hydrogen. Empirical formula weight = (1×12 g/mol)+(2×1 g/mol)+(1×16 g/mol) =30 g/mol. What is the molecular formula for hydral. For this, we follow the same procedure that we did for examples 1 and 2. STEP 1: Calculate the molar mass of the empirical formula. Step 6: Calculate the empirical formula mass by adding the atomic masses of all atoms present in the empirical formula. It has a molar mass of 160 g. For now, forget the number of grams of the compound. There are two atoms of hydrogen and one atom . Step 6 Determine how many times greater . (4 carbon x 12. 02 x 10^23 is the number of formula units in 1 mole. The best you can do is to find an empirical formula. The molecular formula is the blueprint of a molecule. Jun 28, 2021 · Empirical formulas can be determined from the percent composition of a compound. Mar 02, 2019 · If the relative molecular mass of "A" is 123. The subscripts in the formula are first used to calculate the mass of each element found in one mole of the compound. value later. Mar 30, 2020 · For example: The molecular formula for glucose is C 6 H 12 O 6. 63% C and 14. This is because positive and negative charges attract each other. 02 x 10^23 where 6. In the 70 eV EI spectrum, the highest m/z ion appears to be m/z 154. Determine the masses of each component in the compound. Jun 15, 2020 · The molecular formula of a compound may be the empirical formula, or it may be a multiple of the empirical formula. If we divide this by 6, we get C 1 H 2 O 1. The empirical formula for the compound having the formula H2C2O4 is [A] C2H2 [B] CO2H [C] COH [D] C2O4H2 [E] COH2 2. There are three main types of chemical formulas: empirical, molecular and structural. Search by Tags empirical formula. Click card to see definition 👆. • Using the empirical formula to obtain the molecular formula. Jul 17, 2013 · You would simply find the mass of the empirical formula (if your formula was CH2, you would find the atomic mass of C and add it to the atomic mass of H, which is multiplied by 2 to account for the 2 H’s in the formula). This means you can search by substructure and molecular formula, or melting point and molecular weight, giving you powerful options for finding the information you are looking for or identifying unknown compounds. 01 g/mol = 2 The formula to calculate that is n = PV/RT. 74% hydrogen, and 18. We indirectly calculated the mass of the water and then used these values to derive the molecular formula. The general MF query syntax consists of a series of valid atomic symbols (please consult your periodical chart), each optionally followed by either a number or a range. Determining Percent Composition from a Molecular Formula Aspirin is a compound with the molecular formula C 9 H 8 O 4. Sep 30, 2019 · The simplest type of formula – called the empirical formula – shows just the ratio of different atoms. The result is the molecular formula. 008), and O (16). chemical formula of the substance. In this video, we'll walk through this process for the ionic compound calcium bromide. The “2” outside the parentheses means we have two of the entire polyatomic ion PO 4 (a total of 2 phosphorus atoms and 4 oxygen atoms). Molecular Formula is the expression of the number of atoms of each element in one molecule of a compound is calculated using molecular_formula = Molar Mass / Mass of Empirical Formulas. Determining The Molecular Formula. Calculate the empirical formula of a compound that is 85. With these tools in hand, calculating the molecular formula involves three steps: Calculate the empirical formula mass. 44g H and 6. 3 Hence, the empirical formula of the compound is H2O H 2 O. molecule, the molecular formula is N3O6. II. 92g O. Chemists use an instrument called a mass spectrometer to determine the molar mass of compounds. 71 % hydrogen and the rest oxygen. Any of the above searches can be run on their own or in combination with any others. Difference Between Empirical and Molecular Formulas . (This formula only means the hydrogen peroxide molecule contains equal numbers of hydrogen and oxygen atoms. 2. 01 + (2 × 1. [/B] I have showed my attempt at solving this problem, but I think it is wrong. 10% oxygen by mass. The molecular formula, on the other hand, describes how the compound is put together. We accomplished this by massing the hydrate, boiling off the water and measuring the resulting anhydrous compound. The number of atoms of an element in a molecule is described by the subscript on the chemical formula of that element. 1) 74. 0) =97. 110 g/mol. 29 g O Convert the masses into moles of each element: 40. 0 mol carbon (2x amount in empirical calculations) molecular formula is C8H10N4O2. Empirical Formula= C 4 H 5 ON 2. We can then find the empirical formula mass by adding together the masses of its . Jun 15, 2011 · Incidentally, this is why different compounds can have the same empirical formula; while they contain different numbers of molecules in different arrangements, if the elements and their ratios are the same, the empirical formula will be the same as well). First we will use the molecular formula of sucrose (C 12 H 22 O 11) to calculate the mass percentage of the component elements; then we will show how mass percentages can be used to determine an empirical formula. Apr 08, 2018 · You need to find the empirical formula first to proceed. and you found Benzene :) The second part is as simple. molar mass EFM = 27. The molar mass of fructose is 180. STEP 3: Multiply each subscript by the whole number that resulted from step 2. To calculate Molecular Formula, you need Molar Mass (M) and Mass of Empirical Formulas (EFM). 84 g / m o l = 2. The empirical formula is C4H5N2O. In the previous section, we discussed the relationship between the bulk mass of a substance and the number of atoms or molecules it contains moles. In order to determine its molecular formula, it is necessary to also know the molar mass of the compound. Jun 13, 2011 · The molar mass would be 23x2 + 12x1 + 16x3 = 106g/mole. 47 g/mol. Aug 23, 2021 · Retrieval of standard chemical formulas for minerals from chemical analyses is an exercise in (a) conversion of units of quantity and (b) normalization of sums to match the commonly used formula conventions. That means you have 80 g C and 20 g H 80 g C / 12 g/mol = 6. To determine the empirical formula of a known substance, such as glucose, we take the subscripts of the molecular formula (C 6 H 12 O 6) and reduce then to the simplest whole number ratios. In 5 g there would be 5/106 moles present. Calculate the molecular formula for this compound and name it. Now we will find the molecular formula as follows: Molar mass of empirical . It goes through a combustion reaction, finding the molecular formula, and balancing a complicated equation. Find empirical/molecular formula for nicotine (contains carbon, hydrogen, nitrogen) if 5. The result determines how many times to multiply the subscripts in the empirical formula to get the molecular formula. Use formula Molecular Mass = n x Empirical Mass to find out the value of n. 1. I have found in literature, where . Calculate the molecular formula of a compound whose molecular weight is 300 g/mol, and has the following components: 60. A molecular weight of a substance is the sum of all the atomic weights of all the atoms in a molecule of a molecular substance. Example 2: The empirical formula is BH3 of boron hydride. To complete this quiz, you must have a periodic table and a calculator. Formic acid. Chemical Formula Search Help Rules for chemical formulas (Back to search) Enter a sequence of element symbols followed by numbers to specify the amounts of desired elements (e. A sample with a molar mass of 34. 1 atom of sulfur = 1 x (32) = 32. Find the empirical formula mass of the compound. This quiz covers simple empirical and molecular formula calculations. May 19, 2017 · Finding the molecular formula of a compound. To find that whole number, just divide the molar mass of the compound by the empirical formula mass of the compound. (2) Please do not block ads on this website. What is empirical formula# how to find empirical formula# Class XI. When the empirical formula Determining the Molecular Formula from the Empirical Formula. 4% H (by ma To do this, we need to determine the empirical formula from the molecular formula. Divide Molar Mass by Empirical Mass to get the value of n. Hence, the molecular formula is C8H10N4O2. Similarly one may ask, how can a molecular formula be obtained from an empirical formula? Jul 17, 2013 · You would simply find the mass of the empirical formula (if your formula was CH2, you would find the atomic mass of C and add it to the atomic mass of H, which is multiplied by 2 to account for the 2 H’s in the formula). Its formula has twice as many oxygen atoms as the other two compounds (one each). May 22, 2018 · Brought to you by Sciencing. Round off the mole ratios to the nearest whole number. In order to determine its molecular formula, it is necessary to know the molar mass of the compound. The molecular formula for the same compound will equal to n × (CH 2), in other words, the molecular formula for this compound will be C n H 2n Using the periodic table of the elements we can determine the empirical formula mass of this compound(CH 2 ): 12. Sep 27, 2008 · 3) Just multiply replace x,y and n and you will get the actual formula. 4% H (by ma There are three main types of chemical formulas: empirical, molecular and structural. Formula to calculate molecular formula. 33 mol C Mar 02, 2019 · If the relative molecular mass of "A" is 123. 16 g/mol. 026 Apr 06, 2018 · To find our molecular formula, we need to find the molar mass of our empirical formula (4*12+5*1+2*14+16= 97 g/mol) The molar mass of the empirical formula will ALWAYS be less than the molecular formula unless the empirical formula is the molecular formula in which case they'd be equal. This can be done by adding the atomic mass of each of the elements present in the compound. 01 g/mol = 2 Molecular Formula: The actual formula for a molecule. Step 1: Write the molecular formula for the molecule: X a Y b: a and b are both numbers Sep 18, 2011 · The molecular formula of a compound can be found if you have the percent composition of each element on the compound and the molar mass. Take the molecular mass and divide by the result from the previous step. Dec 02, 2014 · Hydralazine is a drug used to treat heart disease. 083 mg H 2 O. For that, first, calculate the molar mass of empirical formula and then divide the given molar mass value from the calculated value. Therefore, the higher the pH a wine has, the less effective the SO 2. For example, ethyl alcohol has the MF C 2 H 6 O. Formula to calculate empirical formula. The molecular formula indicates the exact number of atoms in the molecule. The empirical formula expresses the smallest whole number ratio of the atoms in the element. mass. 026 formula HO. Chemical formulas such as HClO4 can be divided into empirical formula, molecular formula, and structural formula. Determine the molecular formula of the compound with an empirical formula of CH and a molar mass of 78. Apr 15, 2020 · The percent composition of a compound can also be determined from its chemical formula. 02 g/mol) by the empirical formula mass gives the whole-number multiple: The molecular formula is H 2 . 2: Oxygen. 242 mg CO 2 and 4. Hence, the empirical formula of the compound is H2O H 2 O. Similarly, the introduction of a double bond entails the loss of two hydrogens, and a triple bond the loss of four hydrogens. 03\%$ hydrogen, and $34. What is its molecular formula? Molecular Formula: Example Mar 30, 2020 · For example: The molecular formula for glucose is C 6 H 12 O 6. mass by the mol. Problem: A compound is 75. 2 atoms of sodium = 2 x (23) = 46. Using mass spectrometry to determine the molecular ion allows us to identify possible molecular formulas. Chemical formulae and equations Derivation of formulae (key points) Chemical Formula Definition: An expression which states the number and type of atoms present in a molecule of a substance. Weigh out the number of grams you calculated in step 2 of your substance and place it in a container. 0) + (1 oxygen x 16. A . Determine the masses of each element assuming 100 g: 40. The key difference between empirical and molecular formulas is that an empirical formula only gives the simplest ratio of atoms whereas a molecular formula gives the exact number of each atom in a molecule. To calculate the molecular formula you need the ratio of . Multiply each of the subscripts within the empirical formula by the number calculated in Step 2. The result should be a whole number or very close to a whole number. Dividing the molecular mass through this value will be the following: Molecular formula mass / Empirical formula mass = 34 g/mol / 17. 3 Nov 29, 2014 · Finding the molecular formula is simple. The charges of the ions in a chemical formula always add up to zero. According to its molecular formula, each molecule of sucrose contains 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms. • Calculate the ratio Molar Mass/Empirical formula mass • The integer from the previous step represents the number of empirical formula in one molecule. This is now the molecular formula. 46% carbon, 4. You can find the empirical formula of a compound from its mass percent composition. Oct 20, 2020 · To find a molecular formula, start by calculating the number of moles and the molecular weight of the gas using their respective formulas. Hydrogen peroxide has the empirical formula HO (17. 00 g/mol is found to consist of 0. Determining the molecular formula is an important step to understanding any substance. Jun 13, 2020 · The second step of how to find molecular formula is to divide the gram molecular mass by the empirical formula mass. May 13, 2019 · A molecule with a molecular weight of Finding the empirical and molecular formula is basically the reverse process used to calculate mass percent or mass percentage. Sep 18, 2011 · The molecular formula of a compound can be found if you have the percent composition of each element on the compound and the molar mass. A structural formula shows the number of each type of atom, and the bonds between them. 01), H (1. 5 + 39. We will use the following example to help explain: A unknown organic compound is composed of 40. Apr 06, 2018 · To find our molecular formula, we need to find the molar mass of our empirical formula (4*12+5*1+2*14+16= 97 g/mol) The molar mass of the empirical formula will ALWAYS be less than the molecular formula unless the empirical formula is the molecular formula in which case they'd be equal. Feb 18, 2002 · The purpose of this lab was to find the amount of water and, thus, the molecular formula of an unknown hydrate. Calculate the mass percent. Jul 04, 2017 · The molar mass was given as 60 g/mol. 0 g C 6. Compare the empirical formula’s mass to that of the molecular formula by dividing the emp. 46% oxygen by weight. Both the empirical formula and the molecular formula represent the atom’s number and identity. For example, the molecular formula of hydrogen peroxide is H 2 O 2, as each molecule has two hydrogen atoms and two oxygen atoms. It is $59. Step 1 – calculate the molecular weight of the compound. This division produces a whole number. here : (C 1 H 1) 6 = C 6 H 6. how to find the molecular formula