Chemistry
Elements and Compounds

# How do you determine the molecular formula given the empirical formula?

###### Wiki User

Calculate the empirical formula weight. Find the ratio of the molecular weight to the empirical formula weight. (n= molecular weight/ empirical formular weight). Multiply each subscript of the empirical formula by n.

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## Related Questions

### What are the steps to determine molecular formula?

There are 4 step to determine molecular formula, which are given bellow Step:1:- Find empirical formula Step:2:- Find empirical formula mass Step:3:- Find n n=molecular mass/empirical formula mass Step:4:- now find molecular formula to find molecular formula molecular formula(empirical formula)n

### Explain why the percent composition of certain compounds are not sufficient to determine the compounds molecular formulas?

Because unlike the empirical formula, the molecular formula does not have to be the simplest ratio.If by chance you are given the percent composition of the elements in a substance, you could calculate the empirical formula and then the empirical formula's mass. However, the molecular formula equation is molecular formula= (empirical formula)n, where n is the mass of the molecular formula divided by the mass of the empirical formula. You would, therefore, need to know the mass belonging to the molecular formula, which you are not given.

### How does one determine a molecule formula from the empirical formula?

The density or some other information must be given that allow you to find the molar mass. Calculate the empirical formula mass. Divide molar mass by empirical formula mass. This answer is multiplied by all subscripts of the empirical formula to get the molecular formula.

### Determine the molecular formula of a compound if its empirical formula is C2H6O and its molar mass is 138g?

Because an empirical formula is the simplest form of a compound, we know that the molecular formula contains more atoms than it does. Since we are given the molar mass, we can use this formula. x ( MM of empirical formula ) = MM of molecular formula MM of empirical formula = 12(2) + 1(6) + 16 = 46 MM of molecular formula = 138 46x = 138 x= 138 / 46 x=3 Therefore, the molecular formula is 3(C2H6O) that is C6H18O3

### What is an empirical formula?

The chemical formula in which the subscripts are given in the smallest ratio.

### What are the steps in writing a molecular compound?

If you mean to find its molecular formula: 1. First you must obtain the empirical formula. Find the molar mass of the empirical formula. 2. The molar mass of the entire molecule must be given or its molecular formula cannot be find. 3. Put the molar mass given over the molar mass of the empirical formula. 4. Use this number (kind of like a scaler) to multiply by the entire empirical formula. This is the molecular formula.

### What is the empirical formula of butane C4H10?

The formula given for butane is a molecular formula. The empirical formula for any molecular is obtained by dividing all the element subscript numbers by the highest common factor of all the subscripts; in this particular instance leading to C2H5 as he empirical formula.

### What is the properly written empirical formula of a compound of molecular formula C6H12 with a molar mass equal to 84.16 gram per mol?

The information about the actual molar mass is superfluous. Given any molecular formula, the corresponding empirical may be obtained by dividing all the subscripts in the molecular by the largest integer that yield an integer quotient for each subscript. In the given formula, the empirical formula is CH2.

### How can you find the molecular formula of a compound when its percentage composition is given?

You have to find its empirical formula using the percentage composition. When you have done that, work out the relative molecular mass (Mr) of the empirical formula. This should be a multiple of the compound's Mr, so you multiply the amount of each atom in the empirical formula by this number, which gives you the final molecular formula.

### What is the molecular formula of a compound given that molar mass of the compound is 30.04 gram and the empirical formula is NH?

The molecular formula of this compound is N2H2. This is obvious because the empirical formula of a compound is the lowest positive integer ratio of atoms present.

### How does one determine a molecular formula from the empirical formula?

molar mass over grams of elementThe above answer is somewhat correct. In order to find the molecular formula when given the empirical formula, you must first find the molar mass of the empirical formula.MOLAR MASS# atoms element A x atomic mass element A (periodic table) = mass A# atoms element B x atomic mass element B (periodic table) = mass B... etc.Add up all of the mass values found above and you have the molar mass.Then, after you have found the empirical formula's molar mass, you divide the molar mass of the molecular formula by the empirical formula's molar mass (solving for n).MOLECULAR FORMULA EQUATION: N (Empirical formula) (read as N times empirical formula) where:N = Molar mass substance---- Molar Mass emp. form.

### A compound with the empirical formula SN was found in a subsequent experiment to have a molar mass of 184.32 gmol. What is the molecular formula of the compound?

The empirical formula of SN has a formula unit mass of the sum of the gram atomic masses of nitrogen and sulfur, i.e., about 46.0667. The gram molecular mass given in the problem divided by this formula unit mass is about 4. Therefore, the molecular formula is S4N4.

### How do you find the molecular formula?

In order to find a substance's molecular formula, proceed with the following steps. An element's molecular formula is either going to be equal to the empirical formula or is a multiple of the empirical formula (n).1. Find the empirical formula's molar mass. Calculate the molar mass of the empirical formula.# atoms element A x atomic mass element A = mass A# atoms element B x atomic mass element B = mass B... etc.Add up all of the mass values found above for the empirical formula's molar mass (MM).2. Solve this equation (below).n = MM compound (given) = Empirical Formula Units---- MM emp. form.3. After solving for n, multiply the empirical formula.Molecular Formula = N (Empirical Formula)Ex. What is the molecular formula of a compound which has an empirical formula of CH2 and a molar mass of 126.2g?1. Find the empirical formula's molar mass.1 atom carbon (C) x 12.01g = 12.01g2 atoms hydrogen (H) = 2.016gEmpirical Molar Mass = 14.032. Solve this equation (below).n = 126.2g substance = 9 Empirical Formula Units (n)--------- 14.03g CH23. After solving for n, multiply the empirical formula.Molecular Formula = 9 (CH2) --> C9H18

### How do you determine the molecular formula of a compound from its empirical formula?

If you are given the empirical formula and are asked for the actual formula, then the molecular mass of the compound will be given too. Take this example problem: Empirical Formula: CH2O Molecular Mass: 180.0 First you have to find the empirical mass. Just find the atomic masses of all the elements in the empirical formula and add them together. If there are multiple atoms of the same element, then you have to add the element's atomic mass for every multiple. In the example, you have to add hydrogen twice because there are two hydrogen atoms in the empirical formula. C- 12.0 H- 1.00 H- 1.00 O- 16.0 + _________ 30.0 The empirical formula is some multiple of the actual formula. The empirical formula shows the ratio of atoms as 1:2:1. This means that the actual formula could be 2:4:2 or 3:6:3 or 4:8:4 etc. In order to find what multiple it is, divide the molecular mass by the empirical mass. An easier way to think of it is: x(empirical mass) = molecular mass Use this formula to find x: x(30.0) = 180.0 x = 6 In this example, x turned out to be exactly 6, but in some cases (especially in lab results) the answer will be close to a whole number but not exact. There is usually a standard +/- .02 for your result. If the x value was 6.02 or 5.98, we would just round up or down as long as it is within .02 Take the x value and multiply it with the number of atoms in the original empirical formula. C1H2O1 * 6 = C6H12C6 The final result is the actual molecular formula.

### Does a formula show the ratio elements in a compound?

depends, an Empirical formula will always (by definition) show the ratio in which atoms are combined within a molecule. a molecular formula on the other hand shows the number of atoms of each element in a molecule, the only exceptions being massive structures, crystal latices and where a molecular formula cannot be produced and is either given in the form n*(empirical formula) or just the empirical formula. do note however that reference to a formula of a molecule usually refer to the molecular formula except in the exceptions listed above.

### How do you calculate the molecular formula of a substance which contain 80 percent C and 20 percent H?

You can only calculate the empirical formula because you do not have a mass of this compound given. To do the empirical formula assume 100 grams and change percent to grams. Get moles. 80 grams Carbon (1 mole C/12.01 grams) = 6.66 moles C 20 grams hydrogen (1 mole H/1.008 grams) = 19.84 moles H the smallest becomes 1 in the empirical formula and the other number is divided by it, Thus; H/C 19.84 moles H/6.66 moles C = 2.9, which we call 3 so, CH3 --------------- is the empirical formula To get the molecular formula tour question needed to read; How to calculate molecular formula from such ans such mass of compound with these percentages of elements, Which, of course, your question did not provide. Then you would have divided that given mass by the mass total of the elements of the empirical formula, got a whole number by which you would have multiplied the numbers of your empirical formula to get molecular formula.

### What is the molecular formula of a compound given the molar mass of the compound is 162.27 grams and the empirical formula is C2H3?

The gram formula unit mass of the empirical formula C2H3 is twice the gram atomic mass of carbon plus three times the gram atomic mass of hydrogen, or about 27. The nearest integer to 162.27/27 is 6. Therefore, the molecular formula for the compound is C12H18.

### What is the empirical formula for a Compound with the molecular formula C16H12CI2O2?

The formula as written, including a capital "I", is already an empirical formula, since it shows a total of 7 carbon atoms and none of the other subscripts is integrally divisible by 7. However, the formula may have been intended to be written C16H12Cl2O2. In that instance, all the subscripts can be integrally divided by 2 to given an empirical formula of C8H6ClO.

### What is the molecular formula of a compound given the molar mass of the compound is 186.5g and the empirical formula is C2H7?

The molecular mass is C2H7 you have 186.5 g of the substance, so calculate 2(12.01)+7(1.01)=31.09 so 186.5/31.09=6 so you can say C12H42 but when you divide 2 by 2 and 7 by 2 you obtain 1 and 3.5 because you have 3.5 you have to multiplied by 2 again, so you obtain the same formula as the empirical formula. It example is the same as water, which empirical formula es H2O as its molecular formula

### What is the empirical formula for C2H6O2?

An empirical formula may be obtained from a molecular formula by dividing all of the subscripts in the formula by every common integral factor of all the subscripts until reaching a collection of subscript numbers that have no common integral factor except the number 1. In the given instance, the only common integral factor is 2; therefore, the empirical formula is CH3O.

### How do you know when to solve for a empirical formula?

If it tells you to find the empirical formula when percent composition is given or if the mass of each element is given in a specific compound.

### What is the empirical formula for C3H5?

The empirical formula is C3H5. The answer does not change from the given form because there is no common denominator to divide by.

### Given a picture of Glucose how do I determine its molecular formula?

Add up or Tally the number of atoms of C, and H, and O and there you have it; namely Glucose = C6, O6, H12 is its molecular formula..

### Which could represent the empirical and the formula of a given compound?

The empirical formula is representative for the chemical composition of a compound; the structural formula is representative for the spatial structure of the compound.

### What alkene has the formula c3h6?

Propene has the given molecular formula.

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