It's very easy. First of all we test the given sample in laboratory to know about its constitution. Let's discuss it by taking an example:-
Suppose the constitution of a compound is given as below:-
C = 92.4%, H = 7.6%
let's assume that the sample is 100 gram. so the weight of carbon is 92.4 gram & that of hydrogen is 7.6 gram. Now it's we must make sure that is the total of weights of constituents 100 or not? If it is not 100, it means there is an another element in the compound, and this is always oxygen in case of hydrocarbons.
Step 1st :- Find out the number of moles of each element
number of moles = weight of the element/Atomic Mass
number of moles of C = 92.4/12 = 7.7 moles
number of moles of H = 7.6/1 = 7.6 mole
Step 2nd:- Find out the relative ratio of the moles:- It is simply done by dividing all by the smallest one
C = 7.7/7.6 = 1.01
H = 7.6/7.6 = 1
Step 3rd:- If the ratio is not whole numbers the multiply all the numbers by a smallest integer number to make them whole numbers.
Here in this case both are nearly whole numbers. so there is need to multiply these numbers.
C = 1
H = 1
Step 4th:- Write the empirical formula
C1H1
step 5th:- Find the weight of empirical formula
1*12 + 1*1 = 13
now if the molecular weight is given then the molecular formula can be written easily.
molecular weight = ( empirical formula weight)n
for example the molecular weight is 78.
n = 78/13 = 6
so the molecular formula is = C6H6
This is possible only after a chemical analysis of this compound.
This is impossible. In order to find this you must know the elements in the compound
The molecular formula is established only after an accurate chemical analysis of the compound.
If you know the molar mass of the compound, you have to calculate the mass of the empirical formula and divide the molar mass of the compound by the mass of the empirical formula in order to find the ratio between the molecular formula and the empirical formula. Then multiply all the atoms by this ratio to find the molecular formula!
The formula of NO2 has a molecular weight of 46 g/mol. Your compound has a molecular weight of 92 g/mol. As you can see the molecular weight of the compound is twice that of the empirical formula. Therefore the molecular formula of your compound is:2 *(NO2) ---> N2O4
The molecular formula mass of this compound is 60.0 amu. The subscripts in the actual molecular formula are 2,4,2.
The molecular formula mass of this compound is 240 amu. The subscripts in the actual molecular formula 8,16,8.
No; the compound with the formula NH4Br is an ionic compound.
The molecular mass of a compound with the formula CH2O is approx. 30, not 120.
Niacin is a molecular compound with the formula C6H5NO2.
The name and the formula of a molecular compound describe the type and the number of atoms in a molecule of the compound.
CH2O is the molecular formula. The name of this compound is formaldehyde.