# What is the molecular formula of a material for which complete combustion of a unknown mass gives #3.38*g# of #CO_2(g)#, and #0.69*g# of water. An #11.6*g# mass of this gas gives a volume of #10.0*L# at #0# #""^@C# of #10*L#?

##### 2 Answers

#### Answer:

You probably have......

#### Explanation:

We can only interrogate the molecular formula on the basis of the Ideal Gas equation. The combustion data that you gave us were non-kosher (neither the mass of the combusted gas, nor the water content of the combustions were included).

If

OR

Now this molecular mass is consistent with that of

Anyway, I don't think you have included all of the data for this question.

Had we calculated as molecular mass of

#### Answer:

The molecular formula is

#### Explanation:

This is an empirical formula/molecular formula problem.

**(a)** Calculate the moles of

**(b)** Calculate the moles of

I assume that you meant 0.69 g of water.

**(c)** Find the molar ratios.

From here on, I like to summarize the calculations in a table.

The empirical formula is

**(d)** Calculate the molar mass of the gas

You don’t give the pressure or temperature of the gas, so I will assume STP (1 bar and 0 °C).

**(d)** Calculate the formula of the gas

The empirical formula mass of

The molecular mass of the gas is 26.3 u.

The molecular mass must be an integral multiple of the empirical formula mass.

The molecular formula must be twice the empirical formula.