# Problem: A compound composed of only hydrogen and oxygen is 5.94% hydrogen by mass. The molar mass of this compound is 34.02 g/mol. What is the compound's molecular formula?

###### FREE Expert Solution

We are asked to determine the molecular formula of a compound with a molar mass of 34.2 g/mol and a percentage composition of 5.94% H. The compound is composed only of hydrogen and oxygen.

This means we need to do the following steps:

Step 1: Calculate the mass and moles of O and H in the compound.

Step 2: Determine the lowest whole number ratio of  O and H to get the empirical formula.

Step 3: Get the ratio of the molar mass and empirical mass to determine the molecular formula.

Step 1: The compound is composed of O and H and we’re given the mass percent of H (5.94%)Recall that the mass percentages of a compound must add up to 100%

This means:

Recall that mass percent is given by:

Assuming we have 100 g of the compound, this means we have  94.06 g O and 5.94 g H. Now, we need to get the moles of each element in the compound.

The atomic masses are 15.99 g/mol O and 1 g/mol H.

79% (405 ratings) ###### Problem Details

A compound composed of only hydrogen and oxygen is 5.94% hydrogen by mass. The molar mass of this compound is 34.02 g/mol. What is the compound's molecular formula?