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?

🤓 Based on our data, we think this question is relevant for Professor Johnson's class at Southwestern Oklahoma State University.

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:


100% = mass% O + mass% Hmass % O = 100% - mass % Hmass % O = 100% - 5.94%mass % O= 94.06% O


Recall that mass percent is given by:

%mass = mass XTotal massx100


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.


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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?

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Empirical Formula concept. You can view video lessons to learn Empirical Formula. Or if you need more Empirical Formula practice, you can also practice Empirical Formula practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Johnson's class at Southwestern Oklahoma State University.