# A compound has an empirical formula of HCO_2 and a molecular mass of 90 grams per mole. What is the molecular formula of this compound?

##### 1 Answer
Feb 25, 2016

The molecular formula is always a multiple of the empirical formula: ("empirical formula")_n ="molecular formula".

#### Explanation:

So $\left(1.00794 + 12.011 + 2 \times 15.999\right) \cdot g \cdot m o {l}^{-} 1 \times n$ $=$ $90 \cdot g \cdot m o {l}^{-} 1$.

We solve for $n$, and clearly $n$ $=$ $2$.

So empirical formula is ${C}_{2} {H}_{2} {O}_{4}$.