Question

What is the percent of hydrogen by mass in HNO3?

Answer 1

the percent of hydrogen by mass in HNO3 is 1.600%

Answer 2

Answer:

$\boxed {\boxed {\sf 1.5996953 \%\ or \ 1.6 \%}}$

Explanation:

Percent composition tells us the mass percentage of an element in a compound. It can be found by dividing the mass of the element by the mass of the compound, then multiplying by 100.

$\frac{element \ mass}{compound \ mass} *100$

1. Compound Mass

The compound given is HNO₃

• Hydrogen (H) and Nitrogen (N) have no subscript, implying there is 1 atom of each element.
• Oxygen (O) has a subscript of 3, so there are 3 atoms.

Use the Periodic Table to find the masses of each element.

• Hydrogen: 1.008 u
• Nitrogen: 14.007 u
• Oxygen: 15.999 u

Next, multiply each element's mass by the number of atoms, then add them together.

• (1.008 u) + (14.007 u) +  (3 * 15.999 u)
• 63.012 u

2. Percent Composition

Now we know that HNO₃'s mass is 63.012 u. This is the compound mass.

We want to find the percent of hydrogen and its mass is 1.008 u. This is the element mass.

$\frac{1.008 \ u }{63.012\ u } *100$

$0.015996953*100$

$1.5996953$

This can be rounded to the nearest tenth. The 9 in the hundredth place tells us to round the 5 to a 6.

$\approx 1.6$

The percent of hydrogen in HNO₃ is 1.5996953% or about 1.6%