Question

What is the mass of hydrogen in 50.0 g of propane, C3H8?

9.1 g


44.0 g


18.2 g


81.8 g

Answer 1

The atomic molar mass of C is 12 and of H is 1. Hence the mass ratio of H to the molecule is 8/(8+36) = 2/11

Since 50*2/11 ≈ 9, the answer is B.

Answer 2

Answer: 9.1 g

Step-by-step explanation:

To calculate the moles, we use the equation:

`\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}`

For
`C_3H_8`

Given mass = 50.0 g

Molar volume of
`C_3H_8` = 44 g/mol

Putting values in above equation, we get:

`\text{Moles of}C_3H_8=(50)/(44)=1.14mol`

According to avogadro's law, 1 mole of every substance weighs equal to the molecular mass and contains avogadro's number
`6.023* 10^(23)` of particles.

1 mole of
`C_3H_8` contains 8 moles of hydrogen

1.14 moles of
`C_3H_8` contains =
`(8)/(1)* 1.14=9.1` moles of hydrogen

Mass of hydrogen=
`moles* {\text {molar mass}}=9.1* 1.0=9.1 g`

Thus the mass of hydrogen is 9.1 grams.