Question

If 5.00 L of hydrogen gas measured at 20.0*C and 80.1 kPa is burned in an excess of oxygen, what mass under the same conditions, would be consumed?

Answer 1

The mass of `"H"_2"` consumed is `"0.331 g H"_2"`.

Explanation:

Use the equation for the ideal gas law to find the moles of hydrogen gas. Then determine the mass by multiplying the moles by its molar mass.

Ideal gas law

`PV=nRT`

Known

`P="80.1 kPa"`

`V="5.00 L"`

`R="8.31447 L kPa K"^(-1) "mol"^(-1)`

`T="20.0"^@"C + 273.15"="293.2 K"`

Unknown

moles, `n`

To determine moles `"H"_2"`, rearrange the equation to isolate `n`. Plug in the known values and solve.

`n=(PV)/(RT)`

`n=(80.1color(red)cancel(color(black)("kPa"))xx5.00color(red)cancel(color(black)("L")))/(8.31447color(red)cancel(color(black)("L")) color(red)cancel(color(black)("kPa")) color(red)cancel(color(black)("K"))^(-1) "mol"^(-1)xx293.2color(red)cancel(color(black)("K")))="0.164 mol H"_2"`

To determine the mass of `"H"_2"` by multiplying the moles by its molar mass `("2.016 g/mol")`.

`0.164color(red)cancel(color(black)("mol H"_2))xx(2.016"g H"_2)/(1color(red)cancel(color(black)("mol H"_2)))="0.331 g H"_2"`