Question

Trisilane (Si3H8) is a liquid with a density of 0.739 g cm-3. It reacts with oxygen to give silicon dioxide (SiO2) and water. Calculate the mass of water that would form if 20.0 cm3 of trisilane reacted completely with excess oxygen.

Answer 1

Answer: The mass of water that would form is 11.52 grams

Explanation:

To calculate the mass of trisilane, we use the equation:

$\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}$

Density of trisilane = $0.739g/cm^3$

Volume of trisilane = $20.0cm^3$

Putting values in above equation, we get:

$0.739g/cm^3=\frac{\text{Mass of trisilane}}{20.0cm^3}\\\\\text{Mass of trisilane}=(0.739g/cm^3\times 20.0cm^3)=14.78g$

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$     .....(1)

Given mass of trisilane = 14.78 g

Molar mass of trisilane = 92.3 g/mol

Putting values in equation 1, we get:

$\text{Moles of trisilane}=\frac{14.78g}{92.3g/mol}=0.160mol$

The chemical equation for the reaction of trisilane and oxygen gas follows:

$Si_3H_8+5O_2\rightarrow 3SiO_2+4H_2O$

By Stoichiometry of the reaction:

1 mole of trisilane produces 4 moles of water

So, 0.160 moles of trisilane will produce = $\frac{4}{1}\times 0.160=0.64mol$ of water

Now, calculating the mass of water by using equation 1, we get:

Moles of water = 0.64 moles

Molar mass of water = 18 g/mol

Putting values in equation 1, we get:

$0.64mol=\frac{\text{Mass of water}}{18g/mol}\\\\\text{Mass of water}=(0.64mol\times 18g/mol)=11.52g$

Hence, the mass of water that would form is 11.52 grams