Exercises
Exercise 1. Carbon suboxide is a compound made up of carbon and oxygen. There is also carbon monoxide, CO, and carbon dioxide, CO2. If a 5.00 g sample of carbon suboxide contains 2.64 g of C and 2.36 g of O, show the law of multiple proportions is adhered to. What is a possible formula for carbon suboxide?
For carbon suboxide, 2.64g/2.36g = 1.12
Divide the amount of carbon and oxygen by its molecular mass
\(\displaystyle \frac{2.64g}{12.011g/mol}=0.2198\;mol\;C\;\;\;\frac{2.36 g}{15.9994g/mol}=0.1475 mol\;O\)
\(\displaystyle C_{0.2198}O_{0.1475}\)
Whole numbers are needed for the subscripts. Divide both subscripts by 0.1475.
\(\displaystyle C_\frac{0.2198}{0.1475}O_\frac{0.1475}{0.1475}\;\;\;=\;C_{1.49}O\)
Multiply the subscripts by an integer to get rid of the decimal. If we multiply by 2, we get C3O2 as a possible formula for carbon suboxide.
Exercise 2. Two compounds that contain nitrogen and oxygen have the following percent composition by mass.
Compound 1: 30.4% N and 69.6% O
Compound 2: 22.6% N and 77.4% O
Show the law of multiple proportions is followed. What is the formula of the second compound if the formula of the first compound is NO2?
Exercise 3. A sample of 22.65 g of silicon tetrachloride, SiCl4, reacts with 10.25 g of water, H2O. The products, silicon dioxide and HCl, have a total mass of 27.45 g. How much water is left unreacted?