Calculate how many grams of sodium azide (NaN3) are needed to inflate a 25.0 × 25.0 × 20.0 cm bag to a pressure of 1.25 atm at a temperature of 20.0°C. How much sodium azide is needed if the air bag must produce the same pressure at 10.0°C?

20.0°C:

_______ g NaN3

1 answer

Were you given an equation for the decomposition? If so, make sure it agrees with what I've written; otherwise I will use this one.
2NaN3 ==> 2Na + 3N2
volume of bag is 25 x 25 x 20 = approx approx 13,000 cc or about 13 L but you need a better answer than this estimate. All numbers below this one are estimates also.

Use PV = nRT. You know P, V, R and T (must be in kelvin). Solve for n = mols. That will be mols N2.

Use the coefficients in the balanced equation to convert mols N2 to mols NaN3. You can see that 3 mols N2 need 2 mols NaN3.

Then grams NaN3 = mols NaN3 x molar mass NaN3.

Do the same procedure for the second part of the problem.

Post your work if you get stuck.