Question

1. Some commercial drain cleaners contain a mixture of sodium hydroxide and aluminum powder. When the mixture is poured down a clogged drain, the following reaction occurs: 2NaOH(aq) + 2Al(s) + 6H2O(l) → 2NaAl(OH)4(aq) + 3H2(g) The heat generated in this reaction helps melt away obstructions such as grease, and the hydrogen gas released stirs up the solids clogging the drain. Calculate the volume of H2 formed at 25.5°C and 1.00 atm if 3.75 g of Al is treated with an excess of NaOH.

2. When ammonium nitrite (NH4NO2) is heated, it decomposes to liquid water and nitrogen gas. This property is used to inflate some tennis balls. (a) Write a balanced equation for the reaction. Include phase symbols. NH4NO2(s) → ___ (b) Calculate the quantity (in grams) of NH4NO2 needed to inflate a tennis ball to a volume of 74.59 mL at 1.63 atm and 22°C. Assume the volume of water produced is negligible.

Answer 1

1) Strategy 1) find the number of moles of Al 2)find the number of moles of H2 3)Find the volume of H2

3.75 g x 1 mol/ 26.98 g = 0.139 moles Al

0.139 moles Al x 2 moles H2 / 2 moles Al = 0.116 moles H2

V = nRT /P = 0.116 moles x 0.0802 L atm/ K mol x (273 + 25.5 K) / 1 atm
V = 2.77 L (2 sf)

2) a)

NH4NO2(s) —heat→ N2(g) + 2H2O(g)

b)Assuming the N2 is the only gas used to fill the ball, calculate the amount required.

pV = nRT

p = 1.63atm, V = 74.59 mL = 0.07459 L, R = 0.08206 atm L/mol K, T = 22°C = 295.15 K

n = pV/RT = 1.63×0.07459/0.08206×295.15 = 0.00501 moles N2 gas required.

Since 1 mole of NH4NO2 releases 1 mole of N2 gas, 0.00501 moles NH4NO2 is required.

Mr of NH4NO2 = 64, so 0.00501×64 = 0.32064 grams NH4NO2.