Part A Binary compounds of alkali metals and hydrogen react with water to produc

Question

Part A Binary compounds of alkali metals and hydrogen react with water to produce H2 (g). The H2 from the reaction of a sample of NaH with an excess of water fills a volume of 0.510 L above the water. The temperature of the gas is 35 Cand the total pressure is 770 mmHg Find the mass of H2 produced Vapor Pressure of Water versus Temperature Temperature Pressure Temperature Pressure ("C) (mnnHg) (°C) 4.58 6.54 921 12.79 17.55 75 23.78 80 31.86 42.23 55.40 95 71.97 92.6 (nnHg) 118.2 149.6 187.5 233.7 289.1 355.1 433.6 525.8 633.9 760.0 Submit 60 65 70 Incorrect; Try Again; 18 attempts remaining 15 20 25 85 Part B 35 Write a balanced chemical equation. Then find the mass of NaH that reacted 45 100 50 Submit Incorrect; Try Again; 19 attempts remaining

Explanation / Answer

The balanced reaction

NaH + H2O = NaOH + H2

vapor pressure water at 35 °C = 42.23 mmHg

pressure of dry H2 gas = Barometric pressure - Vapor pressure of water at 35 C

= 770 - 42.23

= 727.77 mmHg x 1 atm/760 mmHg

= 0.9576 atm

Temperature = 35 + 273 = 308 K

moles of H2 = PV/RT

= 0.9576 atm x 0.510L / 0.0821 L-atm/mol-K x 308K

= 0.0193 mol

Mass of H2 = moles x molecular weight

= 0.0193 x (2*1.008) g/mol

= 0.0389 g

From the stoichiometry of the reaction

Moles of NaH consumed = moles of H2 produced

= 0.0193 mol

mass of NaH = moles x molecular weight

= 0.0193 x 23.9977 g/mol

= 0.4635 g

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