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B_2 H_6 B_4 H_10 B_5 H_9 B_6 H_10 B_10 H_14 Acetaldehyde is a common liquid comp

ID: 1010316 • Letter: B

Question

B_2 H_6 B_4 H_10 B_5 H_9 B_6 H_10 B_10 H_14 Acetaldehyde is a common liquid compound that vaporizes readily. Determine the molar mass of acetaldehyde from the following data: Sample mass = 0.107 g Volume of gas = 125 mL Temperature = 0.0 degree C Pressure = 331 mm Hg Iron reacts with hydrochloric acid to produce iron(II) chloride and hydrogen gas: Fe(s) + 2 HCl(aq) rightarrow FeCl_2 (aq) + H_2(g) The H_2 gas from the reaction of 2.2 g of iron with excess acid is collected in a 10.0-L flask at 25 degree C. What is the pressure of the H_2 gas in this flask?

Explanation / Answer

Fe + 2HCl ------> FeCl2 + H2

1 mole of Fe react with HCl to gives 1 mole of H2

56g of Fe react with HCl to gives 2g of H2

2.2 g of Fe react with HCl to gives = 2*2.2/56 = 0.0785g of H2

PV   = nRT

n = W/M

PV   = WRT/M

W = 0.0785g

M   = 2

R = 0.0821L-atm/mole-K

T = 25C0 = 25+273= 298K

V = 10L

P = WRT/VM

    = 0.0785*0.0821*298/10*2 = 0.096atm >>>> answer