Hydrogen gas can be produced by the reaction of aluminum metal with hydrochloric

Question

Hydrogen gas can be produced by the reaction of aluminum metal with hydrochloric acid according to the following reaction: 2Al (s) + 6 HCl (aq) 2AlCl3 (aq) + 3 H2 (g) A student collected 35.5 mL of dry H2(g) gas at 26.0 °C and at a pressure of 755 mmHg.

a) What is the pressure of dry H2 gas in bar?

b) Calculate the mass of Al required to form 10.0 L of H2.

c) Identify which species is the oxidizing agent and which is the reducing agent.

Oxidizing agent:______________________

Reducing agent:______________________

Explanation / Answer

a)

to convert the pressure unit from mmHg into bar uses the following expression:

1 bar = 750.064 mmHg

755 mmHg (mmHg) *1 bar /750.064 mmHg

= 1.00658 Bar

b)

first calculate the number of moles in 10.0 L of H2 as follows:

PV= nRT

P = 1.00658 Bar or 0.99 atm

V= 10.0 L , R= 0.0821 L-atm / mol K, T = 26.0 °C or 299 K

n= PV/RT

n= 0.99 atm*10.0 L /.0821 L-atm / mol K *299 K

n= 0.40 mol Hydrogen

Now calculate the moles of Al as follows:

2Al (s) + 6 HCl (aq) 2AlCl3 (aq) + 3 H2 (g)

2 mol Al /3 mol H2 *0.40 mol H2 = 0.267 mol Al

Now calculate the mass of Al by its molar mass:

molar mass of Al = 26.98 g/mol

0.267 mol Al*26.98 g/mol= 7.20 g

c)

Oxidation:

Oxidation is a process in which either 1 or all following changes occurs:

Reduction:

Reduction is a process in which either 1 or all following changes occurs:

Oxidizing agent:

Oxidizing agent is a reactant of a reaction which causes an oxidation through accepting electron.

Reducing agent:

Reducing agent is a reactant of a reaction which causes a reduction through donating electron.

2Al (s) + 6 HCl (aq) 2AlCl3 (aq) + 3 H2 (g)

Oxidizing agent:__ HCl

Reducing agent:__ Al

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