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Homework Help: Limiting Reactant and gases

  1. Nov 27, 2009 #1
    1. The problem statement, all variables and given/known data
    3.50 g of magnesium metal is added to 100. mL of 2.00 M aqueous hydrochloric acid. The substances react to completion, producing aqueous magnesium chloride and hydrogen gas (H2). How many liters of pure hydrogen gas, measured at 0.00oC and 1.00 atm are produced in this reaction?

    2. Relevant equations

    3. The attempt at a solution
    Rxn Eq: 2Mg + 2HCl --> 2MgCl + H2

    3.5 g Mg x (1 mol/24.3g) = .144 mol Mg
    2 mol/L HCl x .1L = .2 mol HCl
    Mg is limiting reactant

    .144 mol Mg x (1 mol H2/2 mol Mg) = .072 mol H2

    V=(nRT)/P=[(.072)(.08206)(273)] / 1 = 1.61 L H2

    It says the answer is 2.24L?
  2. jcsd
  3. Nov 28, 2009 #2


    User Avatar

    Staff: Mentor

    What is formula of magnesium chloride?

    Hint: which periodic table group?

  4. Nov 28, 2009 #3
    WOW! I can't believe I missed that. I always miss these on minor mistakes that don't even have to do with the difficult part... Thanks
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