Homework Help: chemistry

Posted by Miley on Tuesday, June 10, 2008 at 8:48pm.

Hydrogen gas is produced when zinc reacts with hydrochloric acid. if the actual yeild of this reaction is 85%, how many grams of zinc are needed to produce 112L of H2 at STP?

chemistry - GK, Tuesday, June 10, 2008 at 9:35pm
The reaction is:
Zn + 2HCl --> ZnCl2 + H2
1 mole of any gas at STP is 22.4 L
112L of H2 / 22.4 L/mol = 5 moles H2
(5 mol H2)(1 mol Zn / 1 mol H2) = 5 moles of Zn
The above relationship assumes that the reaction is 100% efficient. Since the reaction is only 85% efficient, MORE than 5 moles of Zn must be used. I will let you figure that part out on your own. [The multiplier you use has to do with the relationship of 100% to 85%]
- chemistry - Miley, Tuesday, June 10, 2008 at 9:44pm
  i don't get what to do next, can you please show me??
  - chemistry - GK, Tuesday, June 10, 2008 at 9:55pm
    multiply the 5 moles of zinc by the factor:
    (1.00/0.85)
  - chemistry - Miley, Tuesday, June 10, 2008 at 10:02pm
    then what do i do??
    - chemistry - DrBob222, Wednesday, June 11, 2008 at 12:00am
      5 mols Zn x (100/85) = ?? mols Zn
      You want grams, Convert mols Zn to grams by grams = mols x molar mass.
chemistry - john, Monday, May 16, 2011 at 10:40am
380

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