Limiting Reactants

6. If you had 17.3 g of hydrogen and 8.91 g of oxygen, which is the limiting reactant, and how
many grams of water could you produce?
17.3 g H2
2.02 g/mol
8.91 g O2
32.0 g/mol
=
=
8.56 moles H
2
0.278 moles O
2
The O 2 is the limiting reactant in this case and 0.557 mole water or
0.557 g water × 18 g/mol = 10.0 g water would be produced.
Problems
1. Cisplatin is an antitumor agent. It has the molecular formula Pt(NH 3 ) 2 Cl 2 . How many grams of
cisplatin can be produced if the limiting reactant is 1 kg of platinum?
1000 g Pt
195.08 g/mole =
5.126 mole Pt
1 mole Pt(NH
5.126 mole Pt
3 ) 2Cl
×
2 300.0474 g
×
1 mole Pt 1 mole Pt(NH 3 ) 2Cl2
=
1538 g Pt(NH 3 ) 2Cl 2 produced.
2. Hydrogen cyanide is used in the production of cyanimid fertilizers. It is produced by the
following reaction.
2 CH 4 + 2 NH 3 + 3 O 2 2 HCN + 6 H 2 O
a) How much hydrogen cyanide can be produced starting with 100 kg of each of the
reactants?
100 kg CH 4 = 6233 mol CH 4
100 kg NH 3 = 5872 mol NH 3 ,
100 kg O 2 = 3125 mol O 2
Look at the ratios
6233
methane:
2
= 3117
5872
ammonia:
2
= 2936
3125
oxygen:
3
= 1042
2/3 of 3125 mol can be produced = 2083 mol of hydrogen cyanide, which is 56.3 kg HCN.
b) Which is the limiting reactant?
The smallest ratio is for oxygen, so the limiting reactant is oxygen.
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Foundations of Chemistry