SAT II Chemistry : Limiting Reagent

Study concepts, example questions & explanations for SAT II Chemistry

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Example Questions

Example Question #1 : Limiting Reagent

Suppose that 8 grams of of hydrogen gas and 16 grams of oxygen gas are ignited. What is the theoretical yield, in grams, of water? Assume hydrogen has an atomic mass of 1 and oxygen has an atomic mass of 16.

Possible Answers:

Correct answer:


First, convert from grams to moles using the molar masses of the compounds. There are 4 mol of hydrogen gas and 0.5 mol of oxygen gas. Oxygen gas is clearly the limiting reagent (since there is more than twice as much hydrogen gas as oxygen gas), which means that the theoretical yield of water is

Water contains two hydrogen atoms and an oxygen atom, so it has a molar mass of

Hence, 1 mol of water would have a mass of 18 g.

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