Limiting/Excess and Molar Mass/Ratio

The limiting reactant

• slows the reaction down

• is used up first

• is the reactant that is left over

• controls the speed of the reaction

Use the equation 2 Al + 3 Cl₂ ---> 2 AlCl₃.  If 2 moles of aluminum and 2 moles of chlorine are reacted, identify the limiting reactant.

• Al

When does a chemical reaction stop?

• When the lab is finished

• When the excess reactant is used up

• When the limiting reactant is used up

• Chemical reactions never stop

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What is the limiting reactant if 10 moles of NH₃  react  with 30.0 moles of NO? 4NH₃+6NO --> 5N₂ + 6H₂O

• NH₃

• NO

• N₂

• water

Theoretical yield = 73g Actual yield = 62g Calculate the percent yield.

percent yield= (actual/theoretical)

• 1.16%

• 116%

• 85%

• 76%

4NH₃ + 5O₂ --> 4NO + 6H₂O

How many grams of NO are formed if 6.30g of ammonia react with 1.80g of oxygen?

• 0.37 g NO

• 11.1 g NO

• 0.045 g NO

• 1.35 g NO

You need 2 pieces of bread, 1 tablespoon of peanut butter and 2 tablespoons of jelly to make a sandwich.  If you have 10 pieces of bread, 4 tablespoons of peanut butter and 20 tablespoons of jelly, what is the limiting reactant?

• bread

• jelly

• peanut butter

• sandwich

Use the balanced equation to answer the following question.

3 Ba(NO₃)₂ + 2 Na₃PO₄ --> Ba₃(PO₄)₂ + 6 NaNO₃

i. 3 Ba(NO₃)₂ : 3 Ba(NO₃)₂ ii. 3 Ba(NO₃)₂ : 2 Na₃PO₄

iii. 3 Ba(NO₃)₂ : 1 Ba₃(PO₄)₂ iv. 3 Ba(NO₃)₂ : 6 NaNO₃

What are the possible molar ratios for 3 Ba(NO₃)₂ in the following equation?

• I and II

• III and IV

• I, II, III, and IV

• II, III, and IV

Use the balanced equation to answer the following question.

2 FeCl₃ + MgO --> Fe₂O₃ + 3 MgCl₂

How many moles of iron chloride (FeCl₃) will be produced from 5.50 moles of magnesium oxide (MgO)?

(1 step, molar ratio question)

• 5.50 mol FeCl₃

• 11.0 mol FeCl₃

• 2.25 mol FeCl₃

• 3.67 mol FeCl₃

Use the balanced equation to answer the following question:

2 C₂H₆ + 7 O₂ --> 4 CO₂ + 6 H₂O

Given 8.25 grams of ethane (C₂H₆), how many moles of carbon dioxide (CO₂) will be produced?

(2 step railroad, molar mass -> molar ratio)

• 0.27 mol CO₂

• 0.549 mol CO₂

• 16.5 mol CO₂

• 0.405 mol CO₂