Limiting & Excess Reagents

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

The limiting reactant . . .

• slows the reaction down.
• is used up first.
• is the reactant that is left over.
• controls the speed of the reaction.

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.

3. The reactant that is not completely used up in a chemical reaction is called the __________ .

• spectator reagent
• limiting reagent
• excess reagent
• catalyst

When you use a balanced chemical equation to calculate the amount of a product on paper it is referred to as the 

• experimental value
• theoretical value
• true amount
• percent yield

Identify the limiting reagent when 6.00 moles HCl combines with 5.00 moles Mg to form MgCl₂.
 
1 Mg +  2 HCl --> 1 MgCl₂  +  1 H₂   
 

• Mg
• H₂
• MgCl₂
• HCl

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.

• AlCl₃
• Cl₂
• Al
• None

Cl₂ + 2 KBr → Br₂ + 2 KCl

How many grams of potassium chloride can be produced from 356 g of Cl₂ and 356 g of potassium bromide?

• 749 g

• 223 g

• 479 g

• 814 g

How many grams of ammonia (NH₃) can be produced from the reaction of 28 g of nitrogen gas and 25 grams of hydrogen gas? 

• 43 g
• 34 moles
• 25 grams
• 34 grams

Which reactant is the limiting reagent and why?

2H₂(g) + O₂(g) → 2H₂O(l)

• Hydrogen is the limiting reagent because two moles of hydrogen is required for every one mole of oxygen to produce two water.

• Oxygen is the limiting reagent because two moles of hydrogen is required for every one mole of oxygen to produce two water.