Limiting 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

Tags

NGSS.HS-PS1-7

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.

Tags

NGSS.HS-PS1-5

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

• spectator reagent
• limiting reagent
• excess reagent
• catalyst

Tags

NGSS.HS-PS1-7

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

Tags

NGSS.HS-PS1-7

Why is it important to identify the limiting reagent?

• The limiting reagent speeds up the reaction.

• The limiting reagent controls the amount of product formed.

• If there is no limiting reagent, the reaction will not occur.

• No stoichiometry calculations can be done without a limiting reagent.

Tags

NGSS.HS-PS1-7

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

Tags

NGSS.HS-PS1-7

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

Tags

NGSS.HS-PS1-7

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.

Theoretical yield = 73g

Actual yield = 62g

Calculate the percent yield.

• 116%

• 85%

• 1.16%

• 76%

Tags

NGSS.HS-PS1-7