Stoichiometry/Limiting/Excess/Percent Yield

The ______________ yield is the maximum amount of product possible in a reaction. This determines the amount of product that should be produced in a perfect setting

• limiting

• actual
• excess

• theoretical

Answer explanation

Limiting = the reactant that runs out

Excess = the reactant that is left over when rxn stops

Theoretical = how much product you should make

Actual = how much product you actually make

Tags

NGSS.HS-PS1-6

When reacting Na with Cl₂, we calculated that the theoretical yield should be 13 grams. Our actual yield was 12.5 grams. What is the percent yield?

• 90.4%

• 104%

• 96%

• 1.0%

Answer explanation

Tags

NGSS.HS-PS1-7

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

• 1.2%

• 120%

• 85%
• 76%

Answer explanation

What does percent yield indicate?

• The amount of product we should get
• The efficiency of the lab
• The amount of product we actually got
• nothing

Answer explanation

% Yield tells the efficiency of your work - how close you were to the theoretical value you should have gotten

Some product may be lost during filtering causing your actual yield to be less than your theoretical yield.

• true

• false

Answer explanation

Anytime you "lose" product, your actual will be less than your theoretical b/c you lost some of the product.

Your actual will be higher than your theoretical if you add substances that are not the product - example measuring the filter paper & product, and not just the product.

Tags

NGSS.MS-PS1-5

What is a limiting reactant?

• the reactant that determines how much product can be made
• the reactant that is in excess
• the product that you can make the most of
• the amount of reactants that react with each other

Answer explanation

The limiting reactant LIMITS the amount of product that can be made, b/c the rxn stops when the limiting runs out...meaning no more product is made.

You need 1 screen, 2 speakers, and 3 buttons to build a television.  If you have 7 screens, 7 speakers, and 12 buttons, what is the limiting item?

• screen

• speaker

• button

• television

Answer explanation

It takes 3 buttons to make a TV, you have 12 - so theoretically you can make 4 TVs (12/3=4)

It takes 2 speakers to make a TV, you have 7 - so theoretically you can make 3 TVs (7/2=3.5)

It takes 1 screen to make a TV, you have 7 - so theoretically you can make 7 TVs (7/1=7)

Tags

NGSS.HS-ETS1-2

When 12 moles of O₂ reacts with 1.1 mole of C₁₀H₈ what is the limiting reactant?  C₁₀H₈ + 12 O₂ --> 10 CO₂ + 4 H₂O

• Oxygen
• C₁₀H₈
• Water
• Carbon Dioxide

Answer explanation

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

Answer explanation

the limiting is used up first and stops/limits the reaction from continuing.

Tags

NGSS.HS-PS1-7

1 Cheese + 2 Bread --> 1 grilled cheese

How many grilled cheeses can you make with 26 slices of bread and 14 pieces of cheese?

• 14

• 13

• 26

Answer explanation

You can make 13 b/c of the bread - 26/2 = 13

cheese - 14/1 = 14