Stoichiometry 2025

Open Ended

Why is the study of stoichiometry significant in understanding chemical reactions?

Multiple Choice

Choose which type of conversion is needed.

How many moles of water are in 24.3g of water?

• particles to moles

• grams to moles

• moles to moles

• moles to grams

Multiple Choice

What is Avogadro's number and what does it represent?

• 6.02 x 10^23, the number of particles in one mole

• 12, the mass of one mole of carbon-12

• 18.0, the mass of one mole of water

• 40.08, the mass of one mole of calcium

Multiple Select

Which of the following statements about moles are correct?

• Moles connect the number of particles to grams.

• Moles are calculated using Avogadro's number.

• Moles are only used for solids.

• Moles can be used to convert between grams and particles.

Multiple Choice

How many particles (atoms) are in 13.5 grams of Beryllium?

• 1.50 particles

• 9.03 particles

• 4.00x10²³ particles

• 9.03x10²³ particles

Fill in the Blank

The molar mass of CaCl2 is ___ g/mol.

Open Ended

Explain the steps you would take to calculate the molar mass of a compound given its chemical formula.

Fill in the Blank

How many moles of aluminum are in the following molecule?

$$Al\left(NO_3\right)_3$$

Fill in the Blank

How many nitrogen atoms are in the following molecule?

$$Al\left(NO_3\right)_3$$

Multiple Choice

Calculate the molar mass for Al(OH)₃

• 78.0 g/mol

• 72 g/mol

• 28 g/mol

• 25 g/mol

Multiple Choice

How many eggs would you need to make 9 dozen cookies according to the recipe?

• 6 eggs

• 9 eggs

• 12 eggs

• 18 eggs

Multiple Choice

How many cups of chocalate chips are needed to product 48 cookies?

• 1.3

• 2.7

• 16

• 4

Multiple Choice

In what ways are recipes for chocolate chip cookies similar to balanced chemical equations in chemistry?

• Both use moles as units for ingredients.

• Both require precise measurements of ingredients.

• Both are used only in baking.

• Both involve chemical reactions that produce cookies.

Drag and Drop

Balance the following equation.

$$H_2+N_2\ \rightarrow\ NH_3$$

(Drag and drop the correct coefficient in front of each element.)

​

Placeholder

H₂ + ​

Placeholder

N₂ → ​

Placeholder

NH₃

Drag these tiles and drop them in the correct blank above

3

1

2

4

5

Drag and Drop

Balance the following equation.

$$Fe+Br_2\ \rightarrow\ FeBr_3$$

(Drag & drop the correct coefficient in front of each element.)

​

Placeholder

Fe + ​

Placeholder

Br₂ → ​

Placeholder

FeBr₃

Drag these tiles and drop them in the correct blank above

1

2

3

4

5

Multiple Choice

According to Antoine Lavoisier, what fundamental principle is essential for performing chemical experiments?

• Law of Conservation of Mass

• Law of Definite Proportions

• Law of Multiple Proportions

• Law of Constant Composition

Multiple Choice

Which of the following statements about the mole is correct?

• 1 mole equals 6.022 x 10^23 particles and also equals grams on the periodic table.

• 1 mole equals 6.022 x 10^23 grams.

• 1 mole equals the number of molecules only.

• 1 mole equals the number of atoms only.

Multiple Choice

Why is the mole necessary when converting between grams of reactants and products in a chemical reaction?

• Because grams of reactants and products cannot be directly related without using the mole.

• Because the mole is always larger than a gram.

• Because the mole is only used for gases.

• Because grams and moles are the same unit.

Multiple Choice

What is the first thing you must do to solve a stoichiometry problem?

• Write a Balanced Equation
• Panic
• Write an Unbalanced Equation
• Ask for help

Open Ended

Explain how a mole ratio is used as a conversion factor in stoichiometry.

Multiple Choice

Given the balanced equation 2H₂ + O₂ → 2H₂O, what is the mole ratio of hydrogen to oxygen?

• 2:1

• 1:2

• 1:1

• 2:2

Multiple Choice

Select the correct molar ratio taken from this balanced equation:

1 N­₂ + 3 H₂ --> 2 NH₃

• 1 N­₂ = 3 H₂

• 1 mol N­₂ = 2 mol NH₃

• 2 mol N­₂ = 1 mol NH₃

• 3 mol N­₂ = 3 mol NH₃

Multiple Choice

Select the correct molar ratio taken from this balanced equation:

4 Al + 3 O₂ --> 2 Al₂O₃

• 1 mol Al = 1 mol Al₂O₃

• 4 Al = 2 Al₂O₃

• 4 mol Al = 2 mol Al₂O₃

• 4 mol Al = 2 mol Al

Multiple Choice

Select the coefficients that correctly balance the following skeleton equation:

__ H₂O --> __ H₂ + __ O₂

• 2 --> 2, 1

• 1 --> 1, 2

• 4 --> 2, 2

• 2 --> 2, 4

Fill in the Blank

What if you had 3 moles of oxygen, how much hydrogen would you need to react and how much water would you get?

Multiple Choice

Which of the following is NOT a type of stoichiometry problem listed?

• Mole A to Mole B

• Mass A to Mole B

• Limiting Reactant

• Mole C to Mole D

Fill in the Blank

In the reaction 4NH3 + 5O2 → 6H2O + 4NO, using 0.176 mol O2 produces ___ mol H2O.

Multiple Choice

Given the equation N2 + 3H2 → 2NH3, how many moles of NH3 are produced from 5 moles of N2?

• 10 moles

• 5 moles

• 15 moles

• 2 moles

Fill in the Blank

Consider the balanced equation.

$$C_5H_{12}+8O_2\ \rightarrow\ 5CO_2+6H_2O$$

If 4 moles of O₂ are used instead, how many moles of H₂O will be produced?

Fill in the Blank

Consider the balanced equation:

$$C_5H_{12}+8O_2\ \rightarrow\ 5CO_2+6H_2O$$

If 2 moles of C₅H₁₂ are used instead, how many moles of O₂ will be required?

Multiple Choice

What is the main purpose of using a balanced chemical equation in mole-to-mole conversions?

• To ensure the correct mole ratios are used in calculations

• To identify the limiting reactant

• To determine the physical state of reactants and products

• To calculate the mass of products directly

Open Ended

Explain how mole ratios are used to convert between different reactants and products in a chemical reaction. Provide an example.

Multiple Select

Which of the following steps are necessary to convert grams of substance A to grams of substance B in a chemical reaction?

• Use the molar mass of A

• Use the coefficients from the balanced equation

• Use the molar mass of B

• Use the density of A

Multiple Choice

According to the diagrams, what role do moles play in chemical reactions?

• They provide a bridge between reactants and products

• They determine the color of the products

• They are only used for gases

• They are not necessary for calculations

Multiple Choice

What is the mass of H2O produced when 1.9 mol of NH3 reacts with excess O2 according to the equation 4NH3 + 5O2 → 6H2O + 4NO?

• 51 g

• 34 g

• 21 g

• 60 g

Multiple Choice

How many grams of NO are produced if 12 g of O2 is combined with excess ammonia in the reaction 4NH3 + 5O2 → 6H2O + 4NO?

• 9.0 g

• 6.0 g

• 12.0 g

• 15.0 g

Open Ended

How does the Law of Conservation of Mass relate to stoichiometry in chemical reactions?

Open Ended

Explain the step-by-step process for determining the grams of water produced when a given mass of oxygen reacts with ammonia, as described in the images.

Fill in the Blank

Fill in the blank: According to the balanced equation 4NH3 + 5O2 → 4NO + 6H2O, the molar mass of O2 used in the calculations is ___ g/mol.

Multiple Select

Which of the following steps are necessary to determine the moles of oxygen needed to produce a given mass of nitrogen monoxide?

• Convert grams of NO to moles of NO

• Use the mole ratio from the balanced equation

• Convert moles of O2 to grams of O2

• Convert grams of O2 to moles of O2

Open Ended

What is the significance of 'excess' in stoichiometry problems, and how does it affect the calculation of product mass?

Multiple Choice

In this image, what are the information in red is called the_______.

• Product
• Reactant
• Chemical Subscript
• Yield

Multiple Choice

The limiting reactant

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

Multiple Choice

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

Multiple Choice

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

Multiple Choice

The diagram below represents H₂ and Cl₂ molecules that will potentially react to form HCl. Which of the following best describes this reaction?

• The limiting reactant is chlorine.

• The limiting reactant is hydrogen.

• Hydrogen and chlorine are nonreactive.

• All molecules shown will react to form the product. 

Multiple Choice

According to Antoine Lavoisier, what remains constant before and after a chemical experiment?

• The amount of matter

• The temperature

• The color of substances

• The volume of gases

Multiple Choice

What is the formula for percent yield?

• $$\frac{Actual}{Theoretical}\times100$$
  

• $$\frac{Theoretical}{Actual}\times100$$
  

• $$\frac{Actual\times Theoretical}{100}$$

• $$\frac{100}{Actual\times Theoretical}$$

Multiple Choice

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

• Percent
• actual
• stoichiometry
• theoretical

Multiple Choice

Which of the following do you get through measuring its mass? (No calculations)

• percent yield
• theoretical yield
• actual yield
• limiting reagent

Multiple Choice

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

• 1.16%
• 116%
• 85%
• 76%

Multiple Choice

The theoretical yield of a reaction is 237 grams, but the reaction actually yields 26 less grams than expected. What is the percent yield?

• 17.6%

• 82.4%

• 89.0%

• 121.3%

Multiple Choice

CH₄  +  2O₂  →  CO₂  +  2H₂O
24 grams of CH₄ was added to the above reaction. Calculate the theoretical yield of CO₂.

• 66 grams
• 132 grams
• 33 grams
• 8.72

Multiple Choice

2Fe₂O₃ + C → Fe + 3CO₂

You add 28 grams of carbon. You find the actual yield to be 181.2 grams of CO₂. What is the percent yield of CO₂? (Hint: calculate theoretical yield of CO₂ first)

• 58.83%

• 308%

• 6435%

• 15.5