Stoichiometry Gizmo Answer Key

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Gizmo is a learning platform that allows students to learn math and science, giving them something to measure, graph and compare. One of the science subjects that the students will learn through Gizmo is Stoichiometry. Stoichiometry is commonly introduced once discussing parts of the atom and unit conversions.

After learning Stoichiometry, you will be required to take the Stoichiometry exam to test your ability to determine recipes in chemical reactions. If you’re accidentally taking the Stoichiometry test and need the answer in order to pass the test, you will find them through our post below!

Stoichiometry Gizmo Answer Key

Stoichiometry Gizmo Answers!

We will show you the answers to the Stoichiometry Gizmo test from The correct answer is highlighted in bold font.

When taking Stoichiometry test, you will see the new equitation as follow:

Fe2O3 (s) + 3CO (g) →2Fe (s) + 3CO2 (g)

With the new question as follow:

‘How many moles of carbon monoxide (CO) are required to react completely with 1.75 moles of iron (III) oxide (Fe2O3)?’

Problem solved: 0


  1. Look at the coefficients(such as the “3” in 3CO) in front of each substance in the equation. The coefficients tell you how many molecules or atoms take part in a chemical reaction. In the spaces below, list the number of each molecule or atom in the equation:



CO _3_

Fe _2_

CO2 _3_

  1. In a balanced equation, the same number of each kind of atom is shown on each side of the equation. Calculate the number of iron (Fe), oxygen (O), and carbon atoms (C).


Reactants Iron: _2_ Oxygen: _6_ Carbon: _3_

Products Iron: _2_ Oxygen: _6_ Carbon: _3_

Based on these values, is the equation balanced?


The students need to check if the equitation is still: Fe2O3+ 3CO →2Fe + 3CO2. If not, they can click ‘New Equitation’ until it reappears.


A mole is:

A)A mammal known for digging up gardens.

B)A small, dark spot on the skin.

C)A spy embedded within an enemy government.

D)02 × 1023particles of a substance.

E)All of the above.

The correct answer, of course, is E. In chemistry, the mole (mol) is defined as an amount of a substance that contains 6.022 ×1023 particles of that substance. This number, called Avogadro’s number, is special because this number of particles has a mass in grams that is equal to the mass (in unified mass units) of a single particle of the substance.


How do scientists find the formula mass and molar mass of a substance?

  1. Calculate: The formula mass of a compound is the sum of the masses of each atom in the chemical formula. The unit of formula mass is the unified mass unit (u).Formula mass is also called molecular massif the compound is composed of molecules. Iron’s atomic mass is 55.85 u, carbon’s mass is 12.01 u, and oxygen’s mass is 16.00 u.


a. Calculate the formula mass of carbon monoxide (CO) by adding the atomic mass of carbon and the atomic mass of oxygen: __28.01__

b. Calculate the formula mass of carbon dioxide (CO2): __44.011__

c. Calculate the formula mass of iron (III) oxide (Fe2O3): __159.69__

  1. Infer: A mole of a substance has a mass in grams that is equal to the formula mass. For example, a carbon atom has an average mass of 12.01 u. A mole of carbon has a mass of 12.01 g. Based on their formula masses, list the molar mass of each substance. The unit for molar mass is g/mol, or grams per mole.



CO __28.01g/mol__

Fe __55.845g/mol__


Check your answers on the Gizmo by inspecting the middle row of tiles on the right side of the Gizmo. These tiles show the units “1 mol” on top and “g” below.

  1. Practice: Hydrogen has an atomic mass of 1.01 u. What is the molar mass of these substances?(Remember to use the units g/mol.)


H2O __18.02g/mol__





The students need to check if the equitation is still: Fe2O3+ 3CO →2Fe + 3CO2.


While solving problems in stoichiometry, it is useful to pay attention to the units of the answer. The process of comparing units is called dimensional analysis. A common technique involves using conversion factors to convert from one unit to another. Units that appear in the numerator and denominator of a fraction can be canceled out. For example, converting2 moles of carbon monoxide to grams involves multiplying by a conversion factor:

2 mol CO • 28.01 g CO= 56.02 g CO1 mol CO

All conversion factors are equivalent to one. For example, the conversion factor given above is equivalent to one because the numerator (28.01 g CO) and denominator (1 mol CO) represent the same amount of CO.The “molCO” unit is canceled, leaving an answer unit of grams.


Question: How do we solve problems in stoichiometry?

  1. Observe: The first question is: “How many moles of carbon monoxide (CO) are required to react completely with 1.75 moles of iron (III) oxide (Fe2O3)?” (If this is not the question you see, click New question until it appears.)


a. What unit is given in the question? ___Moles___

b. What quantity is asked for? ___Iron-oxide (Fe203)___

  1. Find: Look for the conversion factor that contains the units “mol Fe2O3” on top and “mol CO” on the bottom. Drag the tile containing this factor down to the green strip at the bottom.


According to the tile, how many moles of CO react with one mole of Fe2O3? __Mol__

  1. Analyze: To get an answer in moles of CO, you need to cancel the moles of Fe2O3. Turn on Show units.


a. What units are given to the right of the equals sign? __Mol CO___

b. If these aren’t the units you want, click Flip tile. What unit is given now? _Mol CO__

  1. Calculate: If the units are correct, multiply or divide the numbers to solve the problem.


a. How many moles of CO will react with 1.75 moles of Fe2O3? _5.25 mol CO__

b. Turn on Show numerical results. Were you correct? _Yes_

  1. Practice: Turn off Show units and Show numerical results. Click ‘New question’, and use what you’ve learned to solve another stoichiometry problem. For each problem, list the units given, the units asked for, and the solution.

The problems in the Gizmo are given in random order, so you may have to click Next question several times to see a new problem. (Note: Each term in the equation is either a solid (s), liquid (l), gas (g), or an aqueous solution (aq).)

If you are stuck, try one of the following hints:

  • If the given unit is grams (or liters or particles), convert from that unit to moles first. Then convert to moles of the answer substance.
  • If the answer unit is grams, liters, or particles, find the number of moles of the answer substance first. Then convert the moles of answer substance to the desired unit.
  • If you have a calculator, try to calculate the solution to each problem yourself before turning on the Show numerical solution check box.


A. What volume of carbon dioxide (CO2) will be produced if 2.90 moles of iron (Fe) is produced? (Note: In the Gizmo, it is assumed that all gases are at standard temperature and pressure, or STP.)
Given unit: __Mol Fe__ Answer unit: _Mol Co2__ Solution: __4.35 mol CO2_

B. What mass of iron (Fe) can be obtained from 3.80 g iron (III) oxide (Fe2O3) reacting with excess carbon monoxide (CO)?
Given unit: __9 Fe2O3__ Answer unit: __g Fe__ Solution: __2.66 g Fe__

C. How many moles of iron (Fe) will be produced from 6.20moles of carbon monoxide (CO) reacting with excess iron (III) oxide (Fe2O3)?
Given unit: _Mol CO__ Answer unit: __Mol Fe__ Solution: __0.20 Mol Fe__

D.How many molecules of carbon monoxide (CO) are needed to react with excess iron (III) oxide (Fe2O3) to produce 11.6 g of iron (Fe)?
Given unit: __9 Fe__ Answer unit: __Mole CO__ Solution: __8.73 Mol CO__

  1. On your own: Click New equation to try solving problems with a new chemical equation. It is known that there are five equations in all, and five problems per equation. Of course, the Gizmo will keep track of how many problems you solve.

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