Math of Chemistry

Chemistry and Math Unit Review

Balancing Chemical Equations

The coefficients of a balanced chemical equation provide the mole ratio of reactants and products.

The goal when balancing an equation is to end up with an equal number of moles of atoms on each side of the arrow.

You may only change coefficents when balancing an equation!

Multiple Choice

Mole ratios are obtained from the

• balanced chemical equation

• periodic table

• molar mass

Multiple Choice

What is the mole ratio of H₂O to H₃PO₄ in the following chemical equation?  

P₄O₁₀ + 6 H₂O --> 4 H₃PO₄ 

• 6:4

• 4:6

• 1:3

• 3:1

Multiple Choice

For the Balanced Reaction: 3 Mg + 1 Fe₂O₃ → 3 MgO + 2 Fe

What is the Ratio of moles of MgO to moles Fe?

• 3mol Mg / 2 mol Fe

• 2 mol Mg/ 3 mol Fe

• 1 mol Fe/ 2 mol Fe

• 3 mol MgO / 2 mol Fe

Multiple Choice

When the following chemical equation is balanced, the coefficients will read :

CaC₂(s) + H₂O(l) --> C₂H₂(g) + Ca(OH)₂(aq)

• 1,2,2,2

• 1,2,1,1

• 2,1,1,1

• 2,1,2,1

Multiple Choice

What is the right ratio of chemicals for the BCE (Balanced Chemical Equation)?__H₂ + __S --> __H₂S

• 1,1 --> 1
• 2,2 --> 2
• 1,2 --> 1
• 1,2 --> 2

Multiple Choice

What is the right ratio of chemicals for the BCE (Balanced Chemical Equation)?__Al + __O₂--> __Al₂O₃

• 4,1 --> 2
• 4,3 --> 4
• 3,4 --> 1
• 4,3 --> 2

Multiple Choice

What is the right ratio of chemicals for the BCE (Balanced Chemical Equation)?__AgNO₃ + __H₂S --> __Ag₂S+ __HNO₃

• 2,1 --> 1,2
• 1,2 --> 1,1
• 1,2 --> 1,2
• 1,2 --> 2,1

Multiple Choice

What is the right ratio of chemicals for the BCE (Balanced Chemical Equation)?__CO + __Fe₂O₃--> __Fe + __CO₂

• 3,1 --> 2,3
• 3,2 --> 1,1
• 3,2 --> 2,4
• 3,2 --> 2,1

Multiple Choice

How many grams are in 7.8 moles of NaCl?

Hint: You may want to consult your Chemistry Reference Tables!

• 476grams

• 460 grams

• 452 grams

• 462 grams

Mole to Mole Stoichiometry (Change the recipe!) Problems

Set up a proportion by writing the original recipe on the bottom and the new recipe on the top of the balanced equation! Solve for the unknown!

Multiple Choice

Given the reaction: 4Al + 3O₂ --> 2Al₂O₃

How many moles of Aluminum oxide, Al₂O₃, can you produce if you have 2 moles of Al?

• 3 mole

• 2 mole

• 1 mole

• 0.5 mole

Multiple Choice

N₂ +  3H₂ → 2NH₃ 
How many moles of hydrogen are needed to react with 2 moles of nitrogen?

• 6
• 2
• 3
• 1

Multiple Choice

Using the following equation:
Fe₂O₃(s) + 3H₂(g) → 2Fe(s) + 3H₂O(l)
How many moles of iron can be made from  6 moles H₂? 

• 4 moles Fe
• 6 moles Fe
• 9 moles Fe
• 2 moles Fe

Multiple Choice

6CO₂ + 6H₂O --> C₆H₁₂O₆ + 6O₂ 
What is the total number of moles of water needed to make 2.5 moles of C₆H₁₂O₆?

• 2.5
• 6
• 12
• 15

Multiple Choice

4NH₃ + 5O₂-->4NO + 6H₂O
What is the total number of moles of H₂O produced when 12 mole of NH₃ is completely consumed?

• 15
• 18
• 20
• 24

Multiple Choice

Which of the following represent a mole ratio between silver nitrate and copper(II) nitrate in the following reaction:

2AgNO₃ + Cu --> Cu(NO₃)₂ + 2Ag

• 2 mol AgNO₃ / 2 mol Ag

• 2 mol Ag / 2 mol AgNO₃

• 2 mol AgNO₃ / 2 mol Cu(NO₃)₂

• 2 mol AgNO₃ / 1 mol Cu(NO₃)₂

Types of Chemical Reactions

Be sure that you can classify chemical reactions!

Multiple Choice

What kind of reaction is this:
Fe + CuSO₄ -> Cu + FeSO₄

• Double Replacement
• Decompostion
• Single Replacement
• Combustion

Multiple Choice

The blue numbers in the image below represent ________

• I don't know, and don't want to try
• coefficients
• subscripts
• none of the answers are correct

Multiple Choice

The red numbers in the image below represent ________

• subscripts
• coefficients
• I don't know, and don't want to try
• None of the answers are correct

Multiple Choice

Classify the reaction:

3KOH + H₃PO₄ --> K₃PO₄ + 3H₂O

• Combination

• Decomposition

• Single replacement

• Double replacement

Multiple Choice

What type of chemical reaction is this one?

Ca + MgCl2 --> CaCl2 + Mg

• Decomposition

• Combustion

• Synthesis

• Single Replacement

Multiple Choice

What type of chemical reaction is this one?

Al(OH)₃ --> Al2O3 + H2O

• Decomposition

• Combustion

• Synthesis

• Single Replacement

Multiple Choice

What are the products of the chemical reaction pictured?

• CH₄ and CO₂

• CH₄ and O₂

• CO₂ and H₂O

• O₂ and H₂O

Multiple Choice

What are the reactants in the chemical equation pictured?

• CH₄ and CO₂

• CH₄ and O₂

• CO₂ and H₂O

• O₂ and H₂O

Multiple Choice

What type of reaction involves ions from 2 compounds exchanging places to form 2 completely new compounds?

• Single Replacement Reaction

• Double Replacement Reaction

• Synthesis Reaction

• Decomposition Reaction

Multiple Choice

What type of reaction involves one element replacing another element in a compound?

• Single Replacement Reaction

• Double Replacement Reaction

• Synthesis Reaction

• Decomposition Reaction

Multiple Choice

What type of reaction involves 2 substances combining to form 1 new compound?

• Decomposition Reaction

• Single Replacement Reaction

• Double Replacement Reaction

• Synthesis Reaction

Multiple Choice

What type of reaction involves the breaking down of a substance into simpler substances?

• Single Replacement Reaction

• Double Replacement Reaction

• Synthesis Reaction

• Decomposition Reaction

Other topics . . .

Be sure you are familiar with the other topics in this unit that we have covered previously!

Multiple Choice

How many grams are in 0.523 mol of AlPO₄?

• 63.78 g

• 38.68 g

• 47.23 g

• 55.43 g

Multiple Choice

A can of Coke has 39g of sugar. The formula for table sugar is C₁₂H₂₂O₁₁. How many moles of sugar is in a can of Coke?

• 0.414 mol

• 0.314 mol

• 0.214 mol

• 0.114 mol

Multiple Choice

How many grams are in 0.375 mol KBr

• 39,10 g

• 44.625 g

• 0.003 g

• 56.525 g

Multiple Choice

How many moles are in 98.3 g of Aluminum Hydroxide (Al(OH)₃)?

• 78.0 mol

• 1.30 mol

• 6.60 mol

• 5.90 mol

Multiple Choice

How many moles are in 1459 grams of Na?

• 63.46 moles

• 60.36 moles

• 10 moles

• 1 mole

Multiple Choice

How many moles are in 19.82 g Mg? 

• 1.226mol Mg
• 481.7mol Mg
• 1.000mol Mg
•  0.8156 mol Mg

Multiple Choice

How many moles are in 16.94g of water?

• 16.94 mol H₂O
• 0.9401 mol H₂O
• 305.3 mol H₂O
• 1.063 mol H₂O

Multiple Choice

A 15.67 g sample of a hydrate of magnesium carbonate was heated to drive off the water. The mass was reduced to 7.58 g. What is the percent of the water in the hydrate?

• 51.6%

• 48.4%

• 93.7%

• 100%

Multiple Choice

A hydrate of magnesium chloride is present and the following data is collected:

mass of crucible = 22.130 grams

mass of crucible + hydrate = 25.290 grams

mass of crucible and contents after heating = 23.491 grams

What is the percent water in this hydrate?

• 7.1135%

• 100.00%

• 56.930%

• 7.6583%

Multiple Choice

An empirical formula:

• is a formula that calculates the coefficients of a compound in a balanced equation.
• is the simplest whole-number ratio of moles of elements in the compound.

Multiple Choice

A compound is a hydrate when it...

• is composed of only hydrogen and oxygen
• is a state of water
• traps water inside of the compound
• repels water from the compound

Multiple Choice

Which element in the compound potassium cyanide, KCN, has a percent composition of 60.97%?

• K

• C

• N

• None of the above

Multiple Choice

What is the percent composition of Benzene, C₆H₆?

• C = 50%
  H = 50%
• C = 85.7 %
  H = 14.3%
• C = 92.2%
  H = 7.8%
• C = 71.9%
  H = 28.1%

Multiple Choice

What is the empirical formula for the following:
Pb₅Cr₅O₂₀

• Pb₂Cr₂O₁₀
• PbCr₂O₇
• Pb₉Cr₄O₂
• PbCrO₄

Multiple Choice

What is the percent composition by mass of sulfur in the compound MgSO₄ (gram formula mass = 120 g/mol)?

• 20%
• 27%
• 46%
• 53%

Multiple Choice

What is the percent by mass of fluorine in CaF₂ (gram-formula mass = 78 g/mol)?

• 24%
• 49%
• 51%
• 65%

Multiple Choice

What is the molar mass of C₂H₄O₂?

• 40g
• 50g
• 60g
• 68g

Multiple Choice

What is the formula (molar) mass of AuCl₃?

• 96 g/mol

• 130 g/mol

• 232.5 g/mol

• 303.5 g/mol

Multiple Choice

How many atoms are there TOTAL in:
H₂SO₄

• 6
• 5
• 7
• 3

Multiple Choice

What is the molar mass of one molecule of Nitrogen N₂?

• 14.01 amu
• 14.01 g
• 28.02 g
• 28.02 amu

Multiple Choice

What is the Molar mass of one mole of Iron (Fe)?

• 55.93 amu
• 55.93 g
• 111.86 amu
• 111.86 g

Multiple Choice

What is the gram formula mass for Mg(OH)₂?

• 41.3g

• 58.32g

• 65.6g

Multiple Choice

How many atoms of Oxygen are in Fe(NO₃)₃ ?

• 6
• 3
• 9
• 1

Multiple Choice

How many Nitrogen atoms are in (NH₄)₂CrO₄?

• 1

• 2

• 8

• 16

Multiple Choice

C₃H₅(NO₃)₃

• C = 3, H = 5, N = 3, O = 9

• C = 3, H = 5, N = 1, O = 9

• C = 9, H = 15, N = 3, O = 9

• C = 9, H = 15, N = 1, O = 3

Multiple Choice

4CF₂Cl₂

• C = 4, F = 4, Cl = 2

• C = 1, F = 8, Cl = 8

• C = 4, F = 8, Cl = 8

• C = 1, F = 4, Cl = 8

Multiple Choice

How many different elements are present in H₂COCH₂

• 5

• 4

• 3

• 2

Multiple Choice

Find the mass of 11.37 mol of BaO. Round to the nearest whole number.

• 1,354 g

• 1,740 g

• 17.40 g

• 1,684 g