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Unit 9 Stoicheometry

Total questions: 79

Worksheet time: 45mins

Name
Class
Date
1.

How many moles are in 36.0 g of water (H₂O)?

(a)  

2.
Which of the following represents a mole ratio from the equation: 2H₂ + O₂ → 2H₂O?
a)
2 mol H₂ : 2 mol H₂O
b)
1 mol H₂ : 1 mol O₂
c)
2 mol O₂ : 2 mol H₂
d)
2 mol H₂O : 1 mol H₂
e)
1 mol H₂O : 2 mol O₂
3.
Which unit is commonly used to express molar mass?
a)
g/mL
b)
g/mol
c)
mol/L
d)
mol/m³
e)
atoms/mol
4.

You have 6.02 × 10²³ molecules of CO₂. How many moles is this?

(a)  

5.
From the equation: N₂ + 3H₂ → 2NH₃, what is the mole ratio of H₂ to NH₃?
a)
1:1
b)
3:2
c)
2:3
d)
3:1
e)
2:1
6.
Select all correct mole-to-mass conversions.
a)
2 mol Na = 46.0 g Na
b)
1 mol H₂O = 18.0 g
c)
0.5 mol CO₂ = 22.0 g
d)
3 mol O₂ = 96.0 g
e)
1 mol C = 6.02 × 10²³ g
7.

Challenge: How many molecules are in 36.0 g of water (H₂O)?

(a)  

8.
What step comes first in a stoichiometry problem?
a)
Convert to moles
b)
Check sig figs
c)
Write and balance the chemical equation
d)
Calculate percent yield
e)
Convert to desired unit
9.

Challenge: If 4.0 mol H₂ reacts completely with excess O₂, how many grams of H₂O are produced?

(a)  

10.
Why do you need a balanced equation before doing mole ratio calculations?
a)
It shows the limiting reactant
b)
It ensures unit cancellation
c)
It confirms Avogadro’s number
d)
It provides correct mole relationships
e)
It allows molarity calculations
11.

In the reaction 2Al + 3Cl₂ → 2AlCl₃, how many grams of AlCl₃ are produced from 4.5 g of Al?

(a)  

12.
What is the purpose of mole ratios in stoichiometry problems?
a)
To find molar mass
b)
To relate different compounds in a reaction
c)
To measure concentration
d)
To find the volume of gases
e)
To determine density
13.
What quantity is always conserved in a balanced chemical equation?
a)
Moles
b)
Mass
c)
Volume
d)
Number of molecules
e)
Density
14.

From: Fe₂O₃ + 3CO → 2Fe + 3CO₂, how many grams of Fe can be produced from 159.6 g of Fe₂O₃?

(a)  

15.

Challenge: If 10.0 g of Ca reacts with water, how many grams of H₂ gas are produced?

(a)  

16.
Which conversion is needed for a mass-mass stoichiometry problem?
a)
grams → mol → mol → grams
b)
mol → L → mol
c)
g → L
d)
mol → grams
e)
mol → atoms
17.
What must be done before using a chemical equation for stoichiometry?
a)
Check lab data
b)
Convert everything to grams
c)
Balance the equation
d)
Cancel units
e)
Draw particle diagrams
18.

Challenge: You have 15.0 g of HCl and excess NaOH. How many grams of NaCl will be formed?

(a)  

19.
Select all true statements about balanced equations and mole ratios.
a)
They show proportions of compounds
b)
They are used to compare masses directly
c)
They are the core of stoichiometry
d)
They allow predicting product amount
e)
They are optional in calculations
20.
Which formula helps convert grams to moles in stoichiometry?
a)
mass × volume
b)
mol = mass / molar mass
c)
moles × Avogadro’s number
d)
PV = nRT
e)
density = mass / volume
21.

What volume of hydrogen gas is produced at STP when 2.00 mol of H₂ forms?

(a)  

22.
Which equation is used for gas-volume conversions at STP?
a)
PV = nRT
b)
V = m/d
c)
1 mol = 22.4 L
d)
mass = mol × MM
e)
V = IR
23.

How many liters of CO₂ are formed when 8.00 g CH₄ reacts completely with O₂?

(a)  

24.

What is the balanced equation for: methane + oxygen → carbon dioxide + water?

(a)  

25.

Challenge: What volume of O₂ at STP is needed to completely burn 3.00 mol of propane (C₃H₈)?

(a)  

26.
What gas law equation is used when not at STP?
a)
PV = nRT
b)
1 mol = 22.4 L
c)
mass = density × volume
d)
P₁V₁ = P₂V₂
e)
E = mc²
27.

From the reaction: Zn + 2HCl → ZnCl₂ + H₂, how many liters of H₂ gas at STP from 13.0 g Zn?

(a)  

28.
What condition defines STP for gas calculations?
a)
1 atm & 0°C
b)
25°C & 1 atm
c)
0 K & 1 atm
d)
273°C & 1 atm
e)
273 K & 2 atm
29.
Why is 22.4 L/mol valid only under certain conditions?
a)
It applies only to solids
b)
It depends on ideal behavior at STP
c)
It applies only to CO₂
d)
It depends on molar mass
e)
It is used for liquids
30.
Select all that apply: Which reactions produce a gaseous product?
a)
Combustion of CH₄
b)
Decomposition of H₂O₂
c)
Neutralization of HCl and NaOH
d)
Zn + HCl
e)
Precipitation of AgCl
31.

What is the limiting reactant in a reaction with 5.0 g of H₂ and 20.0 g of O₂?

(a)  

32.
Which step is necessary to identify the limiting reactant?
a)
Identify excess mass
b)
Balance the equation
c)
Assume 1 mol of each reactant
d)
Guess the smallest mass
e)
Convert both to the same product
33.
From: N₂ + 3H₂ → 2NH₃, if 1.0 mol N₂ reacts with 3.0 mol H₂, what is the limiting reactant?
a)
N₂
b)
H₂
c)
NH₃
d)
Equal amounts
e)
O₂
34.
What does the limiting reactant determine?
a)
Which product forms
b)
The total product mass
c)
Which gas escapes
d)
Color of the reaction
e)
The reaction rate
35.

Challenge: You mix 10.0 g of Al with 15.0 g of Cl₂. Which is the limiting reactant?

(a)  

36.
To determine the limiting reactant, you should:
a)
Only convert grams to moles
b)
Use the smaller mass
c)
Convert both to moles of a product
d)
Guess using periodic table
e)
Only balance the equation
37.
Which of these is NOT a correct statement about limiting reactants?
a)
They determine how much product forms
b)
They are always in excess
c)
They are completely consumed
d)
They must be identified to solve for mass
e)
They control percent yield
38.
Select all steps used to find the limiting reactant.
a)
Balance the equation
b)
Convert each reactant to mol
c)
Compare mole ratio to product
d)
Use smallest molar mass
e)
Choose reactant with least moles of product
39.

You calculated 20.0 g of product, but only obtained 15.0 g. What is the percent yield?

(a)  

40.
What does a 100% yield mean?
a)
Reactants are recycled
b)
No product is made
c)
All predicted product was formed
d)
Excess reactant remains
e)
Limiting reactant is unused
41.

Challenge: You obtain 5.6 g of product from a reaction expecting 7.0 g. What is the percent yield?

(a)  

42.
Why might actual yield be less than theoretical?
a)
Incorrect molar mass
b)
Measurement inaccuracy
c)
All product was used
d)
Too much limiting reactant
e)
Perfect reaction setup
43.
Which of the following is an actual use of stoichiometry in industry?
a)
Designing lab notebooks
b)
Calculating wages
c)
Predicting product yield
d)
Estimating weather
e)
Coloring materials
44.

If 5.00 g of CaCO₃ decomposes completely, how many liters of CO₂ gas form at STP?

(a)  

45.

Challenge: If 50.0 g of ethanol combusts, how many grams of CO₂ are produced?

(a)  

46.

Multi-step: What mass of water is produced when 10.0 g of H₂ reacts with excess O₂?

(a)  

47.

Challenge: A rocket produces 24.0 g of H₂O from fuel. How much O₂ was consumed?

(a)  

48.
Which of the following correctly orders the stoichiometry steps?
a)
Convert → Balance → Ratio → Solve
b)
Guess → Calculate → Measure
c)
Balance → Convert to mol → Mole ratio → Convert units
d)
React → Record → Solve
e)
Molar mass → PV = nRT → Final
49.
What error is made if you forget to convert grams to moles first?
a)
Too much product predicted
b)
Cannot compare ratios correctly
c)
Mass is lost
d)
Balanced equation becomes incorrect
e)
Volume changes at STP
50.
What step is most often skipped when students miss a stoichiometry problem?
a)
Sig fig check
b)
Balancing the equation
c)
Labeling the answer
d)
Writing a conclusion
e)
Estimating mass
51.
Which unit conversions are necessary for a volume-mass stoichiometry problem?
a)
Volume to moles (at STP)
b)
Grams to moles
c)
Moles to volume
d)
Atoms to moles
e)
Liters to grams
52.
Why is it incorrect to compare grams of two substances directly?
a)
They are always equal
b)
Their molar masses are different
c)
One is lighter
d)
Avogadro's number is irrelevant
e)
They have different shapes
53.

Challenge: Identify the mole ratio error in: 2Na + Cl₂ → 2NaCl → used 1:2 instead of 2:1

(a)  

54.

What is the molar mass of calcium hydroxide, Ca(OH)₂?

(a)  

55.
In a combustion reaction, what are the two main products?
a)
H₂ and O₂
b)
H₂O and CO₂
c)
O₂ and heat
d)
C and ash
e)
C₂H₆ and light
56.

How many particles are in 2.00 mol of any substance?

(a)  

57.

From: 2Mg + O₂ → 2MgO, how many moles of O₂ are needed for 4.00 mol of Mg?

(a)  

58.

A gas occupies 44.8 L at STP. How many moles of gas are present?

(a)  

59.
Select all valid mole-to-mole conversions from balanced reactions.
a)
2Na → 2NaCl
b)
2H₂ + O₂ → 2H₂O → 2 mol O₂ : 1 mol H₂O
c)
1 mol Ca + 2 mol HCl → 1 mol H₂
d)
3H₂ + N₂ → 2NH₃
e)
CH₄ + 2O₂ → CO₂ + 2H₂O
60.

What is the percent yield if theoretical yield is 80 g and actual yield is 72 g?

(a)  

61.

If you need 3.00 mol of H₂O, how many mol of O₂ do you need from: 2H₂ + O₂ → 2H₂O?

(a)  

62.

Rocket fuel produces 180 g of H₂O. How many moles of water is this?

(a)  

63.

How many grams of NaCl are formed from 5.0 g of Na reacting with excess Cl₂?

(a)  

64.

In a lab, 4.50 g of product was expected, but 4.20 g was obtained. What is percent yield?

(a)  

65.

Burning 8.0 g of CH₄ produces how many grams of CO₂? (CH₄ + 2O₂ → CO₂ + 2H₂O)

(a)  

66.
Why is stoichiometry important in manufacturing?
a)
To make pretty labels
b)
To predict yields and reduce waste
c)
To weigh machines
d)
To measure air pressure
e)
To generate electricity
67.

How many grams of H₂ are in 11.2 L of gas at STP?

(a)  

68.

Challenge: What is the mass of 2.00 mol of SO₂ gas?

(a)  

69.

You have 0.750 mol of N₂ gas. What volume at STP?

(a)  

70.

What is the molar mass of Na₂CO₃?

(a)  

71.

A student used 50 g of reactant but got only 30 g of product. What is the percent yield?

(a)  

72.
Select all correct conversions that use mole relationships.
a)
mol to mol
b)
mol to grams
c)
mol to particles
d)
mol to liters (at STP)
e)
grams to liters (directly)
73.
Which of the following is the correct setup for a mass-volume problem?
a)
mass → mol → mol → volume
b)
volume → mol → mol → mass
c)
volume → grams → mol
d)
mass → volume → mol
e)
mass → atoms → mol
74.

A chemical yields 5.0 mol of gas. What is the volume at STP?

(a)  

75.
Which of the following is true about limiting reactants?
a)
They are never completely used
b)
They produce the most product
c)
They determine maximum product formed
d)
They can be ignored in gas reactions
e)
They have smallest molar mass
76.

From: 2H₂ + O₂ → 2H₂O. If 4 mol H₂ react, how many mol H₂O form?

(a)  

77.

Combustion of 6.0 g C produces how much CO₂?

(a)  

78.

What is Avogadro’s number?

(a)  

79.

A solution has 2.5 mol of solute in 1.0 L. What is the molarity?

(a)  

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