Subject: STEM
Grade: 10
Chapter 12.1
Name:
Date:
Stoichiometry: Reacting-mass calculations 1
1
Element
Ar
Element
Ar
Element
Ar
Aluminium (Al)
27
Hydrogen (H)
1
Phosphorus (P)
31
Bromine (Br)
80
Iodine (I)
127
Potassium (K)
39
Calcium (Ca)
40
Iron (Fe)
56
Silver (Ag)
108
Carbon (C)
12
Magnesium (Mg)
24
Sodium (Na)
23
Chlorine (Cl)
35.5
Nitrogen (N)
14
Sulfur (S)
32
Copper (Cu)
63.5
Oxygen (O)
16
Zinc (Zn)
65
Fluorine (F)
19
What mass of oxygen reacts with 192 g of magnesium? (3 marks)
2Mg + O2  2MgO
Step 1: Balance equation
2Mg + O2  2MgO
Step 2: Find Relative mass of each substance
related to the question
Mg = 24 x 2 = 48
Step 3: Find the Moles of the substance with
the mass (Moles = Mass ÷ Mr)
192g ÷ 24 = 8 moles magnesium
O2 = 16 x 2 = 32
Mole Ratio = 2:1
(because the equation is a 2:1 Ratio, oxygen
must have half the moles of magnesium,
therefore this = 4 Moles)
Step 4: Calculate mass of Oxygen (Mass =
Moles x Mr)
2
Mass = 4 x 32 = 128g
What mass of sulfur trioxide is formed from 96 g of sulfur dioxide? (3 marks)
2SO2 + O2  2SO3
Step 1: Balance equation
Step 2: Find Relative mass of each substance
related to the question
2SO2 + O2  2SO3
SO2 =
SO3 =
Step 3: Find the Moles of the substance with
the mass (Moles = Mass ÷ Mr)
Mole ratio:
Step 4: Calculate mass of sulfur trioxide.
(Mass = Moles x Mr)
Mass =
3
What mass of carbon monoxide is needed to react with 480 g of iron oxide? (3 marks)
Fe2O3 + 3CO  2Fe + 3CO2
Step 1: Balance equation
Fe2O3 + 3CO  2Fe + 3CO2
Step 2: Find Relative mass of each substance
related to the question
Step 3: Find the Moles of the substance with
the mass (Moles = Mass ÷ Mr)
Mole ratio:
Step 4: Calculate mass of carbon monoxide
Mass =
(Mass = Moles x Mr)
4
What mass of carbon dioxide is produced when 5.6 g of butene (C4H8) is burnt? (3 marks)
C4H8 + 6O2  4CO2 + 4H2O
Step 1: Balance equation
C4H8 + 6O2  4CO2 + 4H2O
Step 2: Find Relative mass of each substance
related to the question
Step 3: Find the Moles of the substance with
the mass (Moles = Mass ÷ Mr)
Mole ratio:
Step 4: Calculate mass of carbon dioxide
Mass =
(Mass = Moles x Mr)
5
What mass of oxygen is needed to react with 8.5 g of hydrogen sulfide (H2S)? (3 marks)
2H2S + 3O2  2SO2 + 2H2O
Step 1: Balance equation
2H2S + 3O2  2SO2 + 2H2O
Step 2: Find Relative mass of each substance
related to the question
Step 3: Find the Moles of the substance with
the mass (Moles = Mass ÷ Mr)
Mole ratio:
Step 4: Calculate mass of oxygen
(Mass = Moles x Mr)
Mass =
6. What mass of hydrogen is formed when 2 g of calcium reacts with hydrochloric acid? (1 mark)
Ca + 2HCl  CaCl2 + H2
Step 1: Balance equation
Ca + 2HCl  CaCl2 + H2
Step 2: Find Relative mass of each substance
related to the question
Step 3: Find the Moles of the substance with
the mass (Moles = Mass ÷ Mr)
Mole ratio:
Step 4: Calculate mass of hydrogen
Mass =
(Mass = Moles x Mr)
7What mass of carbon dioxide is made when 22 g of propane is burned in oxygen? (1 mark)
C3H8 + 5O2  3CO2 + 4H2O
Step 1: Balance equation
C3H8 + 5O2  3CO2 + 4H2O
Step 2: Find Relative mass of each substance
related to the question
Step 3: Find the Moles of the substance with
the mass (Moles = Mass ÷ Mr)
Mole ratio:
Step 4: Calculate mass of carbon dioxide
(Mass = Moles x Mr)
Mass =