# C5a: Moles and Molar Mass

What is the unit for the amount of a substance?
Mole
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What is the unit for molar mass?
g/mol
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What does the term Molar mass of a substance refer to?
It's relative formula mass in grams.
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What is conserved in a chemical reaction?
Mass
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What does number of moles =
Mass/Molar mass
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What is the relative atomic mass of an element defined as?
the average mass of an atom of the element compared to 1/12th the mass of an atom of carbon-12, 12C.
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What is the relative formula mass of water, H2O?
18
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What is the relative formula mass of calcium hydroxide, Ca(OH)2?
74
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Calcium carbonate decomposes to form calcium oxide and carbon dioxide when it is heated: Calcium Carbonate(50g) = Calcium Oxide (28g) + Carbon Dioxide (22g). What mass of carbon dioxide is made from 100 g of calcium carbonate?
44g
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When it is heated in air, magnesium reacts with oxygen to form magnesium oxide. Magnesium (48g) + Oxygen (32g) = Magnesium Oxide (80g). What mass of oxygen is needed to make 20 g of magnesium oxide?
8g
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What is the number of moles of carbon dioxide molecules in 22 g of CO2?
The relative formula mass Mr of carbon dioxide = 44. This means that the molar mass of carbon dioxide = 44 g/mol which means number of moles = 22 ÷ 44 = 0.5 mol
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What is the mass of 2 mol of carbon dioxide?
mass = number of moles × molar mass = 2 × 44 = 88 g
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10 mol of carbon dioxide has a mass of 440 g. What is the molar mass of carbon dioxide?
molar mass = mass ÷ number of moles = 440 ÷ 10 = 44 g/mol
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Sulfuric acid and sodium hydroxide react together to make sodium sulfate and water: H2SO4 + 2NaOH → Na2SO4 + 2H2O What mass of sodium sulfate is made when 20 g of sodium hydroxide reacts with excess sulfuric acid?
Molar mass of NaOH is 40 g/mol and molar mass of Na2SO4 is 142 g/mol. Number of moles of NaOH = 0.5mol, 0.5 mol of NaOH will react with 0.25 mol of Na2SO4. mass of Na2SO4 = 35.5g
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## Other cards in this set

### Card 2

#### Front

What is the unit for molar mass?

g/mol

### Card 3

#### Front

What does the term Molar mass of a substance refer to?

### Card 4

#### Front

What is conserved in a chemical reaction?

### Card 5

#### Front

What does number of moles =

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