What a mole actually is, the Avogadro constant, converting between mass and moles, and using moles to balance an equation. Higher tier content.
You can study this deck without signing up — your progress is kept in this browser. An account saves it properly, syncs it across devices, and lets you edit the cards.
1.What is the unit for amount of substance?
The mole, symbol mol.
2.What is the Avogadro constant?
6.02 x 10 to the power 23, the number of atoms, molecules or ions in one mole of a substance.
3.What is the mass of one mole of a substance?
Its relative formula mass in grams.
4.What is the mass of one mole of water, Mr 18?
18 g.
5.State the equation linking mass, moles and Mr.
moles = mass in grams divided by relative formula mass.
6.Rearrange to find mass.
mass = moles x Mr
7.Rearrange to find Mr.
Mr = mass divided by moles
8.How many moles are in 36 g of water, Mr 18?
36 divided by 18 = 2 moles.
9.How many moles are in 11 g of carbon dioxide, Mr 44?
11 divided by 44 = 0.25 moles.
10.What is the mass of 0.5 moles of calcium carbonate, Mr 100?
0.5 x 100 = 50 g.
11.What is the mass of 3 moles of magnesium oxide, Mr 40?
3 x 40 = 120 g.
12.How many particles are in 2 moles of a substance?
2 x 6.02 x 10 to the power 23, which is 1.204 x 10 to the power 24.
13.How many atoms are in one mole of carbon?
6.02 x 10 to the power 23 atoms.
14.Why do equal numbers of moles of different substances have different masses?
They contain the same number of particles, but the particles themselves have different masses.
15.What do the big numbers in a balanced equation tell you?
The ratio in which the substances react, measured in moles.
16.In 2Mg + O2 gives 2MgO, what is the mole ratio?
2 moles of magnesium react with 1 mole of oxygen to give 2 moles of magnesium oxide.
17.How can masses be used to work out a balanced equation?
Convert each mass into moles, then divide all the values by the smallest to get the simplest whole number ratio.
18.48 g of magnesium reacts with 32 g of oxygen. Find the mole ratio. Mg is 24, O2 is 32.
Magnesium: 48 divided by 24 = 2 moles. Oxygen: 32 divided by 32 = 1 mole. The ratio is 2 to 1.
19.Why is the mole such a useful idea?
It links a number of particles, which cannot be counted, to a mass, which can be measured on a balance.
20.How many moles are in 4 g of hydrogen gas, H2, Mr 2?
4 divided by 2 = 2 moles.
21.What is the mass of 0.1 moles of sodium chloride, Mr 58.5?
0.1 x 58.5 = 5.85 g.
22.Why must you use Mr and not Ar for a compound?
Ar applies to a single atom of an element. A compound contains several atoms, so you need the sum of them all.
23.One mole of oxygen gas is O2. What is its mass? O is 16.
32 g, because the molecule contains two oxygen atoms.
24.A student says one mole of oxygen weighs 16 g. What have they got wrong?
They used the relative atomic mass of a single oxygen atom. Oxygen gas exists as O2 molecules, so one mole has a mass of 32 g.
25.Convert 0.25 moles of CaCO3 into a mass. Mr is 100.
0.25 x 100 = 25 g.
26.How many moles is 5.85 g of NaCl, Mr 58.5?
5.85 divided by 58.5 = 0.1 moles.
You remember far more by trying to recall an answer than by reading it. Run these as flashcards and the ones you keep getting wrong will come back more often.
Start studyingOr see the other Quantitative Chemistry decks.