quantitative chemistry

Question 1

what is molar mass?

Answer 1

the mass in grams of one mole of a substance

Question 2

what is a mole:

Answer 2

how much of a substance contains 6.02x10^23 particles
one mole of any substance contains same number of units as other substances

Question 3

The link between the mole and the relative atomic mass of an element is:

Answer 3

The numerical value of the relative atomic mass of any element;
Is equal to the mass of one mole of that element;
In grams;

Question 4

formula for sodium carbonate

Answer 4

Na2CO3

Question 5

Avogadro’s Law

Answer 5

states that at the same conditions of temperature and pressure, equal amounts of gases occupy the same volume of space

Question 6

how to work out moles

Answer 6

mass/Mr

Question 7

how to work out volume of gas in cm3

Answer 7

volume (cm3) = moles x 24, 000 (cm3/mol)

Question 8

how to work out volume of gas in dm3

Answer 8

volume (dm3) = moles x 24 (dm3/mol)

Question 9

Explain why the mole is used as a value

Answer 9

The mass of each individual atom is so small that it becomes insignificant. (1)
Therefore, the mole is used to account for a larger number of atoms that can be measured. (1)
This also allows direct comparison of elements to calculate the mass of individual atoms. (1)

Question 10

write a balanced equation of magnesium reacting with hydrochloric acid

Answer 10

Mg + 2HCl -> MgCl2 + H2

Question 11

what is avogadros constant

Answer 11

num. of moles, molecules or ions in a mole of a given substance
value of the constant is 6.02 x 10 ^ 23

Question 12

What mass of chlorine reacts with 32.4 g of aluminium?
2Al + 3Cl₂ ➔ 2AlCl₃

Answer 12

1) find the moles of aluminium:
moles = mass / Mr
32.4 / 27 = 1.2

2) find the moles of chlorine using molar ratio
2:3 ➔ (1.2/2) x 3 = 1.8

3) find mass of chlorine
mass = moles x Mr
1.8 x (35.5 x 2) = 127.8

➔ 127.8 g of chlorine