Amount of Substance

Question 1

what is a mole?

Answer 1

the amount of a substance that contains as many particles of that substance as there are atoms in 12g of carbon-12

Question 2

what is avagadro’s number?

Answer 2

6.02 x10^-3

Question 3

what is the equation linking moles, mass and mr?

Answer 3

mass= mr x moles / moles= mass/mr

Question 4

what is molar mass?

Answer 4

the mass of one mole of a substance eg one mole of an oxygen molecule is 32 gmol ^ -1

Question 5

what is empirical formula?

Answer 5

the simplest whole number ratio of atoms in a compound

Question 6

in a hydrated salt, how do you find how many water molecules there are?

Answer 6

find the mass of the anhydrous salt and its mass after being heated, to find the mass of the water.
find the moles of both and put them into a ratio

Question 7

how do you calculate % uncertainty?

Answer 7

number of readings x equipment uncertainty
———————————————————– x 100
quantity

Question 8

if some hydrated solid spits out during the initial heating of the hydrated salt, how will this affect our value of x?

Answer 8

1) mass of water lost will be greater than it should
2) moles of water lost will be greater
3) x will be greater

Question 9

how to work out the moles in a gas at rtp?

Answer 9

moles = volume in dm3 / 24
moles = volume in cm3 / 24000

Question 10

what is the ideal gas equation?

Answer 10

pV= nRT
p= pressure (Pa)
V = volume (m3)
n = moles
R = gas constant- 8.314
T = temperature (K)

Question 11

how to work out the concentration in a solution?

Answer 11

concentration (moldm^-3) = moles/ volume (dm^3)

Question 12

how do you convert from moldm^-3 to gdm^-3?

Answer 12

multiply by the mr

Question 13

what is a standard solution?

Answer 13

a solution with a known concentration

Question 14

what is a titration?

Answer 14

an experimental technique used to correctly measure the volume of one solution that reacts exactly with another- it determines unknown concentrations