key concepts

Question 1

the mole

Answer 1

amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon-12

Question 2

relative atomic mass

Answer 2

average mass of one atom of an element compared to one twelfth of the mass of one atom of carbon-12

Question 3

molar mass

Answer 3

mass in grams of 1 mole of a substance and is given the unit of g mol -1

Question 4

how can the molar mass of a compound be calculated?

Answer 4

adding up the mass numbers (from the periodic table) of each element in the compound

Question 5

calculate molesfor pure solids, liquids and gases

Answer 5

mass (g) / molar mass (mol)

Question 6

gas volume (dm3)

Answer 6

mole x 24

Question 7

concentration (mol dm-3)

Answer 7

mole / volume (dm3)

Question 8

cm3 - dm3

Answer 8

/1000

Question 9

cm3 - m3

Answer 9

/1 000 000

Question 10

dm3 - m3

Answer 10

/1000

Question 11

mg - g

Answer 11

/1000

Question 12

g - kg

Answer 12

/1000

Question 13

kg - tonnes

Answer 13

/1000

Question 14

hydrated salt

Answer 14

contains water of crystallisation
e.g. Cu(NO3)2.6H2O (hydrated copper (II) nitrate (V))
Cu(NO3)2 (anhydrous copper (II) nitrate (V))

Question 15

heating in a crucible

Answer 15

• weigh an empty, clean, dry crucible and lid
• add 2g of hydrated calcium sulfate to the crucible and weigh again
• heat strongly with a bunsen for a couple of minutes
• allow to cool, crucible needs to be dry otherwise wet crucible would give inaccurate result
• weigh the crucible again and contents again
• heat crucible again and reweigh until you reach a constant mass (do this to ensure reaction is complete)

Question 16

why should you put a lid?

Answer 16

improves accuracy of the experiment as it prevents loss of solid from the crucible but should be loose fitting to allow gas to escape