3.1.2 group 2

Question 1

state and explain the trend of atomic radii in group 2 elements

Answer 1

increase
•more shells
•more shielding
•atom becomes bigger

Question 2

state and explain the trend of first ionisation energy in group 2 elements

Answer 2

decrease
• more shells
• more shielding
• less attraction of outer electrons to nucleus to electrons are lost more easily

Question 3

state and explain the trend of reactivity in group 2 elements

Answer 3

increase
•atom radii increases as there are more shells and more shielding
•nuclear attraction decreases
•outer electrons are more easily lost

Question 4

state and explain the trend of melting points in group 2 elements

Answer 4

overall decrease
•metallic bonding weakens as atomic size decreases (due to more shells and more shielding)
•distance between +ions and free e- increase to electrostatic force of attraction between them decreases

Question 5

describe MgO

Answer 5

white solid with high mp due to ionic bonds

Question 6

how can a the layer of MgO be cleaned off of Mg ribbon

Answer 6

using emery paper

Question 7

how would unclean Mg ribbon affect a reaction

Answer 7

give a false result because Mg and MgO react at different rates

Question 8

give the equation and observation of Mg burning in steam

Answer 8

Mg(s) + H2O(g) —> MgO(s) + H2(g)

•bright white flame

Question 9

give the equation and observation of Mg reacting with warm water

Answer 9

Mg(s) + 2H2O —> Mg(OH)2(aq) + H2(g)
•fizzing
•metal dissolves 
•white ppt
•slow reaction

Question 10

give the basic equation and observation of group 2 metals in other than Mg in cold water

Answer 10

metal(s) + 2H2O —> metal(OH)2(aq) + H2(g)
•fizzing
•metal dissolves
•reaction becomes more vigorous down the group
•ca forms white ppt others form colourless solution

Question 11

give the basic equation for a group 2 metal with an acid

Answer 11

metal + acid —> salt + hydrogen

Question 12

why is the reaction slow when barium is reacted with sulphuric acid

Answer 12

insoluble barium sulphate is formed that covers the surface of the metal acting as a barrier to further reaction

Question 13

give the basic reaction of group2 oxides with water

Answer 13

metal oxide (s) + h2o(l)—> metal hydroxide (?)

Question 14

why does mg(oh)2 have a pH of 9

Answer 14

only slightly soluble in water so fewer free OH- ions are produced

Question 15

what is mg(oh)2 used for in medicine and give an equation

Answer 15

neutralise excess stomach

Mg(OH)2(s) + 2HCl —> MgCl2(aq) + 2H2O(l)

Question 16

what is the pH and solubility of ca(oh)2

Answer 16

12 fairly soluble

Question 17

what is calcium hydroxide used for and what is the drawback of this use

Answer 17

in agriculture to neutralise acidic soils

if too much is added soils could become too alkaline to sustain crop growth

Question 18

what can aqueous calcium hydroxide be used for and give a reaction

Answer 18

also called as limewater that can be used to rest for carbon dioxide as limewater turns cloudy when calcium carbonate is produced
Ca(OH)2(aq) + CO2(g) —> CaCO3(s) +H2O(l)

Question 19

what can barium sulphate be used for

Answer 19

it is toxic and can be given to patients to x-ray their intestines in the form of a barium meal