Reactions of the Group 2 Oxides and Hydroxides, and Trends in Solubility Flashcards
what are the group 2 oxides classified as and what does it mean
- basic oxides
- meaning they can react with water to form alkalis
what observation is made when a group 2 oxide reacts with water
the solids react to form colourless solutions
what is the general equation for the reaction between a group 2 oxide and water using M
MO(s) + H2O(l) = M(OH)2(aq)
what is the ionic equation for these reactions and what do they tell us (you can split the oxide into its ions to show this)
- M2 + + O2- + H2O = M2+ + 2OH- (cancel M2+ spectator)
- O2+ + H2O = 2OH-
- the product is hydroxide ions, which is what makes them alkaline
what is the trend in the solubility of the group 2 hydroxides down the group
their solubility increases down the group
what does this therefore mean about the trend in heir pH down the group
it also increases
what is the limewater in the carbon dioxide test
saturated aqueous solution of calcium hydroxide
what is the equation for the reaction between limewater and CO2
CO2(g) + Ca(OH)2(aq) = CaCO3(s) + H2O(l)
why is magnesium hydroxide often used to relieve symptoms of indigestion
- because its an alkali
- indigestion is often caused by too much HCl in the stomach
- so by taking in Mg(OH)2 it neutralises some of the acid to relieve symptoms
what is the equation for the reaction between magnesium hydroxide and hydrochloric acid
Mg(OH)2 + 2HCl = MgCl2 + 2H2O
what do all group 2 oxides and hydroxides react with acids to form
salt and water
what observations are made from all of these reactions
a white solid reacting to form a colourless solution
how lime (calcium hydroxide) used in agriculture
- farmers use it to control soil acidity
- so a greater yield of crops can be obtained
are all group 2 nitrates and chlorides soluble
yes
what is the trend in the solubility of group 2 sulfates down the group
their solubility decreases
therefore why are barium ions used in the test for sulfate ions in solution
- because when barium and sulfate ions react to form barium sulfate
- it would form a white precipitate as it is barely soluble
what is the ionic equation for this reaction
Br2+(aq) + SO4^2-(aq) = BrSO4(s)
as there are other anions that could form a white precipitate with barium ions, what needs to be added into the solution in order to stop this and how will it do this
- a dilute acid like HCl or HNO3
- these would bring H+ ions into the equation
- this would prevent barium carbonate from forming as a white precipitate
- as the CO3^2- ions would react with the H+ ions to form hydrocarbonate ions (HCO3-)
why is barium sulfate used in hospitals for people
- the barium sulfate is put into a meal forming a barium meal
- the BrSO4 allows soft tissues to show up in x-rays clearly for examination
- as its a dense white solid
despite barium ions being poisonous, why is barium sulfate used for people
- because barium sulfate is insoluble
- so the ions arent free to move and poison
