REQUIRED PRACTICALS

Question 1

• describe the test for sulfate ions
• what would a positive result be

Answer 1

1. Add HCl to unknown sample (aq) to remove any carbonate ions
2. Add BaCl2
   - white precipitate of Barium Sulfate, BaSO4 (s)

Question 2

Why must the solution first be acidified (addition of HCl) when testing for sulfate ions

Answer 2

• to remove any carbonate ions
• avoids BaCL2 from forming a white ppt and showing a false positive

Question 3

• state the ionic equations for the Group 2 hydroxides that would form precipitates
• why

Answer 3

• Mg2+ (aq) + 2OH- (aq) ➡️ Mg(OH)2 (s)
• Ca2+ (aq) + 2OH- (aq) ➡️ Ca(OH)2 (s)
• they are only slightly soluble, so do not dissolve as much as the others

Question 4

• state the ionic equations for the Group 2 sulfates that form precipitates
• why

Answer 4

• Ca2+ (aq) + SO4 2- (aq) ➡️ CaSO4 (s)
• Sr2+ (aq) + SO4 2- (aq) ➡️ SrSO4 (s)
• Ba2+ (aq) + SO4 2- (aq) ➡️ BaSO4 (s)
• they are insoluble, so do not dissolve in the solution