Identification Test

Question 1

CO3 2-

Answer 1

Add dilute acid, HNO3

• Effervescence

2H+(aq) + CO32-(aq) —— CO2(g) + H2O(l)

Question 2

Cl-

Answer 2

• AgNO3(aq)
• White precipitate
• Dissolves upon adding dilute aqueous ammonia
• Ag+(aq) + Cl-(aq) — AgCl(s)

Question 3

Cu2+

Answer 3

NaOH(aq):

• Dilute ~BLUE ppt
• Excess ~ DOES NOT dissolve
  Cu2+(aq) + 2OH-(aq) (reversible) Cu(OH)2(s)

Dilute NH3(aq) dropwise ~ BLUE ppt forms

Excess NH3(aq) ~ dissolves to form a deep blue solution [Cu(NH3)4(H2O)2]2+

Cu2+(aq) + 2OH-(aq) ———- Cu(OH)2(s)

Question 3

Br-

Answer 3

• AgNO3(aq)
• Cream ppt
• Dissolves in concentrated aqueous ammonia

Ag+(aq) + Br-(aq) — AgBr(s)

Question 4

I-

Answer 4

• AgNO3(aq)
• Yellow ppt
• DOESNT dissolves in concentrated ammonia
• Ag+(aq) + I-(aq) ———— AgI(s)

Question 5

SO4 2-

Answer 5

• Ba(NO3)2
• white ppt
• INSOLUBLE in dilute nitric acid
• Ba2+(aq) + SO42-(aq) ————- BaSO4(s)

Question 6

NH4+

Answer 6

• Add dilute NaOH(aq)
• warm and test gas with damp UI paper
• Turns BLUE in the presence of ammonia gas

NH4+(aq) + OH-(aq) (reversible) NH3(g) + H2O(l)

Question 7

Fe2+

Answer 7

• NaOH(aq)
• GREEN ppt forms

Fe2+(aq) + 2OH-(aq) — Fe(OH)2(s)

Question 8

Fe3+

Answer 8

• NaOH(aq)
• ORANGE-BROWN ppt

Fe3+(aq) + 3OH-(aq) —- Fe(OH)3(s)

Question 9

Mn2+

Answer 9

• NaOH(aq)
• LIGHT BROWN ppt

Mn2+(aq) + 2OH-(aq) ——– Mn(OH)2(s)

Question 10

Cr3+

Answer 10

Dilute NaOH(aq) ~GREEN-GREY ppt

Excess NaOH(aq) ~ ppt dissolves to form a GREEN solution

Cr3+(aq) + 3OH-(aq) —- Cr(OH)3(s)

Dilute NH3 dropwise ~ GREEN-GREY ppt

Excess NH3 ~ dissolves to form a PURPLE solution containing [Cr(NH3)6]3+

Cr3+(aq) + 3OH-(aq) ———- Cr(OH)3(s)