Official ID Tests for the Group 1A Cations

Name of Test Reagents Confirmatory Test

Chemical Equations Visible Results Principle Involved

I. Li+

1-1 Lithium Carbonate Precipitation

Na2CO3 TSNaOH

2Li+ + Na2CO3 + NaOH→

Li2CO3↓ + 2Na+

(Soine and Wilson, 1967, p. 188)

Formation of white precipitate(USPCI, 2007, p. 140)

+carbonate salt of lithium is one of the slightly insoluble ones.(Soine and Wilson, 1967, p.188)

1-2 NH4Cl TS Solubility of the precipitate in NH4Cl TS

Li2CO3↓ + 2NH4Cl → (NH4)2CO3 + 2LiCl

(Soine and Wilson, 1967, p. 188)

Dissolution of white precipitate(USPCI, 2007, p. 140)

+ NH4Cl is an acidic salt hence it produces H3O+

upon hydrolysis.In the equilibriumCO3

2- + H2O ↔ HCO3

- + OH-, H3O+

will react with OH-, decreasing its amount and causing the equilibrium to further move to the right.

2 Flame Test HCl Li+ + HCl → LiCl + H+

LiCl ∆→

Li↑ + Cl↑

Li↑ ∆→

Li*

Li* → Li↑ + hv(Petrucci and Harwood, 1997, p. 766)

Formation of carmine-red color on non-luminous flame(USPCI, 2007, p. 140)

Salts of alkali metals are mostly soluble in water. Therefore, the flame test good way of detecting such ions.

3 Reaction with H2SO4

2N H2SO4 Li+ + H2SO4 no reaction(USPCI, 2007, p.140)

Clear colorless solution(USPCI, 2007, p.140)

Sulfate salt of lithium is soluble in water unlike that of strontium

(Soine and Wilson, 1967, p.188)

II. Na+

1-1 Reaction with K2CO3

15% K2CO3 2Na+ + K2CO3 → Na2CO3 + 2K+

(USPCI, 2007, p. 141)(Soine and Wilson, 1967, p.193)

Formation of colorless solution without precipitation(USPCI, 2007, p. 141)

Sodium carbonate is soluble in water(Soine and Wilson, 1967, p.216)

1-2 Precipitation of Sodium Pyroantimonate

KH2SbO4

TSNa2CO3 + 2KH2SbO4

∆→

Na2H2Sb2O7↓ +

K2CO3 + H2O (Soine and Wilson, 1967, p.193)

Formation of white dense precipitate(USPCI, 2007, p. 141)

Sodium pyroantimonate in nearly insoluble in water.(Soine and Wilson, 1967, p.193)

2 Flame Test HCl Na+ + HCl → NaCl + H+

NaCl ∆→

Na↑ + Cl↑

Na↑ ∆→

Na*

Na* → Na↑ + hv(Petrucci and Harwood, 1997, p. 766)

Formation of persistent golden-yellow color on non-luminous flame(USPCI, 2007, p. 141)

Salts of alkali metals are mostly soluble in water. Therefore, the flame test good way of detecting such ions.

III. K+

1 Flame Test HCl K+ + HCl → KCl + H+

KCl ∆→

K↑ + Cl↑

K↑ ∆→

K*

K* → K↑ + hv(Petrucci and Harwood, 1997, p. 766)

Formation of violet color on non-luminous flame(USPCI, 2007, p. 141)

Salts of alkali metals are mostly soluble in water. Therefore, the flame test good way of detecting such ions.

2-1 Precipitation of Potassium Bitartrate

NaHC4H4O6

TSK+ + NaHC4H4O6 → KHC4H4O6↓ + Na+

(Soine and Wilson, 1967, p. 270)Formation of white crystalline precipitate(USPCI, 2007, p. 141)

Potassium bitartrate is insoluble in water(Soine and Wilson, 1967, p. 271)

2-2 Solubility of Potassium Bitartrate in

6N NH4OH KHC4H4O6↓ + NH4OH → NH3↑ + KOH + H2C4H4O6

Dissolution of precipitate with pungent odor

6N NH4OH (USPCI, 2007, p. 141)2-2 Solubility of Potassium Bitartrate inNaOH

NaOH KHC4H4O6↓ + NaOH → KNaC4H4O6 + H2O Dissolution of precipitate(USPCI, 2007, p. 141)

2-3 Effect of glacial acetic acid on the precipitation of Potassium Bitartrate

NaHC4H4O6

TSEthanol

K+ + NaHC4H4O6 KHC4H4O6↓ + Na+

(Soine and Wilson, 1967, p. 270)

Faster formation of white crystalline precipitate(USPCI, 2007, p. 141)

2-4 Effect of ethanol on the precipitation of Potassium Bitartrate

NaHC4H4O6

TSGlacial

Acetic Acid

K+ + NaHC4H4O6 KHC4H4O6↓ + Na+

(Soine and Wilson, 1967, p. 270)

Faster formation of white crystalline precipitate(USPCI, 2007, p. 141)