Four substances, P, Q, R and S, are examined as follows. Test results: - On adding dilute hydrochloric acid: - P: a gas is released which ‘pops’ with a lighted splint - Q: a gas is released which turns limewater milky - R: no change - S: no change - On adding dilute aqueous sodium hydroxide and warming gently: - P: no change - Q: no change - R: a gas is released which turns damp red litmus paper blue - S: no change Which substances are P, Q, R and S?
- AP = Mg, Q = Na$_2$CO$_3$, R = NH$_4$Cl, S = NaCl
- BP = Mg, Q = NH$_4$Cl, R = Na$_2$CO$_3$, S = NaCl
- CP = Mg, Q = Na$_2$CO$_3$, R = NaCl, S = NH$_4$Cl
- DP = Na$_2$CO$_3$, Q = Mg, R = NaCl, S = NH$_4$Cl