MCQ practice · SSC Chemistry Board questions · Chapter 6: Concept of Mole and Chemical Counting
Which is the formula of aluminium carbonate?
Think it through first, then pick an option.
- a AlCO₃
- b Al₂CO₃
- c Al₂(CO₃)₃
- d Al(CO₃)₃
Answer and explanation
Correct answer: c Al₂(CO₃)₃
2 Al³⁺ (+6) and 3 CO₃²⁻ (−6): Al₂(CO₃)₃.
Why the other options are wrong
- a AlCO₃: Crossing the valencies of Al³⁺ and CO₃²⁻ gives Al₂(CO₃)₃; in AlCO₃ the charges do not balance.
- b Al₂CO₃: Al₂CO₃ has one carbonate, so +6 against −2; it does not balance.
- d Al(CO₃)₃: Al(CO₃)₃ has −6 against +3; it does not balance.
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