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Atoms and Molecules — Science STD 9 — Question

Gujarat BoardEnglish MediumSTD 9ScienceAtoms and Molecules1 Mark
MCQ
In the following Questions, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following:
Assertion: The formula of aluminium sulphate is $Al_2(SO_4)_3$.
Reason: The valency of $Al$ is $3$ and charge on $SO_4{}^{2-}$.
  • ✓
    Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
  • B
    The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
  • C
    Assertion is true but the Reason is false
  • D
    The statement of the Assertion is false but the Reason is true.
✓

Answer

Correct option: A.
Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
$Al2 (SO4)_3$ is commonly known as aluminium sulphate.
There is two aluminium atom in aluminium sulphate, and because of this, the total valency of the formula is $6^+$.
Aluminium make positively charged ions, which makes the sulphate to have negatively charged ions.
Therefore, the valency of sulphate will be $2^-$ and aluminium is $3^+$ in aluminium sulphate.

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