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Class 9 · Science · Chemistry · Atoms and Molecules

Writing Chemical Formulae MCQs

Practice Writing Chemical Formulae multiple-choice questions from Atoms and Molecules (Class 9 Science) - tap an answer for instant feedback and a step-by-step solution. Practice the full set free on the RankByte app.

Writing Chemical FormulaeQuiz - Solve & Score

  1. Q1. A chemist drops sodium into a flask rich in chloride ions; using the criss-cross method, what formula does the salt that settles take?

    • A.NaCl
    • B.Na2Cl2
    • C.Na2Cl
    • D.NaCl2

    Answer: A. NaCl

    Sodium has valency 1 and chloride has valency 1. Criss-crossing gives sodium subscript 1 and chloride subscript 1, reduced to NaCl.

  2. Q2. Heated in air, a strip of magnesium grabs oxide and turns into a powdery solid; what chemical formula describes that product?

    • A.MgO2
    • B.Mg2O
    • C.MgO
    • D.Mg2O2

    Answer: C. MgO

    Magnesium has valency 2 and oxide has valency 2. Criss-crossing gives magnesium subscript 1 and oxide subscript 1, reduced to MgO.

  3. Q3. On a worksheet a learner must marry aluminium (valency 3) to oxide (valency 2); which formula belongs in the answer box?

    • A.Al3O2
    • B.Al3O3
    • C.Al2O3
    • D.AlO

    Answer: C. Al2O3

    Aluminium has valency 3 and oxide has valency 2. Criss-crossing gives aluminium subscript 2 and oxide subscript 3, reduced to Al2O3.

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More topics in Atoms and Molecules

Atomic Mass and Molecular MassChemical FormulaeLaws of Chemical CombinationLaws of Chemical Combination (Conservation of Mass, Constant Proportions)Laws of chem combination, mole concept, formulaeMole ConceptMole Concept and Avogadro's NumberMolecular and Formula Mass
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