Class 9 Chemistry MCQs: Stoichiometery

MCQs (sample)

Showing 25 questions from this chapter. For a full timed test, use “Start online test”.

1. 1. What is the molar mass of sodium (Na)?

   • 23 g
   • 28 g
   • 44 g
   • 342 g
   Answer & explanation

   Correct: 23 g

   1 mole of Na weighs 23 g according to the given content.

2. 2. What does a chemical formula indicate about a compound?

   • The elements it contains and the ratio of atoms
   • The mass of the compound
   • The temperature at which it melts
   • The color of the compound
   Answer & explanation

   Correct: The elements it contains and the ratio of atoms

   A chemical formula reveals the elements present and the ratio of their atoms within the compound.

3. 3. What is a mole in chemistry?

   • A unit for counting particles
   • A type of molecule
   • A formula for calculating mass
   • A measurement of volume
   Answer & explanation

   Correct: A unit for counting particles

   A mole is a counting unit used by chemists to measure the amount of a substance, equivalent to 6.022 x 10^23 particles.

4. 4. What is a binary ionic compound composed of?

   • Mono-atomic metal cations and mono-atomic non-metal anions
   • Polyatomic ions only
   • Liquid molecules
   • Gaseous compounds
   Answer & explanation

   Correct: Mono-atomic metal cations and mono-atomic non-metal anions

   A binary ionic compound is defined as being composed of mono-atomic metal cations and mono-atomic non-metal anions.

5. 5. What does a structural formula show?

   • The arrangement of atoms in a compound
   • The total number of atoms only
   • Only the types of atoms present
   • The chemical reactions of a compound
   Answer & explanation

   Correct: The arrangement of atoms in a compound

   A structural formula shows how atoms are arranged in a compound.

6. 6. What is the symbolic representation of a chemical reaction called?

   • Chemical equation
   • Chemical formula
   • Reaction pathway
   • Balanced equation
   Answer & explanation

   Correct: Chemical equation

   The symbolic representation of a chemical reaction is called a chemical equation.

7. 7. What is the definition of molecular mass?

   • The sum of atomic masses of all atoms in a molecule
   • The weight of the molecule in grams
   • The number of atoms in a molecule
   • The ratio of cations to anions
   Answer & explanation

   Correct: The sum of atomic masses of all atoms in a molecule

   Molecular mass is defined as the sum of the atomic masses of all the atoms present in the molecule.

8. 8. How much does 9.05 moles of ozone (O3) weigh?

   • 434.4 g
   • 48 g
   • 28 g
   • 16 g
   Answer & explanation

   Correct: 434.4 g

   9.05 moles of O3 weigh 434.4 g as calculated from the molar mass of 48 g for 1 mole.

9. 9. What is the empirical formula for hydrogen peroxide?

   • HO
   • H2O2
   • H2O
   • O2H
   Answer & explanation

   Correct: HO

   The empirical formula of hydrogen peroxide is HO, representing a 1:1 ratio of hydrogen to oxygen.

10. 10. What does Avogadro's number represent?

    • The number of atoms in a mole
    • The mass of one mole of a substance
    • The volume of one mole of a gas
    • The number of molecules in a liter
    Answer & explanation

    Correct: The number of atoms in a mole

    Avogadro's number (6.022 x 10^23) represents the number of particles in one mole of a substance.

11. 11. In naming an ionic compound, which name comes first?

    • Cation name
    • Anion name
    • Metal name
    • Acid name
    Answer & explanation

    Correct: Cation name

    In the naming process, the cation is named first followed by the name of the anion.

12. 12. What does a molecular formula indicate?

    • Number of atoms of each element
    • Arrangement of atoms in space
    • Chemical properties of the compound
    • Type of chemical bonds present
    Answer & explanation

    Correct: Number of atoms of each element

    A molecular formula indicates the number of atoms of each element in the compound.

13. 13. Where are reactants located in a chemical equation?

    • On the left side
    • On the right side
    • Above the arrow
    • Below the arrow
    Answer & explanation

    Correct: On the left side

    Reactants are always written on the left side of the equation.

14. 14. How is the molecular mass of water (H2O) calculated?

    • H2: 2 + O: 16 = 18 amu
    • H2: 1 + O: 1 = 2 amu
    • H2: 1.008 + O: 16 = 17.008 amu
    • H2: 2 + O: 8 = 10 amu
    Answer & explanation

    Correct: H2: 2 + O: 16 = 18 amu

    The molecular mass of water is calculated as 2(1.008) + 16.00 = 18.016 amu, but it is rounded to 18 amu.

15. 15. What is the mass produced when 0.25 moles of carbon dioxide (CO2) is formed?

    • 11 g
    • 44 g
    • 28 g
    • 48 g
    Answer & explanation

    Correct: 11 g

    0.25 moles of CO2 produces 11 g, calculated from its molar mass of 44 g per mole.

16. 16. What is the empirical formula of glucose?

    • C6H12O6
    • CHO
    • C1H2O1
    • C1H1O1
    Answer & explanation

    Correct: CHO

    The simplest ratio of carbon, hydrogen, and oxygen atoms in glucose is 1:2:1, which gives the empirical formula as CHO.

17. 17. Which of the following has a gram atomic mass of 23 g?

    • Carbon (C)
    • Sodium (Na)
    • Zinc (Zn)
    • Water (H2O)
    Answer & explanation

    Correct: Sodium (Na)

    The gram atomic mass of Sodium (Na) is 23 g, which corresponds to its atomic mass of 23 amu.

18. 18. What suffix is added to the root name of a mono-atomic anion?

    • -ide
    • -ate
    • -ite
    • -ose
    Answer & explanation

    Correct: -ide

    The suffix -ide is added to the root name of the mono-atomic anion.

19. 19. What is the molecular formula of n-Butane?

    • C4H10
    • C3H8
    • C2H6
    • C5H12
    Answer & explanation

    Correct: C4H10

    The molecular formula of n-Butane is C4H10.

20. 20. What do the symbols 's', 'l', 'g', and 'aq' represent in a chemical equation?

    • States of matter
    • Chemical bonds
    • Types of reactions
    • Ionic compounds
    Answer & explanation

    Correct: States of matter

    's' stands for solid, 'l' for liquid, 'g' for gas, and 'aq' for aqueous, indicating physical states.

21. 21. What is the molecular mass of glucose (C6H12O6)?

    • 126.096 amu
    • 180.096 amu
    • 192.096 amu
    • 150.096 amu
    Answer & explanation

    Correct: 180.096 amu

    The molecular mass of glucose C6H12O6 is calculated as 6(12.00) + 12(1.008) + 6(16.00) = 180.096 amu.

22. 22. How many moles are in 5 g of hydrogen (H2)?

    • 2.48 moles
    • 2 moles
    • 1.25 moles
    • 3 moles
    Answer & explanation

    Correct: 2.48 moles

    5 g of H2 is equal to 2.48 moles based on its molar mass of 2.016 g per mole.

23. 23. Which of the following compounds has the same empirical and molecular formula?

    • Water
    • Glucose
    • Hydrogen peroxide
    • Benzene
    Answer & explanation

    Correct: Water

    Water (H2O) has the same empirical and molecular formula.

24. 24. How many molecules are in one mole of water (H2O)?

    • 6.022 x 10^23
    • 18.016
    • 2
    • 1
    Answer & explanation

    Correct: 6.022 x 10^23

    One mole of water contains 6.022 x 10^23 molecules, as defined in the content.

25. 25. Which of the following is the correct way to write the chemical formula for sodium chloride?

    • NaCl
    • Na2Cl2
    • NaCl2
    • Na+Cl-
    Answer & explanation

    Correct: NaCl

    The formula for sodium chloride is correctly written as NaCl, which indicates a neutral ionic compound.