Class 10 Chemical Bonding Mock Test (ICSE)

Topics in Chemical Bonding

• Electrovalent bond formation
• Covalent bond formation
• Properties of electrovalent and covalent compounds
• Coordinate bond: hydronium and ammonium ions
• Polar and non-polar covalent compounds

Chemical Bonding practice questions with answers

1. Q1Multiple choice·1 mark
   Which of the following molecules contains a triple covalent bond?

   1. (a)$H_2$
   2. (b)$O_2$
   3. (c)$H_2O$
   4. (d)$N_2$
   Show answer and step marks

   1. Correct option: (d) $N_2$+1

   Answer: (d)
2. Q2Multiple choice·1 mark
   Which of the following is a polar covalent compound?

   1. (a)$HCl$
   2. (b)$CH_4$
   3. (c)$O_2$
   4. (d)$Cl_2$
   Show answer and step marks

   1. Correct option: (a) $HCl$+1

   Answer: (a)
3. Q3Multiple choice·1 mark
   A coordinate bond is formed by:

   1. (a)Equal sharing of electrons between two atoms
   2. (b)Transfer of electrons from a metal to a non-metal
   3. (c)Electrostatic attraction between oppositely charged ions
   4. (d)Sharing of a pair of electrons contributed by only one of the combining atoms
   Show answer and step marks

   1. Correct option: (d) Sharing of a pair of electrons contributed by only one of the combining atoms+1

   Answer: (d)
4. Q4Multiple choice·1 mark
   A chlorine atom has atomic number 17. How many electrons are present in its outermost shell?

   1. (a)7
   2. (b)17
   3. (c)8
   4. (d)2
   Show answer and step marks

   1. Correct option: (a) 7+1

   Answer: (a)
5. Q5Long answer·4 marks
   Atomic numbers: hydrogen = 1, nitrogen = 7, oxygen = 8, chlorine = 17. (a) Define a covalent bond. [1] (b) Write the electronic configuration of a chlorine atom. [1] (c) State the number of electron pairs shared between the two nitrogen atoms in a nitrogen molecule $N_2$. [1] (d) In a water molecule $H_2O$, the oxygen atom shares electrons with two hydrogen atoms. Find the number of lone pairs of electrons on the oxygen atom. [1]
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   1. (a) Covalent bond: a chemical bond formed by mutual sharing of one or more pairs of electrons between two atoms (usually non-metal atoms) to attain a stable noble gas configuration.+1
   2. (b) Chlorine (Z = 17) has the electronic configuration 2, 8, 7.+1
   3. (c) Each nitrogen atom has 5 valence electrons and needs 3 more to complete its octet, so the two atoms share 3 electron pairs.+1
   4. (d) Oxygen has 6 valence electrons; 2 are used in bonding with the two hydrogen atoms, leaving 4 electrons, which form 2 lone pairs.+1

   Answer: (a) A covalent bond is the mutual sharing of one or more pairs of electrons between two atoms to attain a noble gas configuration; (b) 2, 8, 7; (c) 3 pairs of electrons (a triple bond); (d) 2 lone pairs of electrons
6. Q6Long answer·4 marks
   Ammonia (NH$_3$) and water (H$_2$O) each react with a hydrogen ion, H$^+$, which has no electrons of its own. Use the electron data of the atoms involved to answer the following. (a) Calculate the total number of valence electrons in one molecule of ammonia, NH$_3$. [1] (b) Name the type of bond formed when a hydrogen ion combines with an ammonia molecule to form the ammonium ion, NH$_4^+$. [1] (c) Identify the atom that supplies both electrons of the shared pair in the bond named in part (b). [1] (d) Calculate the number of electrons in the outermost shell of the oxygen atom in the hydronium ion, H$_3$O$^+$, formed when a hydrogen ion combines with a water molecule. [1]
   Show answer and step marks

   1. (a) Valence electrons: N has 5 and each H has 1, so total = $5 + 3 \times 1$+1
   2. (b) A bond in which both shared electrons come from one atom, with the hydrogen ion accepting them, is a coordinate bond (dative covalent bond)+1
   3. (c) The nitrogen atom of ammonia supplies the lone pair of electrons+1
   4. (d) Oxygen in H$_3$O$^+$ has 3 bonding pairs (6 electrons) and 1 lone pair (2 electrons), so outer shell electrons = $6 + 2$+1

   Answer: (a) 8 valence electrons; (b) coordinate bond (dative covalent bond); (c) nitrogen atom (of NH$_3$); (d) 8 electrons

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