Question

(a) Fig. 5.1 shows part of the structure of lithium chloride.

               

     (i) Deduce the formula of lithium chloride.
          formula = ………………………………
     (ii) Lithium chloride has a high melting point of 605°C.
          Explain why lithium chloride has a high melting point.

(b) Fig. 5.2 shows part of the structure of graphite.

       

    (i) Describe the structure of graphite.

    (ii) Explain why graphite is used as a lubricant.
         Use ideas about structure and bonding.

(c) Mercury is a liquid at room temperature, 25°C.
      (i) Tick (✓) the row in Table 5.1 which shows the melting point and boiling point of mercury.

         

      (ii) Mercury has a proton number (atomic number) of 80 and a nucleon number (mass number) of 201.
            Complete Table 5.2 for an atom of mercury.

           

▶️Answer/Explanation

Ans : 

5(a)(i) LiCl ;

5(a)(ii) idea that lithium chloride has (strong electrostatic) forces of attraction / bonds between (oppositely charged) ions ;
               idea that the forces / bonds need lots of energy to overcome ;

5(b)(i) Any two from:
               giant covalent ;
               layers (of carbon atoms) ;
               each carbon atom is (covalently) bonded / joined to 3 other (carbon) atoms ;

5(b)(ii) idea that there are weak forces between the layers (of carbon atoms) ;
                 (so) the layers can slide ;

5(c)(i) –39 and 357 √;

5(c)(ii)