When the hydrogen chloride concentration doubles, the number of collisions between the reactants (1. decreases 2. increases 3. remains constant), which causes the rate of the forward reaction to (1. decrease 2.increase 3. remain constant)

The correct answers :  2. increases ; 2. increase.

The rate reaction is depends on the number of factors such as concentration, temperature and catalyst use. The concentration of reactants is one such factors. If the concentration of the reactants doubles, more reactant particles move together, thus collision between reactants increases and the reaction rate is also increased. Therefore, higher the concentration of reactants, the faster the rate of a reaction.  

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.