The reaction between calcium carbonate (caco3) and hcl produces calcium chloride (cacl2), carbon dioxide (co2), and water (h2o).what happens when the concentration of hydrogen chloride (hcl) molecules is doubled in this reaction? caco3 + 2hcl → cacl2 + co2 + h2o when the hydrogen chloride concentration doubles, the number of collisions between the reactants (increases, decreases, remains constant) , which causes the rate of the forward reaction to (increase, decrease, remain constant)

The given chemical reaction is between calcium carbonate and hydrochloric acid to produce calcium chloride, carbon dioxide and water. This reaction can be represented as,

When the concentration of the reactants is increased, the number of collisions that take place between the reactant molecules increases. This speeds up the reaction. Therefore, when the concentration of HCl is doubled as long as there is enough calcium carbonate to react with HCl, the number of effective collisions giving products increases, this causes the rate of forward reaction to increase.

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.