The melting points of the two constitutional isomers are as follows: ortho-hydroxy acetophenone: 4-6 °c; para-hydroxy acetophenone: 109-111 °c. explain the large difference in melting points exhibited by these two compounds.

ortho-hydroxy acetophenone form intramolecular hydrogen bonding. On the other hand, para-hydroxy acetophenone forms intermolecular hydrogen bonding.

Explanation:

Hydrogen bonding:-

The bonding can be intramolecular and intermolecular. ortho-hydroxy acetophenone can form intramolecular hydrogen bonding which means that hydrogen bonding exist within the same molecule. On the other hand, para-hydroxy acetophenone forms intermolecular hydrogen bonding in which the bonding is in between the different molecules. Hence, more amount of energy is required to melt these molecules in case of para-hydroxy acetophenone.

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2