Which of the following is always necessary for a chemical reaction to occur betw

Question

Which of the following is always necessary for a chemical reaction to occur between two reactants, A and B? A and B must be present in the same physical state There must be equal amounts of A and B present. A and B must be collide with sufficient energy and the proper orientation. The reaction must be carried out at room temperature. The reaction must be carried out at a temperature higher than room temperature. Which statement concerning energy changes in chemical reactions is FALSE? The breaking of bonds requires energy, and the formation of bonds releases energy. Activation energy is the minimum amount of energy required to initiate a chemical reaction. A reaction is exothermic if the products have a lower energy than the reactants. A reaction is endothermic if the reactants have a lower energy than the products. The overall energy change in a reaction is determined by the difference in energy between the products and the activated complex. Which of the following is FALSE about the energy diagram shown? The activation energy is 100 U. Point 2 on the diagram represents the activated complex. This reaction is exothermic. The energy of the products is lower than the energy of the reactants. 4) Which of the following statements concerning the reaction below ts FALSI? 2HgO(s) - 2Hg(/) + 0>( ) AH - 182 kJ A) There is an increase in entropy in this reaction. B) This reaction is endothermic. C 182 kJ of energy an.- required for every two moles degree f $ D) The energy of the reactants is greater than the energy of the products. E) the system absorbs energy from the surroundings in this reaction.

Explanation / Answer

1) it is not necessary the A and B must be in same physical state

unequal amount of A and B also can react

the reactions can take place above or below the room temperature

now

A and B must collide with sufficient energy and proper oreintation

this statement is correct

so

answer ( C)

2)

we know that

the overall energy change = energy of products - energy of reactants

so

the false statement is

E) the overall energy change in a reaction is determined by the diff ine E between products and activated complex

3)

in this case

activation energy = energy at 2 - energy at 1

activation energy = 100 - 75

activation energy = 25

now

dH = energy at 3 - energy at 1

dH = 25 - 75

dH = -50

so

this reaction is an exothermic reactions

So

the false statement is

A) the activation enery is 100 kJ

4)

2 Hg0 (s) ---> 2 Hg(s) + 02 (g)

we know that

entropy order is

gas > liquid > solids

as there are liquids and gases in the products

the entropy is increased

given

dH = + ve

so

the reaction is endothermic

for enodthermic reactions

energy of reactants is less than the energy of products

so

the false statement is

D) the energy of reactants is greater than the energy of products

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