Tag: endothermic and exothermic reactions

Questions Related to endothermic and exothermic reactions

During the reaction of some metals with dilute hydrochloric acid, the following observations were made. The temperature of the reaction mixture rises when aluminium (Al) is added mainly because :

                       

chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

  1. Heat is evolved

  2. Due to the catalyst

  3. It is an endothermic reaction.

  4. It is an exothermic reaction.

Show answer
Correct Option: A,D
Explanation:

The temperature of the reaction mixture rises beacause, the following exothermic reaction takes place:

$2Al(s)  +  6HCl(aq)  \rightarrow   2AlCl _{3}(aq)  +  3H _{2}(g)  +  heat$

Decomposition of ferrous sulphate is a/an:

chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

  1. precipitation reactions

  2. exothermic reactions

  3. endothermic reactions

  4. Synthesis reactions

Show answer
Correct Option: C
Explanation:

Decomposition of ferrous sulphate is an endothermic reaction as it involves absorption of heat to form ferric oxide ($Fe _{2}O _{3}$), sulphur dioxide ($SO _{2}$) and sulphur trioxide ($SO _{3}$). The equation for this reaction can be written as:
$ 2FeSO _{4}(s)  \overset{heat}{\rightarrow}  Fe _{2}O _{3}(s)  +  SO _{2}(g)  +  SO _{3}(g)$

During the reaction of some metals with dilute hydrochloric acid,
following observations were made. 
 
The reaction of sodium metal is found to be highly explosive because:

chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

  1. Heat is evolved

  2. Due to the catalyst

  3. It is an endothermic reaction.

  4. It is an exothermic reaction.

Show answer
Correct Option: A,D
Explanation:

Reaction of sodium with hydrochloric acid is highly exothermic one and therefore explosive in nature.
$2Na(s)  +  2HCl(aq)  \rightarrow   2NaCl(aq)  +  H _{2}(g)$  +  heat

Dilution of sulphuric acid is a/an:

chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

  1. synthesis reaction

  2. exothermic reaction

  3. endothermic reaction

  4. none of these

Show answer
Correct Option: B
Explanation:

Dilution of sulphuric acid with water is a highly exothermic process as it occurs with the evolution of heat. The equation for this reaction  can be wriiten as:
$H _{2}SO _{4}  +  2H _{2}O  \rightarrow   2H _{3}O^{+}  +  SO _{4}^{2-}  +  heat$

Which of the following are endothermic process?

chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

  1. boiling of water

  2. dissolving salts in water

  3. dissolving conc. $H _2SO _4$ in water

  4. evaporation of water

Show answer
Correct Option: A,B,D
Explanation:
  1. Boiling of water would be an endothermic process because the system (water) is absorbing heat to turn into vapour. Hence both option 1 $ 3 are endothermic.
     And the reverse process would therefore be exothermic.

    2. Addition of Conc. acids to water is an exothermic reaction.

Chemical reactions occur with absorption of heat energy are called:

chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

  1. precipitation reactions

  2. exothermic reactions

  3. endothermic reactions

  4. synthesis reactions

Show answer
Correct Option: C
Explanation:

The term endothermic process describes a process or reaction in which the system absorbs energy from its surroundings in the form of heat where in case of exothermic it releases energy to the surroundings. 

Which of the following is/are endothermic reactions?

chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

  1. $CaCO _{3}\rightarrow CaO+CO _{2}$

  2. $CH _{4}+2O _{2}\rightarrow CO _{2}+2H _{2}O$

  3. $2HgO\rightarrow 2Hg+O _{2}$

  4. $2H _{2}+O _{2}\rightarrow 2H _{2}O$

Show answer
Correct Option: A,C
Explanation:
$CaCO _{3}\rightarrow CaO+CO _{2}$
is a decomposition reaction and requires energy for breaking bonds. Its an endothermic reaction.
$CH _{4}+2O _{2}\rightarrow CO _{2}+2H _{2}O$
Its a combustion reaction hence releases energy and is an exothermic reaction
$2HgO\rightarrow 2Hg+O _{2}$
is a decomposition reaction and requires energy for breaking bonds. Its an endothermic reaction.
$2H _{2}+O _{2}\rightarrow 2H _{2}O$
Its a combustion reaction hence releases energy and is an exothermic reaction
Thus A and D are endothermic reactions. Option A and D are correct

In endothermic reactions:

chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

  1. reactants have more energy than products

  2. reactants have less energy than products

  3. reactants and products have same energy

  4. reactants have lower temperature than products

Show answer
Correct Option: B
Explanation:

An endothermic occurs if the products have a higher energy level than the reactants and $\Delta H$ will be positive. In other words, reactants have lesser energy than products.

In an exothermic reaction, the reacting mixture absorbs heat from the surroundings. Therefore, the reactants will have higher energy than the product here.

So the answer is option B.

For per gram reactant, the maximum quantity of ${ N } _{ 2 }$ gas is produced in which of the following thermal decomposition reaction? (Given: Atomic wt. Cr=52 u, Ba=137 u)
chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions
  1. $(NH _4) _2Cr _2O _7(s) \rightarrow N _2(g) + 4H _2O(g)+Cr _2O _3(s)$
  2. $2NH _4NO _3(s) \rightarrow 2N _2(g) + 4H _2O(g)+O _2(g)$
  3. $Ba(N _3) _2(s) \rightarrow Ba(s) + 3N _2(g)$
  4. $2NH _3(g) \rightarrow N _2(g) + 3H _2(g)$
Show answer
Correct Option: B

The time required to complete $\dfrac{3}{4}th$ of first order reaction is $32 min.$ then find $t _{\frac{1}{2}} = ?$

chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

  1. $16$

  2. $160$

  3. $1600$

  4. $32$

Show answer
Correct Option: A
Explanation:

$t _{\dfrac{3}{4}} = 2t _{\dfrac{1}{2}} = 32min.$
$t _{\dfrac{1}{2}} = 16min.$