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Questions Related to chemistry

Among the following which will decrease the rate of the reaction?
i. Using highly concentrated reactants
ii. Decreasing the temperature by $25\ K$
iii. Stirring the reactants

chemistry how far? how fast? collision theory collision theory of chemical reactions rate of chemical reaction

  1. i only

  2. ii only

  3. i and iii only

  4. ii and iii only

  5. i, ii, and iii

Show answer
Correct Option: B
Explanation:

$\bullet $  Using highly concentrated reactants will increase the rate of the reaction as rate is directly proportional to the 

    concentration of reactants.
$\bullet $  Decreasing the temperature by 25 K will decrease the rate constant and hence the rate of reaction will decrease.
$\bullet $  Stirring the reactants increases the rate of interaction between the reactants and hence the rate of reaction increases.
$\therefore $ The correct answer is (ii) only.

_________ increases effective collisions without increasing average energy.

chemistry how far? how fast? collision theory collision theory of chemical reactions rate of chemical reaction

  1. An increase in the reactant concentration

  2. An increase in the temperature

  3. A decrease in pressure

  4. Catalysts

  5. $\displaystyle pH$

Show answer
Correct Option: A
Explanation:

An increase in the reactant concentration increase effective collisions without increasing average energy.

This is due to the fact that molecules comes more and more closer, hence, they tends to collide more easily.

In a reaction carried out at 400 k, $0.0001\%$ of the total number of collisions are effective. The energy of activation of the reaction is:

chemistry how far? how fast? collision theory collision theory of chemical reactions rate of chemical reaction

  1. zero

  2. 7.37 k cal/mol

  3. 9.212 k cal/mol

  4. 11.05 k cal/mol

Show answer
Correct Option: D
Explanation:

We know that, Arrhenius equation for calculation of energy of activation of reaction with rate constant $K$ and temeperature $T$ is 

$K=A$ $e^{-Ea/RT}$
where, $Ea$= Arrhenius activation energy
$A$= pre exponential factor (frequency factor)

Now, $e^{-Ea/K _BT}$= Fraction of collision having more than activation energy
where, $K _B=$ Boltzmann constant
Given, $T=400$ $K$       and effective collision= $0.0001$%

$\Rightarrow$ Effective Collision= $e^{-Ea/K _BT}$
$\Rightarrow$ $0.0001$%= $e^{-Ea/1.3\times 10^{-23}\times 400}$
$\Rightarrow$ $10^{-6}$= $e^{-Ea/1.3\times 10^{-23}\times 400}$

$\Rightarrow$ $2.303\times \log 10^{-6}$= $\cfrac {-Ea}{1.3\times 10^{-23}\times 400}$
$\Rightarrow$ $2.303\times (-6)$= $\cfrac {-Ea}{1.3\times 10^{-23}\times 400}$

$\Rightarrow$ $Ea$= $1.3\times 10^{-23}\times 400\times6\times 2.303=7.19\times 10^{-20}$ $J/mol$

Select the correct statement among the following.

chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

  1. Hydrogen chloride is prepared by passing chlorine gas through hot water

  2. Hydrogen chloride is produced by combination of moist hydrogen gas with chlorine in the presence of diffused sunlight

  3. Hydrogen chloride can't be produced in the dark

  4. Activated carbon is used as a catalyst in the synthesis of hydrogen chloride

Show answer
Correct Option: B,D
Explanation:
Hydrogen chloride is produced by a combination of moist hydrogen gas with chlorine in the presence of diffused sunlight. The reaction should be maintained in diffused but not in direct sunlight as it is an explosive reaction. And not even in dark as it is very slow (negligible). Activated carbon is used as a catalyst in the synthesis of hydrogen chloride.
Hence, options $B$ and $D$ are correct.

Moist hydrogen gas combines with chlorine in the presence of diffused sunlight to form $HCl$. The catalyst used here is :

chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

  1. oxygen.

  2. silica.

  3. alum.

  4. moisture.

Show answer
Correct Option: D
Explanation:

Moisture acts as a catalyst in the formation of HCl gas.


It acclerates the reaction.

It provides a reacting medium to hydrogen and chlorine gas.

It increases the interaction between them.


Hence, the correct option is $D$.


The reaction equation of the preparation of $HCl$ by synthesis is given by:

chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

  1. $NaCl + H _2SO _4 \rightarrow NaHSO _4+HCl$

  2. $NaHSO _4+NaCl \rightarrow HCl+NaSO _4$

  3. $H _2+Cl _2 \rightarrow 2HCl$

  4. None of these

Show answer
Correct Option: C
Explanation:
In the chloralkali process, brine (mixture of sodium chloride and water) solution is electrolyzed producing chlorine (Cl$ _2$), sodium hydroxide, and hydrogen (H$ _2$):

2 NaCl + 2 H$ _2$O → Cl$ _2$ + 2 NaOH + H$ _2$

The pure chlorine gas can be combined with hydrogen to produce hydrogen chloride in the presence of UV light:

Cl$ _2$(g) + H$ _2$(g) → 2 HCl(g)

As the reaction is exothermic, the installation is called an HCl oven or HCl burner. The resulting hydrogen chloride gas is absorbed in deionized water, resulting in chemically pure hydrochloric acid. This reaction can give a very pure product, e.g. for use in the food industry.

Hence, the correct option is $\text{C}$

In the laboratory preparation of $HCl$, which of the following are preferred?

chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

  1. Conc. $H _2SO _4$ as reactant

  2. Conc. $H _2SO _4$ as drying agent

  3. Temperature of reaction mixture below $200^0C$

  4. Use of activated carbon as catalyst

Show answer
Correct Option: A,B,C
Explanation:

The laboratory preparation of $HCl$ includes dehydration of hydrochloric acid with sulphuric acid. It can also be generated by the reaction of sulphuric acid with sodium chloride. 


The reaction occurs at room temperature. Sulphuric acid acts as a reactant as well as a drying agent.

$NaCl+H _2SO _4 \rightarrow NaHSO _4+HCl$

Hence, the correct options are $\text{A}$, $\text{B}$ and $\text{C}$

Metal chloride + Sulphuric acid$\longrightarrow$.............. + Hydrogen chloride :

chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

  1. Metallic sulphate

  2. Metallic bisulphate

  3. Metallic sulphide

  4. None of the above

Show answer
Correct Option: C
Explanation:

Metal chloride reaction with sulphuric acid is a double displacement reaction which form a metallic sulphate.

For example :-
$Na _2SO _4$ formed when $NaCl$ reacts with $H _2SO _4$ as

$\underset{chloride}{\underset{metal}{2NaCl}} + \underset{acid}{\underset{sulphuric}{H _2SO _4}} \xrightarrow{\Delta} \underset{Sulphate}{\underset{metallic}{Na _2SO _4}} + \underset{chloride}{\underset{Hydrogen}{2HCl}}$

The reaction of moist hydrogen gas with chlorine is explosive in the presence of :

chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

  1. hydrogen

  2. oxygen

  3. darkness

  4. direct sunlight

Show answer
Correct Option: D
Explanation:

The reaction of chlorine with moist hydrogen gas is explosive in case of direct sunlight.

In dark no reaction will take place because for activation light is required.
Hence, $HCl$ is prepared in presence of diffused sunlight.

Drying agents used in the purification of hydrogen chloride is/are:

chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

  1. conc. $H _2SO _4$

  2. $P _2O _5$

  3. $CaO$

  4. all of the above

Show answer
Correct Option: A
Explanation:

Conc. $H _2SO _4$ is a very strong drying agent and it is used in purification of hydrogen chloride.