Tag: chemistry

Questions Related to chemistry

Which of the following has more acidic in nature?

oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

  1. HClO

  2. HClO$ _2$

  3. HClO$ _3$

  4. HClO$ _4$

Show answer
Correct Option: D
Explanation:
Acidity of oxyacids of halogen increases with increase in oxidation number of halogen Oxidation number of CI in HCIO is + 1, HCIO$ _2$ is +3, HClO$ _3$ is + 5 and HCIO$ _4$ is + 7.
$\therefore$ HClO$ _4$ is most acidic among given choices.

Assertion: $HClO _4$ is a strong acid than $HClO _3$.
Reason: Oxidation state of Cl in $HClO _4$ is +7 and in $HClO _3$, it is + 5.

oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

  1. If both assertion and reason are true and the reason is a correct explanation of the assertion.

  2. If both assertion and reason are true but reason is not a correct explanation of the assertion

  3. If the assertion is true but reason is false

  4. If both the assertion and reason are false

  5. If the assertion is false but the reason is true

Show answer
Correct Option: A
Explanation:

Let us calculate the oxidation state of Cl in $HClO _4$ ;

$+1+ x + $ ($4 \times (-2)$ = 0
So,$ x = -1+8$
         $  = 7$
Hence. the oxidation state of Cl in $HClO _4$ is 7.
Let us calculate the oxidation state of Cl in $HClO _3$ ;
$+1+ x + $ ($3\times (-2)$ $= 0$

So, $x = -1+6$
         $= 5$
Hence. the oxidation state of Cl in $HClO _4$ is 5.

So, we conclude that the oxidation state of Cl is less  in $HClO _3$ than $HClO _4$

Bleaching powder loses its power on keeping for long time because :

oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

  1. it changes to calcium hypochlorite.

  2. it changes to calcium chloride and calcium hydroxide.

  3. it absorbs moisture.

  4. it changes to calcium carbonate and chlorine.

Show answer
Correct Option: D
Explanation:

Bleaching powder reacts with carbon dioxide in air to give chlorine and calcium carbonate.

$2Ca(ClO) _2 + 2CO _2 \rightarrow 2CaCO _3 + 2Cl _2 + O _2$

Choose the correct order of acidity order:

oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

  1. $\displaystyle { HClO < { HClO } _{ 2 } }$

  2. $\displaystyle { H } _{ 2 }{ SO } _{ 4 } > { H } _{ 2 }{ SO } _{ 3 }$

  3. $\displaystyle { H } _{ 3 }{ PO } _{ 2 } < { H } _{ 3 }{ PO } _{ 3 }$

  4. $\displaystyle { HNO } _{ 3 } > { HNO } _{ 2 }$

  5. $\displaystyle { HF > { HCl } }$

  6. $\displaystyle { H } _{ 3 }{ PO } _{ 3 } > { H } _{ 3 }{ PO } _{ 4 }$

Show answer
Correct Option: A,B,D,F
Explanation:

The acidic character of oxyacids increases with increase in the oxidation state. 


More is the number of $O$ atoms bonded, more electrons will be pulled away from $O-H$ bond, weaker will be the $O-H$ bond and stronger will be the acid. Hence, $\displaystyle
HClO < HClO _2$, $\displaystyle H _2SO _4 > H _2SO _3$ and $\displaystyle HNO _3 > HNO _2$

For options C and F, the correct order is $\displaystyle H _3PO _2 < H _3PO _4 < H _3PO _3$ because  $H _3PO _3$ is polar.

The increase in the acidity is small as the number of unprotonated oxygen, responsible for the enhancement of acidity due to inductive effect remains the same. $HCl$ is more acidic than $HF$ due to strong $H-F$ bond (high bond dissociation enthalpy), high heat of dehydration for $HF$ due to an association in solution due to hydrogen bonding and low electron affinity of fluorine atom.

What are the corresponding anhydrides of the following oxyacids:

$\displaystyle { HClO } _{ 4 }$, $\displaystyle { HClO } _{ 3 }$, $\displaystyle { HClO } _{ 2 }$ and $\displaystyle { HOCl }$.

oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

  1. $\displaystyle { HClO } _{ 4 }:{ Cl } _{ 2 }{ O } _{ 3 }$

  2. $\displaystyle { HClO } _{ 3 }:{ Cl } _{ 2 }{ O } _{ 6 }$

  3. $\displaystyle { HClO } _{ 2 }:{ Cl }O _{ 2 }$

  4. $\displaystyle { HOCl }:{ Cl } _{ 2 }{ O _4 }$

Show answer
Correct Option: B,C
Explanation:
Anhydrides of oxyacids are given as:

$\displaystyle { HClO } _{ 4 }:{ Cl } _{ 2 }{ O } _{ 7 }$

$\displaystyle { HClO } _{ 3 }:{ Cl } _{ 2 }{ O } _{ 6 }$

$\displaystyle { HClO } _{ 2 }:{ Cl }O _{ 2 }$

$\displaystyle { HOCl }:{ Cl } _{ 2 }{ O }$

Hydrogen fuel is used in:

chemistry occurrence of carbon compounds in nature substances, objects and energy alternative fuels and energy sources alternative sources of energy

  1. liquid-propellant rockets

  2. portable fuel cell applications

  3. cars

  4. all of above

Show answer
Correct Option: D
Explanation:

Hydrogen fuel can provide motive power for liquid-propellant rockets, cars, boats and airplanes, portable fuel cell applications or stationary fuel cell applications, which can power an electric motor. The problems of using hydrogen fuel in cars arise from the fact that hydrogen is difficult to store in either a high pressure tank or a cryogenic tank.

We can save energy by :

chemistry occurrence of carbon compounds in nature substances, objects and energy alternative fuels and energy sources alternative sources of energy

  1. buying expensive cars

  2. using aeroplanes

  3. using CFL

  4. using ships

Show answer
Correct Option: C
Explanation:

Simple things like switching off fans and lights when not in use, using maximum daylight, walking instead of driving for short distances, using CFL instead of traditional bulbs, proper insulation for leakage of energy can go a long way in saving energy.


Hence the correct option is C.

Which of the following is/are the method(s) of controlling hydrocarbons from production?

chemistry occurrence of carbon compounds in nature substances, objects and energy alternative fuels and energy sources alternative sources of energy

  1. Adsorption

  2. Condensation

  3. Gas Absorption

  4. All of the above

Show answer
Correct Option: D
Explanation:

The methods of controlling hydrocarbons from production are

  1. Adsorption
  2. Condensation
  3. Gas absorption

What is the effect of strike of unions in oil producing companies?

chemistry occurrence of carbon compounds in nature substances, objects and energy alternative fuels and energy sources alternative sources of energy

  1. decrease in price of oil

  2. cause an energy crisis.

  3. suspension of unions by Govt.

  4. increase in the selling of cars

Show answer
Correct Option: B
Explanation:

A strike by unions in an oil producing firm can definitely cause an energy crisis.

What are the disadvantages of renewable energy?

chemistry occurrence of carbon compounds in nature substances, objects and energy alternative fuels and energy sources alternative sources of energy

  1. They are eco-friendly

  2. They cannot be used in war

  3. Proper equipment to convert those energy into useful form is not available easily

  4. They are non-renewable

Show answer
Correct Option: C
Explanation:

There are many advantages of renewable energy but the only disadvantage is that proper equipment for their conversion are not easily available. Either they are very costly or not easily available.