Tag: chemistry

Questions Related to chemistry

Action of $PCl _5$ on $SO _2$ chiefly yields :

chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

  1. $POCl _3$

  2. $P _4S _3$

  3. $SO _2Cl _2$

  4. $SO _3$

Show answer
Correct Option: A
Explanation:

$PCl _{5}+SO _{2}\rightarrow POCl _{3}+SOCl _{2}$

Unsymmetrical $PCl _5(s)$ splits into $PCl _4^+$ and  $PCl _6^-$.

chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

  1. True

  2. False

  3. Ambiguous

  4. None of these

Show answer
Correct Option: A
Explanation:

The cation $PCl^+ _4$ and the anion $PCl _6^-$ are tetrahedral and octahedral which are more stable then $PCl _5$ due to symmetry.

$PCl _5$ in soild state dissociates into $PCl^+ _4$ and $PCl^- _6$.

chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

The given statement is True.
 
$\displaystyle PCl _5$ molecule has trigonal bipyramidal geometry which is unstable as axial P-Cl bonds are slightly larger than equatorial P-Cl bonds. Also some bond angles are of 90 deg and others are of 120 deg. Due to this, trigonal bipyramidal geometry is not regular and not stable. Hence, in solid state, $\displaystyle PCl _5$ molecule dissociates into tetrahedral $\displaystyle [PCl _4]^+$ and octahedral $\displaystyle [PCl _6]^-$
$\displaystyle 2PCl _5 \rightleftharpoons [PCl _4]^+ +[PCl _6]^- $

The compound molecular in nature in gas phase but ionic in solid state is :

chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

  1. $ PCl _5 $

  2. $ CCl _4 $

  3. $ PCl _3 $

  4. $ POCl _3 $

  5. None of the above

Show answer
Correct Option: A
Explanation:

In gaseous and molten state $PCl _5$ is neutral molecule with trigonal bipyramidal symmetry.

In solid state $PCl _5$ is ionic which forms $PCl _4^{+}$, $PCl _6^{-}$. The cation and anion $PCl _4^{+}$, $PCl _6^{-}$ are tetrahedral and octahedral respectively.

Hence option A is correct.

What is a chemical change?

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. Change in size, shape

  2. Change from one substance to another new substance

  3. Change in temperature from lower to higher

  4. None of above

Show answer
Correct Option: B
Explanation:

A chemical change is a process where one or more substances are converted into one or more new substances. Examples: Explosion of fireworks that produces heat, light, sound and unpleasant gases, breaking down of ozone in the ozone layer by the UV radiations.


Hence, the correct option is $B$

Which of the following cause a substance to change into an entirely new substance with a new chemical formula?

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. Physical change

  2. Chemical change

  3. Both A and B

  4. None of these

Show answer
Correct Option: B
Explanation:

When a substance undergoes chemical change, its chemical properties are altered.

Which of the following is not a chemical change?

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. Whipping eggs

  2. Burning wood

  3. Digestion

  4. All of above

Show answer
Correct Option: A
Explanation:

In whipping of eggs, the air is introduced into the fluid but no new substance is formed. Hence, it is a physical change. Digestion and burning of wood results in the formation of new substances. Thus, it is a physical change.


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

An example of chemical change is :
chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. water condensing on the outside of your cold beverage

  2. bending a wire

  3. slicing bread

  4. freezing water

  5. burning a candle

Show answer
Correct Option: E
Explanation:

Burning of candle is a chemical change because the wax gets converted into carbon dioxide whereas the rest of the options represent the physical change.


Hence the correct option is E.

Insoluble impurities from solution during crystallization are removed by :

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. drying

  2. filtration

  3. heating

  4. cooling

Show answer
Correct Option: B
Explanation:

Heating is the process of increasing the temperature of a body from its original temperature.

Cooling is the process of decreasing the temperature of a body from its original temperature.
Filtration is the process of separating small particles of solid matter from a liquid, by causing the liquid to pass through the pores of some substance, called a filter.
Insoluble impurities from solution during crystallization are removed by filtration as the insoluble solid particles passed through the filter.
Drying is the process of drying up the liquid present on any material by heating the material.
Option B is correct.

While forming crystals, it is important to :

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. evaporate to dryness to get purest possible crystals

  2. attach gas syringes to collect fumes

  3. not evaporate water of crystallization

  4. use high flames

Show answer
Correct Option: C
Explanation:

Crystals contain water of crystallization hence during formation of crystals water of crystallization should not be evaporated.

Also, crystallization is the process of formation of crystals. Crystals is defined as the highly organized molecule into a well-known structure.