Tag: chemistry

Quizzes (490) Questions (9892)

Questions Related to chemistry

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

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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]^- $

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

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

  1. $ PCl _5 $
  2. $ CCl _4 $
  3. $ PCl _3 $
  4. $ POCl _3 $

  5. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

What is a chemical change?

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $B$

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

Which of the following is not a chemical change?

  1. Whipping eggs

  2. Burning wood

  3. Digestion

  4. All of above
Reveal answer Fill a bubble to check yourself
A Correct answer
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 $\text{A}$

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

  1. water condensing on the outside of your cold beverage

  2. bending a wire

  3. slicing bread

  4. freezing water

  5. burning a candle
Reveal answer Fill a bubble to check yourself
E Correct answer
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.

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

Insoluble impurities from solution during crystallization are removed by :

  1. drying

  2. filtration

  3. heating

  4. cooling
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

While forming crystals, it is important to :

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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.