Question

When $C{O_2}$ is passed into aqueous ${K_2}Cr{O_4}$ solution, this changes to another colour. What is another colour?
A) Black
B) Yellow
C) Pink
D) orange

Answer 1

We need to know that the chemical properties of the gas depend on the mixture of gases. All the gases are not helpful for the human body. Some gases are poisonous for the human body. It leads to death also. For example, wrong inhalation of carbon dioxide in the human body leads to death. Some cyanide gases and mono and dioxide gases also lead to human death in the world. In plants during the day time they inhale carbon dioxide from the atmosphere and exhale oxygen, but in the night time they inhale oxygen and exhale carbon dioxide.

Complete answer:
The carbon dioxide reacts with water to form carbonic acid.
The reaction for discussion is given below,
$C{O_2} + {H_2}O \to {H_2}C{O_3}$
The carbonic acid is the acid, once it reacts ${K_2}Cr{O_4}$ to give the product of chromate anion, the colour of the chromate anion is orange.
The chemical reaction for the above discussion is given below,
$2{K_2}Cr{O_4} + {H_2}C{O_3} \to C{r_2}{O_7}^{2 - } + {H_2}O + {K_2}C{O_3}$
According to the above discussion, we conclude is When $C{O_2}$ passes into aqueous ${K_2}Cr{O_4}$solution, this changes to another colour which is orange.

So, the correct answer is “Option D”.

Note:
According to the Arrhenius concept one substance said to acid means, acid is nothing but a substance that dissociates to give hydrogen ion when decomposed in the water.
Examples of Arrhenius acids are hydrochloric acid (${\text{HCl}}$), sulphuric acid (${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$), nitric acid (${\text{HN}}{{\text{O}}_{\text{3}}}$) etc,.
According to Arrhenius concept one substance said to base means, bases is nothing but a substance that dissociates to give hydroxyl ion when decomposed in water.
Examples of Arrhenius bases are sodium hydroxide (${\text{NaOH}}$), calcium hydroxide (${\text{Ca(OH}}{{\text{)}}_{\text{2}}}$) etc,.
But, Arrhenius theory has some limitations. One of the main limitations is not being able to explain the behaviour of acids and bases in non-aqueous solvents such as acetone etc,. It is not able to explain the acid which doesn't contain hydrogen and bases don’t contain hydroxyl ion in the formula. Ammonia is a well known base that is not accepted as base in Arrhenius base. These limitations are recovered by further coming theories like the Bronsted and Lowry concept of acids and bases.