Question

Which of the following statements are incorrect
(A) pH of acid rain is greater than 5.
(B) \[{N_2}O\] is a greenhouse gas
(C) \[N{O_3}^ - \] concentrations above 50 ppm causes blue baby syndrome

Answer 1

Hint: In such questions, where options are not directly related to each other, you should always analyze each sentence at one time. As the compounds mentioned in the options are mostly pollutants, their increased amount will always affect the life of all living beings. Look for the effects that the pollutants are causing, if they are not negative, they should be incorrect.

Complete answer:Let’s discuss each one of the statements to find out which are incorrect.
pH of normal, clean rain is around 5.0 – 5.5, making it slightly acidic, as carbon dioxide in the atmosphere dissolves in the rainwater, resulting in the formation of carbonic acid, which is a weak acid. When pollutants such as nitrogen oxides and sulpher dioxide dissolves in the rain water, it forms compounds such as nitrous acid \[\left( {HN{O_2}} \right)\] , nitric acid \[\left( {HN{O_3}} \right)\] , and sulphurous acid \[\left( {{H_2}S{O_3}} \right)\] , the pH of the rain drops to the value around 4.0. Hence it is called acid rain. Hence the first sentence is incorrect.
Greenhouse gases are capable of absorbing heat and entrapping it in the atmosphere, which obviously results in an effect called ‘Global Warming’. Like many known greenhouse gases, \[{N_2}O\] , nitrous oxide is also a greenhouse gas. Nitrous oxides have been excessively released into the atmosphere as a result of pollution, and it is also dangerous because of its life span of 114 years into the atmosphere and its ability to convert into nitrogen oxides in the presence of sunlight and oxygen, and nitrogen oxides are well known to damage the ozone layer. Hence the second sentence is absolutely correct.
Blue baby syndrome, also known as Methaemoglobinaemia is a condition where the ability of blood to carry vital oxygen decreases. The most common reason is the presence of nitrate in the drinking water. It becomes a serious concern in rural areas as they are dependent on rivers for their water and they don’t have adequate facilities to purify water. It can be controlled by keeping the level of nitrates under 50 ppm. Hence the statement 3 is also correct.

So, only option one is incorrect out of the three statements.

Note:Such questions always need a thorough knowledge of the topic, as the options might not be always related. Make sure that you either read the chapters properly, else you practice enough questions to completely cover the entire topic.