Question

Consider the following statements :
A.) pH of NaCl solution is 7.
B.) Copper sulphate gives red colour with universal indicator.
C.) Degreasing of metals can be done with ${H_2}S{O_4}$.
Which of the above statement(s) is/are correct ?
a.) Only (B)
b.) (A) and (B)
c.) (B) and (C)
d.) Only (C)

Answer 1

Hint: The aqueous solution of NaCl is neutral. Universal indicators show blue colour if solution is basic in nature, green is solution is neutral and red when solution is acidic. Degreasing is the process of removal of oil and stain from metal. The Sodium hydroxide is used for degreasing.

Complete answer:
Let us see all the statements one by one and then see which is the correct statement.
The first statement is that pH of NaCl solution is 7.
The NaCl solution means NaCl is dissolved in water. If we see the reaction of NaCl with water if possible, it will give NaOH which is a strong base and HCl which is a strong acid. Both strong acid and strong base will react to give neutral pH of 7.
So, this statement is true.
The second statement is that Copper sulphate gives red colour with universal indicator. In actual, Universal indicators show blue colour if solution is basic in nature, green is solution is neutral and red when solution is acidic. So, as the copper sulphate is acidic, it gives red colour with universal indicator.
Thus, this statement is also true.
The third statement says that Degreasing of metals can be done with ${H_2}S{O_4}$.
Degreasing is the process of removal of oil and stain from metal. The Sodium hydroxide is used for degreasing. So, this statement is false.

Thus, the option b.) is correct.

Note:
It must be noted that when a strong acid reacts with a strong base, it gives salt and water and the product is neutral. In the first statement, the sodium hydroxide can not react with water to give acid and base but if it happens, then both will react to form sodium hydroxide and water.