Ionic product of water and the pH scale — NEET & JEE Questions

Question 1 · difficulty L1 · recall

At 25°C, the ionic product of water $K_w=[H^+][OH^-]$ is approximately

• A. $1.0\times10^{-14}$
• B. $1.0\times10^{-7}$
• C. $1.0\times10^{7}$
• D. $14$

Question 2 · difficulty L2 · understanding

At 25°C, a neutral aqueous solution has

• A. $[H^+]=[OH^-]=10^{-7}\,M$
• B. $[H^+]=10^{-14}\,M$
• C. $[OH^-]=1\,M$
• D. $[H^+]=0$

Question 3 · difficulty L2 · understanding

The pH of an aqueous solution is defined as

• A. $-\log_{10}[H^+]$
• B. $\log_{10}[H^+]$
• C. $-\log_{10}[OH^-]$
• D. $[H^+][OH^-]$

Question 4 · difficulty L2 · understanding

At 25°C, pH and pOH are related by

• A. pH + pOH = 14
• B. pH - pOH = 14
• C. pH × pOH = 14
• D. pH = pOH for every solution

Question 5 · difficulty L3 · application

What is the pH of a solution with $[H^+]=1.0\times10^{-3}\,M$?

• A. 3
• B. 7
• C. 11
• D. -3

Question 6 · difficulty L3 · application

What is the pOH of a solution with $[OH^-]=1.0\times10^{-4}\,M$?

• A. 4
• B. 10
• C. 14
• D. -4

Question 7 · difficulty L3 · application

At 25°C, a solution has pOH = 3. What is its pH?

• A. 3
• B. 7
• C. 11
• D. 17

Question 8 · difficulty L3 · application

At 25°C, if $[H^+]=1.0\times10^{-5}\,M$, what is $[OH^-]$?

• A. $1.0\times10^{-9}\,M$
• B. $1.0\times10^{-5}\,M$
• C. $1.0\times10^{-14}\,M$
• D. $1.0\times10^{-19}\,M$

Question 9 · difficulty L4 · application

A solution has pH 2. Compared with a solution of pH 5, its hydrogen-ion concentration is

• A. 1000 times greater
• B. 3 times greater
• C. 100 times greater
• D. 1000 times smaller

Question 10 · difficulty L4 · application

At 25°C, a strong base solution has $[OH^-]=2.0\times10^{-3}\,M$. Its pOH is closest to

• A. 2.70
• B. 3.00
• C. 11.30
• D. 0.30