Which of the following solution(s) have pH between 6 and 7 ? 1. 2 × 10-6 M NaOH 2. 2 × 10-6 M HCl 3. 10-8 M HCl 4. 10-13 M NaOH

Question

Which of the following solution(s) have pH between 6 and 7 ? 1. 2 × 10-6 M NaOH 2. 2 × 10-6 M HCl 3. 10-8 M HCl 4. 10-13 M NaOH (A) 1, 2 (B) 2, 3 (C) 3, 4 (D) 2, 3, 4

Tardigrade Admin · Accepted Answer

pH of 10-8 M HCl is not 8 but it is less than 7 because in this case contribution of H +from water is not neglected. Total H +=10-8 (from acid) +10-7 (from water) =10-8(1+10) =11 × 10-8 M pH =- log [ H +]=- log [11 × 10-8] =-[ log 11+ log 10-8] =-[1.0414-8] =6.9586 ≃ 6.96

Q. Which of the following solution(s) have pH between 6 and 7? 1. 2×10−6MNaOH 2. 2×10−6MHCl 3. 10−8MHCl 4. 10−13MNaOH

1, 2

2, 3

3, 4

2, 3, 4

pH of 10−8MHCl is not 8 but it is less than 7 because in this case contribution of H+from water is not neglected. Total H+=10−8 (from acid) +10−7 (from water) =10−8(1+10) =11×10−8M pH=−log[H+]=−log[11×10−8] =−[log11+log10−8] =−[1.0414−8] =6.9586≃6.96

Q. Which of the following solution(s) have $p H$ between $6$ and $7 ?$
1. $2 \times 1 0^{- 6} M N a O H$
2. $2 \times 1 0^{- 6} M H Cl$
3. $1 0^{- 8} M H Cl$
4. $1 0^{- 13} M N a O H$