Question

Calculate [H+] for each of the following solutions, and indicate whether the solution is acidic, basic, or neutral.

Answer 1

Answer:

Part A: 10.7.

Part B: 2) the solution is basic.

Part C: 5.9.

Part D: 1) the solution is acidic.

Part E: 8.1.

Part F: 2) the solution is basic.

Explanation:

Part A [OH−]= 4.5×10−4 M . Express your answer using two significant figures.  

∵ [H₃O⁺][OH⁻] = 10⁻¹⁴.

[OH⁻] = 4.5×10⁻⁴ M.

∴ [H₃O⁺] = 10⁻¹⁴/[OH⁻]  = 10⁻¹⁴/(4.5×10⁻⁴  M) = 2.22 × 10⁻¹¹ M.

∵ pH = - log[H₃O⁺]

∴ pH = - log(2.22 × 10⁻¹¹) = 10.65 ≅ 10.7.

Part B 1) the solution is acidic 2) the solution is basic 3) the solution is neutral  

The solution is basic, because the pH is higher than 7.

Part C [OH⁻]= 7.7×10⁻⁹ M . Express your answer using two significant figures.  

∵ [H₃O⁺][OH⁻] = 10⁻¹⁴.

[OH⁻] = 7.7×10⁻⁹ M.

∴ [H₃O⁺] = 10⁻¹⁴/[OH⁻]  = 10⁻¹⁴/(7.7×10⁻⁹ M) = 1.29 × 10⁻⁶ M.

∵ pH = - log[H₃O⁺]

∴ pH = - log(1.29 × 10⁻⁶) = 5.88 ≅ 5.9.

Part D 1) the solution is acidic 2) the solution is basic 3) the solution is neutral  

The solution is acidic, because the pH is lower than 7.

Part E A solution in which [OH−] is 140 times greater than [H+]. Express your answer using two significant figures.  

∵ [H₃O⁺][OH⁻] = 10⁻¹⁴.

∵  [OH⁻] = 140[H₃O⁺]

∴ [H₃O⁺](140[H₃O⁺]) = 10⁻¹⁴.

∴ 140 [H₃O⁺]² = 10⁻¹⁴.

[H₃O⁺]² = 10⁻¹⁴/ 140 = 7.14 x 10⁻¹⁷.

∴ [H₃O⁺] = √(7.14 x 10⁻¹⁷) = 8.45 x 10⁻⁹ M.

∵ pH = - log[H₃O⁺]

∴ pH = - log(8.45 x 10⁻⁹) = 8.07 ≅ 8.1.

Part F 1) the solution is acidic 2) the solution is basic 3) the solution is neutral

The solution is basic, because the pH is higher than 7.