13) Calculate the poll of a solution that contains 2.4 × 10-5 M H30, A) 2.40 B)

Question

13) Calculate the poll of a solution that contains 2.4 × 10-5 M H30, A) 2.40 B) 9.38 C) 4.62 D) 11.60 E) 4.17 at 25°C 14) Determine the [H30 ] in a 0.265 M HCO solution. The Ka of HCO is 2.9 × 10-8. A) 1.1 x 10-10 M B) 7.7 × 10-9 M C)1.3×10-6 M D) 4.9 × 10-4 M E) 88 x 10-5 M 15) Which of the following is a WEAK base? A) NH(CH3)2 B) N2 C) NaOH D) CH2CH2 E) None of the above are weak bases. 16) Which of the following bases is the STRONGEST? The base is followed by its Kb A) (CH3CH2)2NH, 8.6 × 10-4 B) CH3NH2, 4.4 x 10-4 C) C6HsNH2, 4.0 x 10-10 D) NH3, 1.76 × 10-5 E) C$HSN, 1.7 x 10-9 17) Determine the pH of a 0.116 M Ba(OH)2 solution at 25°C. A) 8.62 B) 13.06 C) 13.37 D) 0.63 E) 12.56 18) Which of the following acids is the WEAKEST? The acid is followed by its Ka value. A) HC2H302, 1.8 x 10-5 B) HIO, 2.3 x 10-11 OHBrO2.3x 10.9 DHCIO, 2.9 × 10-8 E) C6HsCO2H, 6.3 x 105 19) Which of the following is not a base? d) C,H&NNH2; c) C2H,COOH a) NHs b) CaHNH

Explanation / Answer

13)

use:
pH = -log [H3O+]
= -log (2.4*10^-5)
= 4.62


POH = 14 - pH
= 14 - 4.62
= 9.38
Answer: B

14)
HClO dissociates as:

HClO          ----->     H+   + ClO-
0.265                 0         0
0.265-x               x         x


Ka = [H+][ClO-]/[HClO]
Ka = x*x/(c-x)
Assuming x can be ignored as compared to c
So, above expression becomes

Ka = x*x/(c)
so, x = sqrt (Ka*c)
x = sqrt ((2.9*10^-8)*0.265) = 8.766*10^-5

since c is much greater than x, our assumption is correct
so, x = 8.766*10^-5 M



so.[H+] = x = 8.8*10^-5 M

Answer: E

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