Elemrnts Long questions: (28 points) Show 1. Hypochlorous acid HOCI is a weak (a

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Elemrnts Long questions: (28 points) Show 1. Hypochlorous acid HOCI is a weak (a) (2pt) Determine (b) (2pt) Determine the number of mole of NaOH in a 48.0-mL solution (c) (8pt) Determine the pH of the after 30.0 calculation and/or explanation to receive partial credins number of mole of HOCI in the 30.0-ml solution of O.AD-M woO. acid with k 4.0x10.30.0 mL of 0.40-M HOCI is titrasted woith 9. with 0.25 M NDH of 0.25 M NaOH ure at equilibrium after 30.0 ml of 0.40-M HOCI is mixed with 48, 0 mt o2s mL of 0.40-M HoC iS with 48 0 of 025 NaOH. Show your detailed calculation. (d) (4pt) If value (greater than, eq the final solution should haave the we add 15.0 ml of 0.25-M NaOH into 30.0 ml of 0.40-M HOCI, then ual to, or less than) pK,? Explain your choice e) (3pt) Which of the following acids is a stronger acid: (hv choice. pochlorous acid HOCI or perchloric acid HCIO? Explain your a) HCIO b) HOCI d) none of above c) same for both

Explanation / Answer

a) 0.40 M = 0.4 mole/lit, 30 ml solution has = 0.03 L* 0.4 mole/lit, = 0.012 mole HOCl

b) 48 ml of 0.25 M NaOH = 0.25 mole /lit * 0.048 L = 0.012 mole

c) so the mole number of HOCl = mole number of NaOH. Therefore, it is the neutralization point of acid base titration and there sre no excess of proton or hydroxide ion. so, the pH = 7

d)15 ml of 0.25 M NaOH = 0.25 mole /lit * 0.015 L = 0.00375 mole of NaOH neutralize 0.00375 mole of acid to prepared 0.00375 mole of salt. mole of remaining acid = 0.012 mole - 0.00375 mole = 0.00825 mole

now, according to Henderson equation

pH = pKa + log [salt] / [acid]  

the value of log [0.00375/0.00825] = - 0.34

therefore, final value of pH must be lesser than pKa value

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