Questions 7,8 and 9 please. The correct answer is circled please just show work

Question

Questions 7,8 and 9 please.

The correct answer is circled please just show work displaying how to arrive at the correct answer.

Thanks!

(7). A 0.1594-g sample of an organic compound was burned in a stream of oxygen, and the CO2 (molar mass = 44.01 g/mol) produced was collected in a solution of barium hydroxide (Ba(OH)2). Calculate the percentage of carbon (molar mass = 12.01 g/mol) in the sample, if 0.6347 g of BaCO3 (molar mass = 197.34 g/mol) was formed. (a). 24.23% (b). 2.02% (e). 0.32% (d). 88.80% (e).7.39% (8). The solubility of AgCl in an aqueous solution is 1.00 x 105 M. Will the solubility of AgCl in 0.1 M NaNO; be (a greater than 1.00 x 10-M (d). No enough information given (b). equal to 1.00 x 10M (e). none of the above (C). Less than 1.00 x 10M (9). How many moles of NaOH must you add to 0.500 mol of benzoic acid (C6H3COOH ) to make 1.00 L of a pH 4.20 buffer (pKa = 4.20). (a). 1.000 (b). 0.333 0.250 (d).0.170 (e). no enough information given

Explanation / Answer

7) No of mol of BaCo3 formed = 0.6347/197.34 = 0.00322 mol

   1 mol BaCO3 = 1 mol CO2

no of mol of CO2 formed = 0.00322 mol

mass of C in CO2 = 0.00322*12 = 0.03864 g

% of C in sample = 0.03864/0.1594*100 = 24.24%

answer: a

8) AgCl(s) + NaNO3(aq) -----> NaCl(aq) + AgNO3(aq)

so that, solubility of AgCl increases.

answer: a

9)

pH of acidic buffer = pka + log(C6H5COONa/C6H5COOH)

      4.2 = 4.2 + log(x/(0.5-x))

x = 0.25

No of mol of NaOH = c6h5coona = x = 0.25 mol

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