Question

1. Strontium hydroxide is used in refining beet sugar and separating cyrstallizable sugar from molasses. It is commonly found as the octahydrate, Sr(OH)₂.8H₂O. If a solution is prepared by dissolving 0.45 grams of this compound in sufficient water to make 100 ml of solution, determine the [H⁺], the [OH^-], the pH and the pOH of the solution.

2. Ethylamine (C₂H₅NH₂) is a flammable liquid with an ammonia-like odor that is miscible with water. It is irritating to skin, mucous membranes and to the respiratory tract. The density of ethylamine is 0.689 g/ml. If the Ka of this C2H5 NH2 is 2 x 10^-11, determine the [H⁺], the [OH^-], the pH and the pOH of a solution prepared by dissolving 25.0 ml of this compound in 500 ml of solution.

3. Phenylpropionic acid, C₉H₁₀O₂, also known as hydrocinnamic acid , is a white crystalline solid with a sweet floral scent at room temperature. It has a wide variety of uses including cosmetics, food additives, and pharmaceuticals. If a 0.075 M solution of this acid has a pH of 2.89, determine the Ka for the acid.

Answer 1

roak 100 DOO Vinml molarmow 1) molarity of Solo192.840 = E 0145 & 1000 265.63" TOO E O DIGAM COH ? = 2*0.0169 = 0.0338 M [44] [ori] = 10x1604 → [H*] = 1.Dx 16 0.0338 poh E-log (ott) PH=14 pol E-log (0.0338) | E14-4047 1:47 IF 12.53. -13 F2.96x 10 M 2) density = mane 45.08 max = dersityx volume → 0.689x25 17.225g molaritye 1.335 0764 m SH5NH, + 40 = Shemaling initial 0.764 *x + change (0.764-4) * x equilibrium k, - ни, Поu 7 C2H5NH2] 15.0x 164 x 0.764-X) X=0.0193M Low' ] = 0.0193 m, [ 445] =10 prox105 .18 x 10 poh e-log(0.0193) phorlog (5:18x16'3) 51071 12:29 karkb=1.0x1014 kb= loxiohh 2x161 + 5.0*104 2 0.0193

3) pH = 2.89 Shpe] = 10 " PH -2.89 10 0.001288 M CI HO O + 40 = Cquqe 2 + H2B At equilibrilem. ka= [cqHqg0] [40] Cahol = 0.075-0.001288 [cat ] -0.0T3T M (0.001288) (0.001288) (0.0937) = 2.25x165