Question

20% ringChemistry onate Item 1 > A Review Constants Periodic Table Equilibrium constants at 25°C are listed in the table below Substance K Value of K. CaCO3 Ksp 4.5 x 10-9 Kai 4.3 x 10-7 H2CO3 K-2 5.6 x 10-11 Part A What is the molar solubility of marble (i.e., Ca2+ in a saturated solution) in normal rainwater, for which pH = 5.60? Express your answer to two significant figures and include the appropriate units.

Answer 1

-solution The molar solubility of marble in rain water is expressed by the following equation cacaz.(s) + H*) = cazcaq) + HCoz.caq) This equation occurs in the following way caco3(aq) = ca caq) + cordags_ksp= 4.5x109 coszcaq + Heag) Hooz.can) - The overall equation becomes CaCO3 (5) + Htay) = Caltagy + HCozcan) _ - Kekse x Kaz K = 4.5 xjög x 117857 x 10° = 80.357 Now, calcrelate. [H+J; Given pH = 5.60 pH = -logi (HJ 5.60 er dog, o CHA ] log CHJ = -5.60 TH] = Antilog C6.40) Eht] 32.5 x 16 we known that [cat] = [HCog] = x K = [ca?t] [ H Cog ht

where, k= 800357 [A+] = 2.58 10 6 [ca²+] = [HCog] =0 80.357 = [x] ² 2.5xlob '. x2 = 30.357 x 2.5 X10 is X = V 80.357 X 2.5. X. 106 GEO = 0.01672 O This (ca2+] = 0.0142 M [ca2+] = 1.48102 m. (2 sig. fig)