Calculate the equilibrium constant for OBr if a 0.1M solution of NaOBr has a pH

Question

Calculate the equilibrium constant for OBr if a 0.1M solution of NaOBr has a pH of 10.85. Write the ionic equation of salt hydrolysis. Based on this equation, classify the salt as acidic, basic or neutral. What is the pH of a buffer that is 0.120 M in lactic acid. HC_3H_3 O_3, and 0.100M in sodium lactate, NaC_3H_3O_3? For lactic acid, k_a = 1.4 times 10^study the thermo dynamics of KNO_3 dissolving in water (including trends observed as the total volume of solution increases) a) Is the process spontaneous or non-spontaneous? Briefly explain b) what happens to the delta s as the molar concentration of dissolved ions decreases? C) Is the dissolution process exothermic or endothermic ? briefly explain Calculate the molar mass of an unknown substance if a solution containing 158 g of unknown is 15 g of water freezes at -1.25 degree C. K_ for water = 1.86 degree C/m

Explanation / Answer

Question 1.

find K for OBr- given

NaOBr --> 10.85

pOH = 14-pH = 14-10.85 = 3.15

[OH-] = 10^-pOH = 10^-3.15 = 0.0007079 M

by stoichiometry:

OBr- + H2OI <--> HOBr + OH-

[OH-] = [HOBR] = 0.0007079

[OBr-] = 0.1-0.0007079 = 0.0992921 M

substitute

Kb = [HOBR][OH-]/[OBr-]

Kb = (0.0007079)(0.0007079)/(0.0992921 ) = 0.00000504695

Ka = Kw/Kb = (10^-14)/(0.00000504695) = 1.9813*10^-9

the salt is clearly BASIC

since pH >A 7

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