pH and dissolution Soil chemists have commonly used the following equation for e
ID: 995731 • Letter: P
Question
pH and dissolution
Soil chemists have commonly used the following equation for estimating the [Ca^2+] of soil water: log[Ca^2+] +2 pH = constant - log P_co2 As an aquatic chemist, express the constant term above in terms of known OS 120 Aquatic Chemistry S16 - Problem Set #4 - Due: April 28^th (Thursday) equilibrium constants and calculate its value. Now, estimate the [Ca^2+] you would expect at pH=7 and P_co2 = 10^-2.5 atm. The concentration of CO_2 in the "air" is higher in soils than it is in the regular atmosphere because there is so much respiration (exhaling) going on in soils. Under what conditions does this equation hold true?Explanation / Answer
From given information;
Log [Ca2+] + 2 pH = constant - Log PCO2; Log [Ca2+] - 2 Log [H+] = constant - Log PCO2 ;
Log [Ca2+] - 2 Log [H+] + Log PCO2 =constant ; [Ca2+]PCO2 /[H+]2 =constant' ; K=[Ca2+]PCO2 /[H+]2
if all the values of concentration is known we can calculate the equilibrium constant.
b) from the equation Log [Ca2+] + 2 pH = constant - Log PCO2 ;
Log [Ca2+] + 2 x7 = constant - Log 10-2.5 ; Log [Ca2+] + 14 = constant + 2.5 ; Log [Ca2+]= constant - 11.5.
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