Problem: Calculate the [H3O+] of the following polyprotic acid solution: 0.145M H3C6H5O7.Calculate the pH of this solution.

FREE Expert Solution

Since we’re dealing with a weak acid, we will have to create an ICE chart to determine the equilibrium concentration of each species:

K=productsreactants

Solids and liquids are not included in the expression


K1=H2C6H5O7-H3O+H3C6H5O78.4×10-4=xx0.145-x8.4×10-4=x2(0.145-x)

Check if the x in the denominator can be ignored

[H3C6H5O7]iKa=0.145 M8.4×10-4=173<500

since 172 < 500, x in the denominator cannot be ignored

{8.4×10-4=x2(0.145-x)}(0.145-x)(8.4×10-4)(0.145-x)=x21.218×10-4-(8.4×10-4)x=x2x2+(8.4×10-4)x-1.218×10-4=0

Solve for x using the quadratic formula:

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Problem Details

Calculate the [H3O+] of the following polyprotic acid solution: 0.145M H3C6H5O7.

Calculate the pH of this solution.

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