GRE Subject Test: Chemistry : pH
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Example Questions
Example Question #41 : Acid Base Chemistry
What is the pH of a solution with a pOH of 
The equation that expresses the relationship between pH and pOH is:
Plugging the pOH given into the equation above gives:
Rearranging this expression gives:
Therefore, the pH of a solution with a pOH of
Example Question #21 : Acids And Bases
HCN dissociates based on the following reaction.
The Ka for hydrogen cyanide is 
Since HCN is a weak acid, we must use the equilibrium equation.
Because the HCN dissociates in solution, we expect the concentrations of protons and cyanide ions to increase, while the concentration of HCN will decrease. After determining the molarity of the solution, we can set up the equation below, using X as the amount of moles that dissociate.
Because X is small, we can neglect its impact in the denominator.
Since X is the concentration of protons in the solution, we can calculate the pH by using the equation 
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