Stoichiometry - Engineering

Q1:

At room temperature, the product [H+] [OH-] in a solution is 10-14 moles/litre. If, [OH-] = 10-6 moles/litre, then the pH of the solution will be

A 6

B 8

C 10

D 12

ANS:B - 8

The product of the hydrogen ion concentration ([𝐻+][H+]) and the hydroxide ion concentration ([𝑂𝐻−][OH−]) in a solution at 25°C (room temperature) is constant and equal to 10−1410−14 moles per liter, as defined by the ion product of water (𝐾𝑤Kw​): 𝐾𝑤=[𝐻+]×[𝑂𝐻−]=10−14 moles/LKw​=[H+]×[OH−]=10−14moles/L Given that [𝑂𝐻−]=10−6[OH−]=10−6 moles per liter, we can rearrange the equation to solve for [𝐻+][H+]: [𝐻+]=10−14[𝑂𝐻−]=10−1410−6=10−8 moles/L[H+]=[OH−]10−14​=10−610−14​=10−8moles/L Now, to find the pH of the solution, we use the equation: pH=−log⁡[𝐻+]pH=−log[H+] pH=−log⁡(10−8)=−(−8)=8pH=−log(10−8)=−(−8)=8 Therefore, the pH of the solution will be 8. So, the correct option is 8.