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Aspirin (acetyl salicyclic acid, molar mass `180 g "mol"^(-1)`) used as analgesic has `pK_(a)` value of 2. Two tablets of aspirin each weighing 90 mg are dissolved in 100 mL of water. The pH of the solution isA. 0.5B. `1.0`C. `2.0`D. `4.0` |
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Answer» Correct Answer - C Aspirin is a weak acid. Hence, its pH is given by `pH=(1)/(2)[pK_(a)-log c]` Here, `c=2xx0.09 g "in " 100 mL = 1.8 g L^(-1)` `=(1.8)/(180)M=0.01 M` `:. pH=(1)/(2) [2-log 0.01]=(1)/(2)[2-(-2)]=2` |
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