WAEC Chemistry 2014 Paper

Concept:An alkali is a substance whose $pH$ value is greater than $7$.Explanation:The $pH$ scale tells us whether a substance is acidic, neutral, or alkaline.If $pH < 7$, the substance is acidic.If $pH = 7$, the substance is neutral.If $pH > 7$, the substance is alkaline.Lime has $pH = 2.4$, which is less than $7$, so it is acidic.Banana has $pH = 4.6$, which is less than $7$, so it is acidic.Distilled water has $pH = 7.0$, which is neutral.Milk of magnesia has $pH = 10.5$, which is greater than $7$.Hence, milk of magnesia is the alkali among the given options.Answer:D. Milk of magnesia with $pH = 10.5$