Question

Question #6b970

Answer 1

The mass of the magnesium hydroxide present in the tablet is `"1 g"`.

So, you know that each tablet contains 500 mg of magnesium. However, this magnesium is actually a part of magnesium hydroxide, `Mg(OH)_2`.

To see how much magnesium hydroxide you have in every tablet, you must first determine the percentage by mass magnesium has in `Mg(OH)_2`. To do this, use their respective molar masses

`(24.3050cancel("g/mol"))/(58.3197cancel("g/mol")) * 100 = "41.68%"`

This means that you get 41.68 g of magnesium for every 100 g of `Mg(OH)_2`. As a result, 500 mg of magnesium would correspond to

`500 * 10^(-3)cancel("g Mg") * ("100 g "Mg(OH)_2)/(41.68cancel("g Mg")) = "1.199 g "Mg(OH)_2`

Rounded to one sig fig, the number of sig figs given for 500 mg, the answer will be

`m_(Mg(OH)_2) = color(green)("1 g")`