[appleseed]

what is the mass of zinc with the same number of atoms as there are hydroxide ions in 12.2g of magnesium hydroxide Mg(OH)2

the answer should be 27.3g

please could you give me the working out

thannkyou!!

[Astrokel]

Hi appleseed, you need to show some attempt first. Always start working with moles!

[appleseed]

Hiya!
so here goes:
composition of (OH)2 in Mg(OH)2 is  34/58.31

hence the mass of (OH)2 in 12.2g is 12.2 x 34/58.31 = 7.11g

then i am stuck!!

help help please

[sjb]

Hiya!
so here goes:
composition of (OH)2 in Mg(OH)2 is  34/58.31

hence the mass of (OH)2 in 12.2g is 12.2 x 34/58.31 = 7.11g

then i am stuck!!

help help please

7.11g is how many moles of hydroxide? So how many moles of zinc do you need? So what mass of zinc do you need?