Answer to Question #249702 in General Chemistry for Ian

Question

a 0.910 g sample of magnesium was reacted with oxygen to form 1.510 g of magnesium oxide.how much magnesium is needed to produce 0.850 g of magnesium oxide? how much magnesium and oxygen are needed to produce exactly 2.55 of magnesium oxide

Answer 1

In the first case we can calculate the Mass of oxygen used =1.510g-0.910g

For the second question;

$2Mg+O_2\to 2MgO$

now moles of magnesium oxide $=\frac{0.850}{2(24+16)}=0.0106$

mole ratio; $2Mg:2MgO=2:2=1:1$

moles of Mg=0.0106

mass of magnesium$=48\times 0.0106=0.5088g$

For the next question;

$2Mg+O_2\to 2MgO$

mass of magnesium oxide $=\frac{2.55}{2(24+16)}=0.031875$

mole ratio $2MgO:2Mg=2:2=1:1$

mass of Mg $=2\times 24\times 0.031875=1.53g$

mass of oxygen=2.55g-1.53g=1.02g