# Question #57b25

Aug 20, 2017

Your answer is entirely reasonable. However your answer has too many significant digits 90.4 grams of $M {g}_{2} S i$ has only three significant digits so your answer can have only 3 significant digits
None of the answer given seem to be correct.

#### Explanation:

First find the number of moles of$M {g}_{2} S i$in 90.4 grams of $M {g}_{2} S i$

$2 \times M g = 2 \times 24 = 48$
$1 \times S i = 1 \times 28 = 28$ adding them gives

$48 + 28 = 76 \frac{g}{m} M {g}_{2} S i$

$\frac{90.4}{76} = 1.19 m .$

1 mole of $M {g}_{2} S i$ = 1 mole of $S i {H}_{4}$

so 1.19 moles of $M {g}_{2} S i$ = 1.19 moles $S i {H}_{4}$

$1 S i = 1 \times 28 = 28$
$4 H = 4 \times 1 = 4$

adding them gives 32 g/m $S i {H}_{4}$

$1.19 \times 32 \frac{g}{m} = 38.1 g S i {H}_{4}$