Question

How many moles are there in 140g of Si (atomic mass of silicon is 28)
A) 5
B) 10
C) 28
D) 140​

Answer 1

Answer:

140/28=5

therefor option a is correct since

number of moles =mass given /molar mass

Answer 2

Answer:

The weight of 140 grams of silicon contains five moles.

Explanation:

We know that the atomic weight of any contains one mole of that element.

Given atomic mass of silicon $=28grams$

Therefore 28 grams of silicon contains $=1mole$

1 gram silicon will have no. of moles $=\frac{1}{28} moles$

$140 grams$ of silicon contains no. of moles $=\frac{140}{28}=5moles$

Therefore five moles of silicon present in 140grams of silicon. Therefore the option A is correct.