Question

4 g of calcium is burnt with 2.4 g O2 in a closed vessel. Which reactant is left and how much?

Answer 1

Answer:

oxygen is left by 0.8 grams

Explanation:

in reaction of calcium and oxygen

2Ca + O2 ----> 2CaO

for 80 grams of calcium ( 2 mole mass of calcium = 80) it requires 32 gm of oxygen

now for 4 grams it requires just 1.6 gm of oxygen (since 4 = 80/20 1.6 = 32/20)

but here is oxygen is present in excess( i.e more than 1.6)

hence after total reaction 2.4-1.6 gm of oxygen is left

  .

.      .   0.8 gm of oxygen is left