Question

40g of calcium metal is burned in oxygen of air to form calcium oxide.
a. Write the chemical equation
b. Find the mass of the calcium oxide
c. Find the volume of the required air if the volume of oxygen is 1/5 times of the volume of air.
Given: Ca = 40, C = 12, O = 16, N = 14, H = 1, At STP: 32 of O2 contain volume 22.4L

Answer 1

Given info : 40g of calcium metal is burnt in oxygen of air to form calcium oxide.

To find :

(a) write the chemical equation

(b) find the mass of the calcium oxide

(c) find the volume of the required air if the volume of oxygen is 1/5 times of the volume of air.

solution : (a) 2Ca + O₂ = 2CaO

(b) in reaction, you see 2 mole of CaO is formed by 2 mole of calcium metal.

so, no of moles of CaO = no of moles of Ca

⇒mass of CaO/molar mass of CaO = mass of Ca/atomic mass of Ca

⇒ mass of CaO/56 = 40/40 = 1

⇒mass of CaO = 56 g

(c) From reaction,

no of moles of oxygen = 1/2 no of moles of Ca

= 1/2 × 1 = 0.5 mol

volume of 1 mole oxygen at STP is 22.4 L

so, volume of 0.5 mol of oxygen at STP is 11.2 L

now volume of air = 5 × volume of oxygen

= 5 × 11.2 L

= 56 L