Answer to Question #191783 in Chemistry for Priyanshi Raturi

Question

A 0.835 sample of hydrated calcium nitrate was heated carefully it has changed completely to the anhydrous form. After heating, the sample mass was recorded as 0.580g. Determine the value of x(must be a whole number)

Answer 1

Solution:

anhydrous form of calcium nitrate = Ca(NO₃)₂ (0.580 g)

hydrated calcium nitrate = Ca(NO₃)₂ ∙ xH₂O (0.835 g)

Therefore,

Mass of xH₂O = 0.835 g - 0.580 g = 0.255 g

The molar mass of Ca(NO₃)₂ is 164.088 g/mol

Therefore,

Moles of Ca(NO₃)₂ = [0.580 g Ca(NO₃)₂] × [1 mol Ca(NO₃)₂ / 164.088 g Ca(NO₃)₂] = 0.00353 mol

Moles of Ca(NO₃)₂ = 0.00353 mol

The molar mass of H₂O is 18.0153 g/mol

Therefore,

Moles of H₂O = [0.255 g H₂O] × [1 mol H₂O / 18.0153 g H₂O] = 0.01415 mol

Moles of H₂O = 0.01415 mol

Ca(NO₃)₂: 0.00353 / 0.00353 = 1

H₂O: 0.01415 / 0.00353 = 4

Thus,

The value of x is 4.

Ca(NO₃)₂ ∙ xH₂O = Ca(NO₃)₂ ∙ 4H₂O

Answer: The value of x is 4