Question

Calculate the amount of heat (in kJ) released when 18.5 g or calcium hydroxide is formed. The molar mass of calcium hydroxide is 74.09g

CaO(s) + H2O(I) —> Ca(OH)2(s) + 65.2 kJ

A. 16.3 kJ
B 260.8 kJ
C 130.4 kJ
D 4.18 kJ

Answer 1

16.23 kj

Step-by-step explanation:

Given data:

Mass of calcium hydroxide formed = 18.5 g

Molar mass of calcium hydroxide = 74.09 g/mol

Energy released = ?

Solution:

Chemical equation:

CaO + H₂O → Ca(OH)₂ + 65.2 Kj

Number of moles of Ca(OH)₂:

Number of moles = mass/ molar mass

Number of moles = 18.5 g/ 74.09 g/mol

Number of moles = 0.249 mol

when one mole of Ca(OH)₂ formed 65.2 Kj energy is released.

When 0.249 moles formed energy released is,

0.249 × 65.2 kj = 16.23 kj