WAEC - Chemistry (2024 - No. 32)
The volume of 22g of CO\(_2\) at stp is equivalent to [C =12, O =16, molar volume at stp = 22.4 dm\(^3\) ]
22.0 dm\(^3\)
22.4 dm\(^3\)
11.2 dm\(^3\)
5.6 dm\(^3\)
Explanation
Given:
m = 22g
M.V = 22.4dm\(^3\)
V = ?
First, calculate the number of moles n, by dividing mass of CO\(_2\) by the molar mass of CO\(_2\), since n = \(\frac{mass}{Molar mass}\)
Molar mass of CO\(_2\) = 12 + (2 x 16) = 44g/mol
So, n = \(\frac{mass}{Molar mass}\)
n = \(\frac{22}{44}\) = 0.5 mole
Also recall that number of moles of gases, n = \(\frac{Volume}{Molar Volume}\)
n = \(\frac{V}{M.V}\)
0.5 = \(\frac{V}{22.4}\)
V = 0.5 X 22.4
V = 11.2 dm\(^3\)
Alternatively,
Given the mass of CO\(_2\) = 22g
Molar mass of CO\(_2\) = 12 + (16X2) = 44g
number of moles, n = \(\frac{m}{M}\) = \(\frac{22}{44}\) = 0.5 mole.
If 1 mole of CO\(_2\) = 22.4dm\(^3\)
0.5 mole of CO\(_2\) = X dm\(^3\)
X = 0.5 x 22.4 = 11.2 dm\(^3\)
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