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Question
What weight of oxygen gas will contain the same number of molecules as 56 g of nitrogen gas ?
(O = 16 u ; N = 14 u)
Solution
Mass of nitrogen gas = 56g
We know that equal moles of all substances contain equal number of molecules. (1 mole of all substances contains 6.022 × 1023 molecules).
The first step will be to convert 56g nitrogen gas into moles.
1 mole nitrogen gas N2 = 28g
28g nitrogen = 1 mole
56g nitrogen = 2 moles
Since, equal moles of all substances contain equal number of molecules, 2 moles of nitrogen will have the same number of molecules as 2 moles of oxygen.
The next step will be to find the mass of 2 moles of oxygen in grams.
1 mole of oxygen = 32g
2 moles of oxygen = 32 × 2 = 64g
Hence, 64g oxygen will contain the same number of molecules as 56g nitrogen gas.
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