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The volume occupied by 2.8 g of N2 at STP______________________?

Correct answer: A. 2.24 dm3

  • A. 2.24 dm3
  • B. 22.4 dm3
  • C. 1.12 dm3
  • D. 112 dm3

Explanation

The molar mass of N2 is 2 x 14 g mol^-1 = 28 g mol^-1, so 2.8 g represents 2.8 g / 28 g mol^-1 = 0.10 mol. At STP, 1 mol of an ideal gas occupies 22.4 dm3, giving 0.10 mol x 22.4 dm3 mol^-1 = 2.24 dm3. Students may choose b by using the molar volume without first multiplying by the 0.10 mol present.

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About Standard Temperature and Pressure

Standard temperature and pressure provide reference conditions for gas calculations: 0°C or 273 K and, in the usual school convention, 1 atm pressure. Questions use these conditions to relate pressure, volume, temperature and amount of gas, including the molar volume of an ideal gas, about 22.4 dm³.

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