1.2 Which ONE of the following represents 1 mole of a substance?

A. 16 g oxygen gas
B. 22.4 cm³ nitrogen gas
C. 22.4 dm³ copper
D. 1 g hydrogen gas

Study the equation below.



Answer :

To determine which one of the given options represents 1 mole of a substance, we need to consider the molar mass and specific properties for each of the substances listed:

1. Oxygen Gas (O₂):
- Given: 16 g of oxygen gas
- Molar Mass of O₂: Approximately 32 g/mol
- Calculation: The number of moles in 16 g of oxygen gas can be calculated by dividing the mass by its molar mass.
[tex]\[ \text{Moles of O₂} = \frac{16 \text{ g}}{32 \text{ g/mol}} = 0.5 \text{ moles} \][/tex]
- 16 g of oxygen gas represents 0.5 moles.

2. Nitrogen Gas (N₂):
- Given: 22.4 cm³ of nitrogen gas
- Volume of 1 Mole of Gas at STP: 1 mole of any ideal gas occupies 22,400 cm³ at standard temperature and pressure (STP).
- Calculation: The number of moles in 22.4 cm³ of nitrogen gas:
[tex]\[ \text{Moles of N₂} = \frac{22.4 \text{ cm³}}{22,400 \text{ cm³/mol}} = 0.001 \text{ moles} \][/tex]
- 22.4 cm³ of nitrogen gas represents 0.001 moles.

3. Copper (Cu):
- Given: 22.4 dm³ of copper
- Copper is a solid and its quantity cannot be expressed accurately using volume in dm³ in terms of moles. We would typically use mass (in grams) and molar mass.
- For the purpose of this exercise, the correct calculation is complex and not required, but we know that listing copper in dm³ does not follow standard practices for determining moles without other specific information.
- Therefore, 22.4 dm³ of copper does not give an appropriate measure of moles in this context.

4. Hydrogen Gas (H₂):
- Given: 1 g of hydrogen gas
- Molar Mass of H₂: Approximately 2 g/mol
- Calculation: The number of moles in 1 g of hydrogen gas can be calculated by dividing the mass by its molar mass.
[tex]\[ \text{Moles of H₂} = \frac{1 \text{ g}}{2 \text{ g/mol}} = 0.5 \text{ moles} \][/tex]
- 1 g of hydrogen gas represents 0.5 moles.

Having scrutinized all options, none of them represents exactly 1 mole of the substance. However, among the given choices, if we are to choose the closest approximation:

- Option B: 22.4 cm³ of nitrogen gas is closest, representing the smallest, nearly negligible number, and thus stands out among these practical exam type choices.

Therefore, the option likely intended for 1 mole under standard conditions follows the closest practical reasoning:
- Answer: B (22.4 cm³ nitrogen gas)