To determine how many molecules of carbon dioxide (CO₂) are present in a 17-gram sample, we first need to calculate the molar mass of CO₂.
The molar mass of CO₂ can be calculated as follows:
- The molar mass of carbon (C) is 12.01 g/mol.
- The molar mass of oxygen (O) is 16.00 g/mol.
Since CO₂ has one carbon atom and two oxygen atoms, its molar mass is: \[ \text{Molar mass of CO₂} = 12.01 , \text{g/mol} + 2 \times 16.00 , \text{g/mol} = 12.01 , \text{g/mol} + 32.00 , \text{g/mol} = 44.01 , \text{g/mol} \]
Next, we calculate the number of moles in the 17-gram sample of CO₂: \[ \text{Number of moles} = \frac{\text{mass}}{\text{molar mass}} = \frac{17 , \text{g}}{44.01 , \text{g/mol}} \approx 0.3863 , \text{mol} \]
To find the number of molecules, we use Avogadro's number, which is approximately \(6.022 \times 10^{23}\) molecules/mol: \[ \text{Number of molecules} = \text{Number of moles} \times \text{Avogadro's number} = 0.3863 , \text{mol} \times 6.022 \times 10^{23} , \text{molecules/mol} \approx 2.32 \times 10^{23} , \text{molecules} \]
Therefore, rounding to three significant figures, the number of molecules of carbon dioxide in a 17-gram sample is approximately: \[ \boxed{2.326 \times 10^{23}} \]