Question

what conversion factor should be used to convert 2.48 moles of ca to grams of ca?
2.48 moles ca x (\frac{1 \text{ mole } ca}{6.02\times10^{23} \text{ particles } ca})
2.48 moles ca x (\frac{6.02\times10^{23} \text{ particles } ca}{1 \text{ mole } ca})
2.48 moles ca x (\frac{40.078 \text{ grams } ca}{1 \text{ mole } ca})
2.48 moles ca x (\frac{1 \text{ mole } ca}{40.078 \text{ grams } ca})

Explanation:

Step1: Recall molar - mass concept

To convert moles to grams, we use the molar mass of the substance as the conversion factor. The molar mass of calcium (Ca) is approximately 40.078 g/mol. This means that 1 mole of Ca has a mass of 40.078 grams.

Step2: Analyze conversion - factor requirements

We want to convert 2.48 moles of Ca to grams of Ca. The correct conversion factor should have grams in the numerator and moles in the denominator so that the moles unit cancels out.

Answer:

$2.48\text{ moles Ca}\times\frac{40.078\text{ grams Ca}}{1\text{ mole Ca}}$ (The third - option you provided has an incorrect value in the numerator, and the correct one is not among the given options exactly, but the correct form of the conversion factor is $\frac{\text{molar mass of Ca (in grams)}}{1\text{ mole Ca}}$, where the molar mass of Ca is 40.078 g/mol)