how many moles are in 20 grams of ca (calcium)?

Answer:

D. 0.5

Explanation:

Step1: Recall molar - mass formula

The formula to calculate the number of moles $n$ is $n=\frac{m}{M}$, where $m$ is the mass in grams and $M$ is the molar mass in g/mol.

Step2: Find the molar mass of calcium

The molar mass of calcium ($Ca$) is approximately $40\ g/mol$ from the periodic table.

Step3: Calculate the number of moles

Given $m = 20\ g$ and $M=40\ g/mol$, substitute into the formula: $n=\frac{20\ g}{40\ g/mol}=0.5\ mol$.