Question

Which equivalence factor set should you use to convert from 4.23 x 1012 atoms of Ca to grams of Ca?

A) (1 mol Ca/6.02 x 1023 atoms Ca)(40.08 g Ca/1 mol Ca)
B) (1 mol Ca/4.23 x 1012 atoms Ca)(40.08 g Ca/1 mol Ca)
C) (4.23 x 1012 atoms Ca/1 mol Ca)(1 mol Ca/40.08 g Ca)
D) 4.23 x 1012 atoms Ca/6.02 x 1023 atoms Ca)(40.08 g Ca)

Answer 1

Answer:

`(4.23 * 10^(12) atoms Ca)/(6.02 * 10^(23) atoms Ca)` * 40.08 g Ca

Step-by-step explanation:
1- One mole of any substance contains Avogadro's number of atoms. Avogadro's number = 6.02 * 10²³
To get the number of moles is 4.23 * 10¹² atoms, we will use cross multiplication as follows:
1 mole .................> 6.02 * 10²³ atoms
x moles ................> 4.23 * 10¹²
x = (4.23 * 10¹² atoms Ca) / (6.02 * 10²³ atoms Ca) moles

2- Number of moles can be calculated as follows:
number of moles = mass / molar mass
We know that the molar mass of Ca = 40.08 g/mol, therefore:
number of moles of Ca = mass / 40.08
This means that:
mass of Ca = number of moles of Ca * 40.08

Substitute with the number of moles (x) calculated in part 1 in the above equation to get the mass as follows:
mass of Ca =
`(4.23 * 10^(12) atoms Ca)/(6.02 * 10^(23) atoms Ca)` * 40.08 g Ca

Hope this helps :)