determine the quantity of moles in 4.21×10²³ formula units of cacl₂

Explanation:

Step1: Recall Avogadro's number

Avogadro's number ($N_A$) is $6.022\times 10^{23}$ formula - units/mol.

Step2: Use the conversion formula

The number of moles ($n$) is given by the formula $n=\frac{N}{N_A}$, where $N$ is the number of formula - units. Here, $N = 4.21\times 10^{23}$ formula - units. So, $n=\frac{4.21\times 10^{23}}{6.022\times 10^{23}}$ mol.

Step3: Calculate the result

$n=\frac{4.21}{6.022}\approx0.70$ mol.

Answer:

$0.70$