Question

calculate the number of atoms in a 5.39×10³ g sample of lithium. number of atoms:

Explanation:

Step1: Find molar mass of lithium

The molar mass of lithium (Li) is approximately 6.94 g/mol.

Step2: Calculate number of moles

The number of moles $n$ is calculated by the formula $n=\frac{m}{M}$, where $m$ is the mass and $M$ is the molar mass. Given $m = 5.39\times10^{3}$ g and $M=6.94$ g/mol, so $n=\frac{5.39\times 10^{3}\text{ g}}{6.94\text{ g/mol}}\approx776.66$ mol.

Step3: Use Avogadro's number

Avogadro's number $N_{A}=6.022\times 10^{23}$ atoms/mol. The number of atoms $N$ is given by $N = n\times N_{A}$. Substituting $n = 776.66$ mol and $N_{A}=6.022\times 10^{23}$ atoms/mol, we get $N=776.66\text{ mol}\times6.022\times 10^{23}\text{ atoms/mol}\approx4.687\times 10^{26}$ atoms.

Answer:

$4.687\times 10^{26}$