Question

Determine the number of atoms in 75.0 grams of sodium, Na.

Answer 1

Answer: 1.96×10²⁴

Step-by-step explanation:

Since we are given the grams (mass) of Na and are being asked to find the atoms (particles) of Na, we can use stoichiometry with 2 ratios to identify the number of atoms in sodium.

We are going from grams → moles → atoms in this question

First, set up your first ratio. Since we are going from grams to moles in this first ratio, the first ratio would be 1 mole divided by the molar mass of the substance.

`((75.0 g Na)/(1))`
`((1 mol)/(molar mass))`

The molar mass of sodium (Na) is 23 g/mol or amu

`((75.0 g Na)/(1))`
`((1 mol)/(23g/mol))`

= 3.26 mol Na (you don't have to round this early, but for the sake of simplicity, I am rounding it to the appropriate number of significant figures)

Now we can convert moles to atoms. This ratio will be Avogadro's number divided by 1 mole.

`((3.26mol)/(1) )`
`((6.02*10^(23) )/(1mol) )`

= 1.96252×10²⁴ atoms of Na

Since the information we were given (75.0 g of Na) has 3 significant figures, round 1.96252 to 3 sig figs.

= 1.96×10²⁴ atoms of Na