Question

What is the mass of Cl in 21 g of NaCl?

Answer 1

12.78g

Explanation:

21g of `NaCl` is equivalent to 0.36mol.

`Na` (atomic mass = 23 g/mol), `Cl` (atomic mass = 35.5g/mol)

Mole = `("Atomic Mass") ("Molar Mass")`

Total molar mass of `NaCl` = 23 + 35.5 = 58.5 g/mol

Mole = `21 cancel g NaCl` x `"1 mol"/ (58.5 cancel g) NaCl` = 0.36 mol NaCl

1 mol of NaCl consists of 1 mol of Na ion and 1 mol of Cl ion

or

`NaCl` `rarr` `Na^+` + `Cl^-`

Therefore, 0.36mol of NaCl is equal to 0.36mol of Cl.

Mass of Cl = (Mole `Cl`) (Atomic Mass `Cl`)

Mass of Cl = `0.36 "mol Cl"` x `"35 g"/ (1 cancel "mol") Cl`

Mass of Cl = 12.78g `Cl`