Question

How many formula units of baking soda (sodium bicarbonate) are in 2.60 tsp? (1 tsp ≈ 7.20 g nahco3)?

Answer 1

2.60 x 7.20= 18.72 g NaHCO3

Answer 2

In 1 mole of $NaHCO_{3}$ there are $6.023\times 10^{23}$ formula units of $NaHCO_{3}$.

Since, 1 tsp of $NaHCO_{3}$ is approximately 7.20 g of $NaHCO_{3}$. Mass of 2.60 tsp of $NaHCO_{3}$ can be calculated as follows:

$1 tsp\rightarrow 7.20 g$

Thus,

$2.60 tsp\rightarrow (2.60)(7.20 g)=18.72 g$

Converting mass into number of moles as follows:

$n=\frac{m}{M}$

here, n is number of moles, m is mass and M is molar mass.

Molar mass of $NaHCO_{3}$ is 84 g/mol thus, number of moles will be:

$n=\frac{18.72 g}{84 g/mol}=0.22 mol$

Since, $1 mole\rightarrow 6.023\times 10^{23}formula units$

thus,

$0.22 mol\rightarrow 6.023\times 10^{23}\times 0.22=1.34\times 10^{23}formula units$

Thus, $1.34\times 10^{23}$ formula units of baking soda are in 2.60 tsp.