Respuesta :
Explanation:
It is known that the density of water is 1 kg/L which is also equal to 1000 g/L. And, relation between mass, density and volume is as follows.
Density = [tex]\frac{mass}{volume}[/tex]
or, mass = Density × volume
Hence, putting the given values into the above formula as follows.
mass = Density × volume
= 1000 g/L × 1.20 L
= 1200 g
Also, we are given that concentration of As = 10 ppb = [tex]\frac{10}{10^{9}}[/tex]
Mass of As = concentration x mass of water
= [tex]\frac{10}{10^{9}} \times 1200[/tex]
= [tex]1.2 x 10^(-5) g [/tex]
Therefore, moles of [tex]Na_{3}AsO_{4}[/tex] are as follows.
moles of As = [tex]\frac{mass}{\text{molar mass of As}}[/tex]
= [tex]\frac{1.2 x 10^(-5)}{74.92}[/tex]
= [tex]1.601 \times 10^(-7)[/tex] mol
Hence, calculate the mass of [tex]Na_{3}AsO_{4}[/tex] as follows.
Mass = moles x molar mass of [tex]Na_{3}AsO_{4}[/tex]
= [tex]1.601 \times 10^(-7) \times 207.89 [/tex]
= [tex]332.83 \times 10^{-7}[/tex]
= [tex]3.32 \times 10^(-5) g[/tex]
Thus, we can conclude that mass of given sodium arsenate is [tex]3.32 \times 10^(-5) g[/tex].
