Question

While Josh was cleaning out the stockroom, he finds a jar labeled "1.56 moles of "cobalt nitrate". Since stock convention was not used, you do not know the oxidation number of the cobalt. You mass the contents and find a mass of 2.85x10^5 mg.what is the mass percentage of nitrate?

Answer 1

Mass percentage of nitrate = 67.74%

Step-by-step explanation

Number of moles of cobalt nitrate = 1.56 moles

Mass of the cobalt nitrate = 2.85 x 10⁵ mg

First, convert 2.85 x 10⁵ mg cobalt nitrate to gram

1 mg = 10⁻³ g

Therefore, 2.85 x 10⁵ mg cobalt nitrate = 2.85 x 10⁵ x 10⁻³ = 2.85 x 10² grams

This implies;

1.56 moles of cobalt nitrate → 2.85 x 10² grams cobalt nitrate

1 mole will contains;

`(2.85)/(1.56)*10^2=1.8269*10^2\text{ grams cobalt nitrate}`

Note: Irrespective of oxidation number of cobalt, its molar mass is the same.

Molar mass of cobalt = 58.933193 g/mol

Therefore, the mass of nitrate in the content = (182.69 - 58.933193) = 123.756807 g

`\begin{gathered} Mass\text{ percentage of nitrate }=\frac{\text{mass of nitrate}}{\text{mass of cobalt nitrate}}*100 \\ Mass\text{ percentage of nitrate }=(123.756807)/(182.69)*100 \\ Mass\text{ percentage of nitrate }=67.74\% \end{gathered}`