Question

Four beakers containing potassium nitrate dissolved in water are allowed to evaporate to dryness. Beakers 1 through 4 contain 2.3, 1.91, 5.985, and 0.52 g of dry potassium nitrate respectively. How many moles of potassium nitrate were recovered after the water evaporated?

Answer 1

Step-by-step explanation:

Molar mass of potassium nitrate will be calculated as follows.

Molar mass
`KNO_(3)` = molar mass of K + molar mass of N + 3 × molar mass of O

= 39.098 g/mol + 14.006 g/mol + 3 × 15.999 g/mol

= 102.102 g/mol

Now, adding the given amount of potassium nitrate present in each beaker as follows.

(2.3 + 1.91 + 5.985 + 0.52) g

= 10.715 g

Therefore, calculate number of moles as follows.

No. of moles =
`\frac{mass}{\text{molar mass}}`

=
`(10.715 g)/(102.102 g/mol)`

= 0.105 mol

Thus, we can conclude that 0.105 moles of potassium nitrate were recovered after the water evaporated.