Question

The double replacement reaction between calcium nitrate (Ca(NO​3​)​2)​ and potassium oxide (K​2O​ ) is shown below:

Ca(NO​3)​ ​2​ + K2​ O​ → CaO + KNO​3
How many grams of potassium oxide would be needed to produce 5.00 g of potassium nitrate (​KNO​3)​ ?

Answer 1

Mass = 2.355 g

Explanation:

Given data:

Mass of K₂O needed = ?

Mass of KNO₃ produced = 5.00 g

Solution:

Chemical equation:

K₂O + Ca(NO₃)₂ → CaO + 2KNO₃

Number of moles of KNO₃:

Number of moles = mass/molar mass

Number of moles = 5.00 g/ 101.1 g/mol

Number of moles = 0.05 mol

now we will compare the moles of KNO₃ and K₂O.

KNO₃ : K₂O

2 : 1

0.05 : 1/2×0.05 = 0.025 mol

Mass of potassium oxide needed in gram:

Mass = number of moles × molar mass

Mass = 0.025 mol × 94.2 g/mol

Mass = 2.355 g