Question

calculating mass quick check
use the chemical equation to answer the question.
4k(s) + o₂(g) → 2k₂o(s)
the molar mass of potassium (k) is 39 g/mol. the molar mass of oxygen (o) is 16 g/mol. how many grams of potassium are needed in the reaction to produce 23.5 grams of potassium oxide (k₂o)?
(1 point)
○ 9.75 g
○ 0.50 g
○ 19.5 g
○ 23.5 g

Explanation:

Step1: Calculate molar mass of \(K_2O\)

Molar mass of \(K_2O=(2\times39)+16 = 94\space g/mol\)

Step2: Calculate moles of \(K_2O\)

Moles of \(K_2O=\frac{23.5\space g}{94\space g/mol}= 0.25\space mol\)

Step3: Use mole ratio from chemical equation

From \(4K(s)+O_2(g)\to2K_2O(s)\), mole ratio of \(K\) to \(K_2O\) is \(4:2 = 2:1\). So moles of \(K = 2\times0.25\space mol=0.5\space mol\)

Step4: Calculate mass of \(K\)

Mass of \(K=0.5\space mol\times39\space g/mol = 19.5\space g\)

Answer:

19.5 g