Use the chemical equation to answer the question.

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)
Responses

23.5 g
23.5 g

19.5 g
19.5 g

9.75 g
9.75 g

0.50 g

Answer 1

To find out how many grams of potassium (K) are needed to produce 23.5 grams of potassium oxide (K2O), we will follow these steps:

1. Calculate the molar mass of K2O: \[ \text{Molar mass of K2O} = (2 \times \text{molar mass of K}) + (1 \times \text{molar mass of O}) = (2 \times 39 , \text{g/mol}) + (1 \times 16 , \text{g/mol}) = 78 , \text{g/mol} + 16 , \text{g/mol} = 94 , \text{g/mol} \]

2. Convert grams of K2O to moles: \[ \text{Moles of K2O} = \frac{\text{mass}}{\text{molar mass}} = \frac{23.5 , \text{g}}{94 , \text{g/mol}} \approx 0.250 , \text{mol} \]

3. Use the balanced equation to find moles of K needed: From the balanced equation, the molar ratio of K to K2O is 4:2, or 2:1. Thus, for every 1 mole of K2O produced, 2 moles of K are needed. \[ \text{Moles of K needed} = 2 \times \text{moles of K2O} = 2 \times 0.250 , \text{mol} = 0.500 , \text{mol} \]

4. Convert moles of K to grams: \[ \text{Mass of K} = \text{moles} \times \text{molar mass} = 0.500 , \text{mol} \times 39 , \text{g/mol} = 19.5 , \text{g} \]

So, the amount of potassium required to produce 23.5 grams of potassium oxide is 19.5 grams.

Therefore, the correct response is: 19.5 g.