A smoldering splinter flares up if the volume fraction of oxygen in the air is at least 31%. A portion of potassium

| March 7, 2021 | education

A smoldering splinter flares up if the volume fraction of oxygen in the air is at least 31%. A portion of potassium permanganate was decomposed in a closed vessel filled with air with a volume of 200 dm3 (the volume fraction of oxygen in the air is 21%). Calculate the minimum mass of KMnO4 if a smoldering splinter breaks out in a vessel.

Let’s write down given:

V (air) = 200 dm3 = 200 l

At ϕ (О2) = 31%, the

ϕ (O2 in air) = 21%

m (KMnO4) -?

Decision:

1) Calculate the volume of oxygen in a 200 liter vessel if it is filled with air:

200L of air is 100%

Chl oxygen is 21%

X = 200 * 21/100

X = 42 l (O2)

2) Calculate the volume of oxygen in a 200 L vessel if it is filled with air containing 31% oxygen:

200L of air is 100%

Chl oxygen is 31%

X = 200 * 31/100

X = 62 l (O2)

3) Let’s calculate how much oxygen needs to be additionally obtained:

62 l – 42 l = 20 l

4) Write down the reaction equation and calculate the mass of potassium permanganate:

2 KMnO4 = K2MnO4 + MnO2 + О2

M (KMnO4) = 39 + 55 + 16 * 4 = 158 g / mol

V m = 22.4 l / mol

From 2 * 158 g (KMnO4) 22.4 l (O2) is formed

From x g (KMnO4) 20 l (O2) is formed

X = 2 * 158 g * 20 l / 22.4 l

X = 282 g (KMnO4)

Answer: 282 g (KMnO4)



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