Question

Calculate to one decimal place the percentage composition of:

a) KMnO₄

b) If you have 25,490 grams of aluminum oxide, how much aluminum do you have in the compound?

Answer 1

Answer:

a) KMnO4 percentage composition:

KMnO4 molecular weight = 158

K atomic weight = 39

Percentage of potatium:

158 .............. 100

39 ............. ?

= (39 x 100) / 158

= 3900 / 158

= 24.68 %

Percentage on Mn:

KMnO4 molecular weight = 158

Mn atomic weight = 54.93

158 .............. 100

54.93 ............. ?

= (54.93 x 100) / 158

= 34.76 %

Percentage of Oxygen:

KMnO4 molecular weight = 158

O atomic weight = 16

But four oxygen atoms are present

The the weight of Oxygen = 16 x 4 = 64

158 .............. 100

64 ............. ?

= (64 x 100) / 158

= 6400 / 158

= 40.50 %

b) Answer:

Aluminium oxide (Al₂O₃) weight = 25,490 grms.

Al₂O₃ molecular weight = 101.96

Al atomic weight = 27

From the above values,

101.96 g ............. 27g

25,490 g ............. ?

= (25490 x 27) / 101.96

= 688230 / 101.96

= 6,750 grms

Hence the Al weight in the Aluminium oxide is 6,750 grms.