# Hi there! If you can help me with these Grade 11 Chemistry questions, that would be fantastic!

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llltkl | College Teacher | (Level 3) Valedictorian

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The molar mass of all the salts are obtained by adding up individual atomic masses of its constituent atoms.

Thus, molar masses of the salts of potassium are:

KCl : (39.01+35.45), i.e. 74.46 g/mol

K2SO4: (2*39.01+32.06+4*16), i.e. 174.08 g/mol

K2O: (2*39.01+16)=94.02 g/mol

1 kg of KCl is 1000/74.46, i.e 13.43003 moles.

From the formula of the salts it is evident that,

1 mole (or atom) of potassium is contained in: 1 mole of KCl,

: 1/2 mole of K2SO4

: 1/2 mole of K2O

1 kg

Therefore, 13.43003 moles (or atoms) of potassium is contained in: 13.43003 moles of KCl,

: 13.43003/2 moles of K2SO4, or 13.43003/2*174.08, i.e. 1.16895 kg of K2SO4

: 13.43003/2 moles of K2O or, 13.43003/2*94.02, i.e. 0.6313457 kg of K2O

a. To supply the same amount of potassium as 1 kg KCl, on a per dollar basis,

1.16895 kg of K2SO4 should cost \$0.55

1.00 kg of K2SO4 should cost \$0.55/1.16895, i.e. \$0.4705 `~~\$0.47` .

b. Mass (in Kg) of K2O that contains the same number of moles of K atoms as 1.00 kg of KCl is 0.6313457 kg `~~0.63 ` kg.

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