How much does the chlorine (Cl) weigh in 720 grams of potassium chlorate.

Question

How much does the chlorine (Cl) weigh in 720 grams of potassium chlorate (KCIO₃)? (K, 39; Cl, 35; O, 16)

(A) 206 (34)/(61) g

(B) 280 g

(C) 2509 (5)/(7) g

(D) 144 g

(E) None of these

Answer 1

The answer is A 206 g. We can tell this by finding the percentage of Potassium Chlorate that is chlorine by weight. For 1 mole of Potassium Chlorate we can find the weight of each element by multiplying the atomic weight by the subscript. Potassium 39g (39g x 1 potassium/mole), Chlorine 35g ( 35 g x 1 Chlorine/mole), Oxygen 48g (16g x 3 oxygen/mole), we can then sum these 3 numbers and find that their are 122 grams in every mole of Potassium Chlorate. By dividing 35g of chlorine by 122 grams total, we can find that .2869 or 28.69% of the weight of the Potassium Chlorate is due to Chlorine. We can then multiply the total known weight by the percentage to find the total weight that is Chlorine: 720g*0.2869=206g.