A 5.00 gram sample of ZnSO4*7H2O was heated until dry. What is the mass of ZnSO4 remaining?

Question

Please help me solve this problem .

Answer 1

First, assess the molar mass of ZnSO₄*7H₂O:

 

ZnSO₄: Zn+S+4*O=65.38+32.06+4*16.00=161.44 grams/mol

7H₂O: 14H+7O = 14*1.008+7*16.00=126.105 grams

Total mass of 1 mole ZnSO4*7H₂O = 161.44+126.105= 287.55

 

Next: assess the numbers of mole ZnSO4*7H₂O: divide 5.00 gram by the molar mass:

5.00 gram/287.55 gram/mole = 0.0174 mole ZnSO4*7H₂O

 

Evaporation the water results in 0.0174 mol ZnSO₄. Use reaction equation for mole ratio

Finally: convert mole ZnSO₄ to grams: multiplying with the molar mass of ZnSO₄ (161.44, see above)

0.0174 mole * 161.44 gram/mole = 2.81 gram

 

Hope this helps, good luck