Question

#10,11

10. A student obtains an empirical formula of CH28. a) Why is this not a valid empirical formula? b) Use the student's empirical formula to determine the correct empirical formula. 11. Magnesium sulfate, MgSO4, is available as anhydrous crystals or as a heptahydrate. Assume that you are given a bottle of MgSO4, but you are not sure whether or not it is the hydrate. a) What method would you use in a laboratory to determine whether this is the hydrate? b) If it is the hydrate, what results would you expect to see? c) If it is the anhydrous crystals, what results would you expect to see? ... in mnneed of carb

Answer 1

10.a) The subscript in the empirical formula should be a whole number. In the given formula, 2.67 which is subscript of H is not a whole number.

b) to make 2.67 which is the subscript of H, we will multiply it by 3, so wewill get 8.01 which can be approximated as 8. Hence, the correct empirical formula is C₃H₈

11. a) We can check if a compound is in anhydrous or hydrated form by heating it.

  b) If it is hydrate then on heating MgSO₄, the water of crystallisation will get evaporated and this leads to change in colour.

c) if it is the anhydrous crystals then heating will cause no colour change in it.