- The lab setup shown above was used for the gravimetric analysis of the
empirical formula of MgO. In synthesizing MgO from a Mg strip in the
crucible, which of the following is NOT true?
(A) The initial strip of Mg should be cleaned.
(B) The lid of the crucible should fit tightly to exclude oxygen.
(C) The heating of the covered crucible should continue until the Mg is
fully reacted.
(D) The crucible, lid, and the contents should be cooled to room
temperature before measuring their mass.
(E) When the Mg appears to be fully reacted, the crucible lid should be
partially removed and heating continued.
Questions 48–50 refer to the following experimental scenario and data:
A sample of the hydrated form of barium chloride is placed into an evaporating
dish and heated strongly for 20 minutes on a hot plate. After cooling in a
desiccator, the mass of the dish and contents is determined. The whole system is
then heated strongly again for 5 minutes and cooled. Then the mass is measured
again. The heating, cooling, and measuring of the mass is repeated a third time.
Recorded Data:Mass of evaporating dish
= 14.30 gMass of dish and hydrated BaCl 2
= 26.50 gMass of dish and anhydrous BaCl 2 (after 1st heating)
= 24.77 gMass of dish and anhydrous BaCl 2 (after 2nd heating)
= 24.70 g