A hydrate of copper(II) sulfate, when heated, goes through the succession of changes suggested by the photograph. In this photograph, 

(a) Is the original fully hydrated copper(II) sulfate; 

(b) Is the product obtained by heating the original hydrate to 140 °C; 

(c) Is the product obtained by further heating to 400 °C; and (d) is the product obtained at 1000 °C.

A 2.574 g sample of CuSO₄ · x H₂O was heated to 140 °C, cooled, and reweighed. The resulting solid was reheated to 400 °C, cooled, and reweighed. Finally, this solid was heated to 1000 °C, cooled, and reweighed for the last time.

Original sample                           2.574 g

After heating to 140 °C               1.833 g

After reheating to 400 °C           1.647 g

After reheating to 1000 °C         0.812 g

(a) Assuming that all the water of hydration is driven off at 400 °C, what is the formula of the original hydrate?

(b) What is the formula of the hydrate obtained when the original hydrate is heated to only 140 °C?

(c) The black residue obtained at 1000 °C is an oxide of copper. What is its percent composition and empirical formula?

Transcribed Image Text:

(a) (b) (c) (d)