Glauberite is a mineral containing sodium sulfate (Mr = 142.0) and calcium
sulfate (Mr = 136.1) only. It is the chief source of sodium sulfate, which is used
in making glass. If a 20.00 g sample of glauberite contains 2.88 g of calcium,
what mass of sodium sulfate can be extracted from 1 tonne (1000 kg) of
glauberite?