Read the following passage and then answer the questions which follow.

Sodium carbonate decahydrate effloresces quite readily. With some substances, such as solid sodium hydroxide, the reverse of efflorescence occurs – they deliquesce. There are some substances, such as concentrated sulfuric acid, which when left open to the atmosphere are diluted – they are hygroscopic.

a. What are the meanings of the terms in italics?

b. What precautions should be taken to ensure that these substances are not involved in the processes described above?

c. Which of the other salts shown in Table 8.6 on p. 127 are likely to effloresce? Give a reason for your answer.

Table 8.6

Salt hydrate Formula
Cobalt(ii) chloride hexahydrate ................................................ CoCl₂.6H₂O
Copper(ii) sulfate pentahydrate ............................................. CuSO₄.5H₂O
Iron(ii) sulfate heptahydrate .................................................... FeSO₄.7H₂O
Magnesium sulfate heptahydrate ......................................... MgSO₄.7H₂O
Sodium carbonate decahydrate ......................................... Na₂CO₃.10H₂O
Sodium hydrogensulfate monohydrate ............................... NaHSO₄.H₂O
Sodium sulfate decahydrate ............................................... Na₂SO₄.10H₂O