Subject: Chemistry 12
Number of Questions: 6 (or max. number available)
1.) What is observed when H2SO4 is added to a saturated solution of CaSO4?
the [Ca2+] increases
the pH increases
additional CaSO4 precipitates
bubbles of H2 are given off
explain why
When H2SO4 (sulfuric acid) is added to a saturated solution of CaSO4 (calcium sulfate), additional CaSO4 precipitates. This is because H2SO4 is a strong acid that can neutralize the weak base CaSO4. The reaction between them goes as follows:
H2SO4 + CaSO4 -> Ca(HSO4)2
In this reaction, H2SO4 donates protons (H+) to CaSO4, forming calcium bisulfate (Ca(HSO4)2) as a product. The formation of calcium bisulfate is an example of a double displacement reaction.
Since the newly formed product, calcium bisulfate, is not very soluble in water and is less soluble than CaSO4, it will precipitate out of the solution. As a result, the concentration of Ca2+ ions in the solution decreases as the Ca2+ ions are being used to form the insoluble calcium bisulfate.