1.0.12g of sodium metal is added to a large volume of water. When the reaction is completed, the resulting solution is trated with 0.2M hydrochloride acid. What is the volume of the acid required, to the nearest cm^3, for complete neutralization? (Please show the steps)
2.The following substances were burnt in oxygen and the products were mixed with water. Which of these substances would produce a resulting solution with the highest pH value?
A.calcium
B.iron
C.sulphur
D.carbon
the answer is a but why?pleast explain it to me,thank you:)
關於chem(Acids and Alkalis)既問題
2011-10-25 5:23 am
回答 (1)
2011-10-25 6:19 am
✔ 最佳答案
1. 2Na + 2H2O ---> 2NaOH + H2No. of moles of Na reacted
= 0.12 / 23
= 5.217*10^-3 mol
No. of moles NaOH formed
= 5.217*10^-3 mol
NaOH + HCl --> NaCl + H2O
No. of moles of HCl required
= 5.217*10^-3 mol
Volume of acid required
= 5.217*10^-3 / 0.2 * 1000
= 26 cm^3
2. A is the answer.
For calcium, it can react with oxygen to form calcium oxide. With further treatment with water, calcium hydroxide is formed which is a strong alkali, giving the highest value of pH among the options.
For iron, although it can react with oxygen to form iron(II)(III) oxide. It is not soluble in water, so no aqueous solution can be produced.
For sulphur, it can react with oxygen to produce sulphur dioxide. However, on further treatment with water, it will give sulphurous acid or sulphuirc acid, which should have a low pH, i.e. sulphur dioxide is an acidic gas.
For carbon, it can react with oxygen to produce carbon dioxide. However, on further treatment with water, it will react sparingly to give carbonic acid (weak acid), which should have a slightly lower pH, i.e. carbon dioxide is also an acidic gas.
參考: Knowledge is power.
收錄日期: 2021-04-23 13:32:36
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