gsh asked in 教育及參考書標準及測試 · 1 decade ago

F.5 chem problems

I came across with some chem problem while doing mock papers, please do me a favour.

1. 3g of magnesium ribbon is added into 100 cm3 of 2M magnesium nitrate solution. Calculate the molarity of magnesium nitrate after 50cm3 of 1.5M HNO3 is added into the solution.

Answer: 1.58M

2.Mixture of MCO3 and NHCO3 is titrated against H2A. 110cm3 of 0.05M H2A is used for complete reaction. 168cm3 of CO2 gas is collected. What is the mole ratio of MCO3 to NHCO3?

ans: 4:3

3. 5g of zinc and 5g of copper powder are burnt in air at room temperature and pressure separately.

ans: volume of oxygen used is smaller with zinc and the rate of reaction is faster with zinc

4. is carbon monoxide an acidic or alkaline gas?

5. When 3.2M of 25cm3 AgNO3 is mixed with 1.3M of 10cm3 MgCl2, AgCl is precipitated out. Calculate the number of moles of excess Ag- ions in the resulting solution.

ans: 0.054mol

6. A student added an unknown solution to a soapy detergent. The cleaning ability of this soapy detergent is greatly reduced. The unknown solution is:

ans: a mixture of magnesium intrate and calcium nitrate

*For the questions with answer, I simply don't understand how I can get the answer and the principal behind. Please give me a hand if you could. 20 marks are given. Thanks!

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