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39. 200 cm3 of a gas Y2 react completely with 300 cm3 of oxygen to form 200 cm3 of a gaseous oxide. If all measurement are made at room temperature and pressure, the formula of the gaseous oxide is:
A YO2
B. Y2O
C. Y2O3
D. Y3O2
36. Which of the following solution has the lowest pH value?
A. 25 cm3 of 1M HCL
B. 50 cm3 of 1M CH3COOH
C. 50 cm3 1M H2CO3
D. 25 cm3 of 1M H2SO4
chem mc questions..........
2007-04-19 7:15 pm
回答 (2)
2007-04-19 7:33 pm
✔ 最佳答案
39.No. of moles of Y2=(200/1000)/24=1/120
No. of moles of O2=(300/1000)/24=1/80
No. of moles of Y2:No. of moles of O2=No of atoms of Y:No of atoms of O=2:3
Ans is C
36.
D
Volume does not affect the pH value of a solution
For A:HCl is a strong monobasic acid.1M of HCl gives 1M of H+ ions
For B&C:They are weak acids which only partly ionize in water.So 1M of acids gives less than 1M of H+ ions
For D:H2SO4 is a strong dibasic acid.1M of H2SO4 gives more than 1M of H+ ions
The equations:H2SO4---->H+ +HSO4-
HSO4(reversible reaction)-----H+ +SO4 2-
2007-04-19 11:34:38 補充：
The equations:H2SO4-------->H+ +HSO4-HSO4(reversible reaction)-----H+ +SO4 2-
2007-04-19 7:29 pm
39. you can assume 2 molecule of Y react with 3 molecule of oxygen to give 2 molecule new gas. you can imagine there are 4 Y and 6 oxygen and react to give 2 Y2O3
36. pH is independent of the volume. H2SO4 give 2 H+ ion per molecule and it has the lowest pH value
36. pH is independent of the volume. H2SO4 give 2 H+ ion per molecule and it has the lowest pH value
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