Chemistry Past Questions and Answers

When air is passed through alkaline pyrogallol and then over quicklime, the only gases left are?

A Nitrogen and carbondoxide
B The rare gases
C Nitrogen and oxygen
D Nitrogen and the rare gases
E Nitrogen, carbonioxide and the rare gases

Question 277:

9.8g of solid potassium chlorate (KCIO3) were added to 40 cm3 of water and heated to dissolve all the solid. As he solution cooled, crystals of potassium chlorate started forming at 60°C. The solubility of potassium chlorate at 66°C is therefore?

A 24.5 mole per dm3
B 0.2 mole per dm3
C 10.0 mole per dm3
D 20.0 mole per dm3
E 2.0 mole per dm3

Question 278:

100 cm3 of oxygen is made to react with 50 cm 3 of hydrogen, and the whole reaction mixture was then passed through anhydrous calcium chloride. What is the volume of gas left?

A 5 cm3
B 25 cm3
C 50 cm3
D 75 cm3
E 100 cm3

Question 279:

A mixture contains 20cm3 of hydrogen, 35cm3 of oxygen, 15cm3 of carbon monoxide and 10cm3 of nitrogen at S.T.P. Which of the following gives the mole fraction of hydrogen in this mixture?

A 0.02
B 0.16
C 0.20
D 0.25
E 20

Question 280:

0.07g of a hydride of carbon occupies 56.0cm3 at S.T.P. when vaporized and contains 14.29% by mass of hydrocarbon is(C = 12, H = 1)

A CH4
B C2H2
C C2H4
D C2H6
E C3H8