a) 2H2O2(l) $\rightarrow$ 2H2O(l) + O2(g)
b) Oxygen is insoluble (or slightly soluble) in water.
c) To ensure that the air that occupied the apparatus initially is expelled.
johnmulu answered the question on April 6, 2017 at 08:57
- A student added very dilute sulphuric (VI) acid to four substances and recorded the observations shown in the table below.(Solved)
A student added very dilute sulphuric (VI) acid to four substances and recorded the observations shown in the table below.
For which tests are the observations wrong? Explain.
Date posted: April 6, 2017. Answers (1)
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Study the diagram below and answer the questions that follow.
Write an equation for each of the two reactions that takes place in the experiment represented by the diagram
Date posted: April 6, 2017. Answers (1)
- a) Explain what happens to the molecules of water in the region BC in terms of Kinetic theory.
b) In what state is the water in the region DE?
(Solved)
The graph below is a cooling curve for water. Study it and answer the questions that follow.
a) Explain what happens to the molecules of water in the region BC in terms of Kinetic theory.
b) In what state is the water in the region DE?
Date posted: April 6, 2017. Answers (1)
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The set up below was used to separate a mixture of methanol and propanol. Study it and answer the questions that follow.
a) State the function of X.
b) Which liquid will collect first in the beaker? Given a reason.
Date posted: April 6, 2017. Answers (1)
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The chromatogram below was obtained from a contaminated food sample P. Contaminants Q,R,S and T are suspected to be in P. Use it to answer the following questions.
a) Identify the contaminant in mixture P?
b) Which is the most soluble contaminant in P?
Date posted: April 6, 2017. Answers (1)
- Classify the following processes as either chemical or physical.(Solved)
Classify the following processes as either chemical or physical.
Date posted: April 6, 2017. Answers (1)
- The graph below is a cooling curve of a substance from gaseous state to solid state.(Solved)
The graph below is a cooling curve of a substance from gaseous state to solid state.
Give the name of the: a) Process taking place between to and t1
b) energy change that occurs between between t3 and t4
Date posted: April 6, 2017. Answers (1)
- Sample of urine from three participants F, G and H at an international sports(Solved)
Sample of urine from three participants F, G and H at an international sports meeting were spotted onto a chromatography paper alongside two from illegal drugs A1 and A2. A chromatogram was run using methanol. The figure below shows the chromatogram.
a) Identify the athlete who had used an illegal drug.
b) Which drug is more soluble in methanol?
Date posted: April 6, 2017. Answers (1)
- The graph below shows a curve obtained when water at 20o was heated for 15 minutes.(Solved)
The graph below shows a curve obtained when water at 20o was heated for 15 minutes.
a) What happens to the water molecules between points W and X?
b) In which part of the curve does a change of state occur?
c) Explain why the temperature does not rise between points X and Y.
Date posted: April 6, 2017. Answers (1)
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a) Study the properties of substances V2 and V4 in the table below and answer the questions that follows.
a) Which of the substances are liquid at 24oC?
b) Describe how a mixture containing V2 and V4 can be separated.
Date posted: April 6, 2017. Answers (1)
- A piece of chromatography paper was spotted with coloured inks obtained from pens labeled 1 to 6. The diagram below show the spots after the chromatogram was developed.(Solved)
A piece of chromatography paper was spotted with coloured inks obtained from pens labeled 1 to 6. The diagram below show the spots after the chromatogram was developed.
a) Which two pens contained the same pigment?
b) Which pens contained only one pigment?
c) According to the chromatogram, which pigment are present in the ink of pen number 6?
Date posted: April 5, 2017. Answers (1)
- The set-Up below represents the apparatus that may be used to separate a mixture of two miscible liquids C and D whose boiling points are 80oC and 110oC.(Solved)
The set-Up below represents the apparatus that may be used to separate a mixture of two miscible liquids C and D whose boiling points are 80oC and 110oC.
a) Name B
b) What is the purpose of the thermometer?
c) Which liquid was collected in the test tube?
Date posted: April 5, 2017. Answers (1)
- The diagram below shows the relationships between the physical state of matter. Study it and answer the questions that follow.(Solved)
The diagram below shows the relationships between the physical state of matter. Study it and answer the questions that follow.
a) Identify the processes R, V, W and U.
b) Name one substance which can undergo the process represented by S and T
c) Explain whether process W is exothermic or endothermic
Date posted: April 5, 2017. Answers (1)
- In an experiment to separate a mixture of two organic liquids, Liquid M (b.p 56oC) and liquid N (b.p.118oC), a student set up the apparatus shown below(Solved)
In an experiment to separate a mixture of two organic liquids, Liquid M (b.p 56oC) and liquid N (b.p.118oC), a student set up the apparatus shown below
a) Identify two mistakes in the set-up.
b) What method would the student use to test the purity of the distillates obtained?
Date posted: April 5, 2017. Answers (1)
- The curve below represents the variation of temperature with time pure and impure samples of a solid were heated separately.(Solved)
The curve below represents the variation of temperature with time pure and impure samples of a solid were heated separately.
Which curve shows the variation in temperature for pure solid? Explain.
Date posted: April 5, 2017. Answers (1)
- a) Distinguish between a neutron and a proton.
b) What is meant by a radioactive substance
c) State two dangers associated with radioactive substance in the environment(Solved)
a) Distinguish between a neutron and a proton.
b) What is meant by a radioactive substance
c) State two dangers associated with radioactive substance in the environment
Date posted: February 22, 2017. Answers (1)
- Distinguish between nuclear fission and nuclear fusion and describe how solid wastes containing radioactive substance should be disposed off. (Solved)
a) Distinguish between nuclear fission and nuclear fusion.
b) Describe how solid wastes containing radioactive substance should be disposed off.
Date posted: February 22, 2017. Answers (1)
- State two factors which determine the stability of an isotope.(Solved)
State two factors which determine the stability of an isotope.
Date posted: February 22, 2017. Answers (1)
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State two differences between chemical and nuclear reactions.
Date posted: February 22, 2017. Answers (1)
- M grammes of a radioactive isotope decayed to 5 grammes in 100 days
The half-life of the isotope is 25 days(Solved)
M grammes of a radioactive isotope decayed to 5 grammes in 100 days
The half-life of the isotope is 25 days
a) What is meant by half-life?
b) Calculate the initial mass M of the radioactive isotope.
Date posted: February 22, 2017. Answers (1)