a) To generate steam which pushes out the air.
b) The air would oxidize zinc oxide hence no gas would be collected
c) It is less dense than air.
johnmulu answered the question on April 7, 2017 at 08:27
- The diagram below represents a set-up that was used to react lithium with water. Study it and answer the questions that follow:
(Solved)
The diagram below represents a set-up that was used to react lithium with water. Study it and answer the questions that follow:
a) Write an equation for the reaction that takes place, given that the atomic number of lithium is 3.
b) Why would it not be advisable to use potassium in place of lithium in the above set-up?
Date posted: April 7, 2017. Answers (1)
- In an experiment, rod of metals P, Q and R were cleaned with sand paper and placed in a beaker containing water.(Solved)
In an experiment, rod of metals P, Q and R were cleaned with sand paper and placed in a beaker containing water. Another set of rod was also cleaned and placed in a beaker containing dilute acid. After placing the rods in the two liquids bubbles of gas were seen around some of the rods as shown in the diagrams below.
a) Why is it necessary to clean the rods with sand paper before dipping them into the liquids.
b) Arrange the three metals in order of their reactivity starting with the most reactive
Date posted: April 6, 2017. Answers (1)
- A measuring cylinder fitted with moist steel wool was inverted in a trough of water as shown in the diagram below.(Solved)
A measuring cylinder fitted with moist steel wool was inverted in a trough of water as shown in the diagram below.
a) State and explain the observations made on the:
i) Moist steel wool after four days
ii) Water level in the measuring cylinder after four days.
b) What would be the effect of using steel wool moistened with salty water?
Date posted: April 6, 2017. Answers (1)
- The set up below can be used to prepare oxygen gas. Study it and answer the questions that follow.(Solved)
The set up below can be used to prepare oxygen gas. Study it and answer the questions that follow.
a) Identify X
b) What property of oxygen makes it possible for it to be collected as shown in the above set up?
c) State two uses of oxygen.
d) Write a balanced chemicals equation for the reaction that takes place in the reaction flask.
Date posted: April 6, 2017. Answers (1)
- The following set up of three test-tubes was used to investigate rusting of iron. Study it and answer the questions that follow.(Solved)
The following set up of three test-tubes was used to investigate rusting of iron. Study it and answer the questions that follow.
a) Give a reason why rusting did not occur in test-tube C.
b) A luminium is used to protect iron sheets from rusting. Explain two ways in which aluminium protects iron from rusting.
Date posted: April 6, 2017. Answers (1)
- In an experiment, dry hydrogen gas was passed over heated Lead (II) Oxide as shown in the diagram below.
(Solved)
In an experiment, dry hydrogen gas was passed over heated Lead (II) Oxide as shown in the diagram below.
State and explain the observations made in the combustion tube
Date posted: April 6, 2017. Answers (1)
- The diagram below represents a set-up that was used to show that part of air is used during burning.(Solved)
The diagram below represents a set-up that was used to show that part of air is used during burning.
a) Given that phosphorus used was used in excess, draw a diagram of the set-up at the end of the experiment (when there was no further observable change).
b) Suggest one modification that should be made on the apparatus if the percentage of the air used is to be determined.
Date posted: April 6, 2017. Answers (1)
- Air was passed through several reagents as shown in the flow chart below(Solved)
Air was passed through several reagents as shown in the flow chart below
a) Write an equation for the reaction which takes place in the chamber with magnesium powder.
b) Name one gas which escapes from the chamber containing magnesium powder. Give reason for your answer.
Date posted: April 6, 2017. Answers (1)
- The diagram below is a set-up for the laboratory preparation of oxygen gas(Solved)
The diagram below is a set-up for the laboratory preparation of oxygen gas
a) Name solid R.
b) Write an equation for the reaction that takes place in the flask.
c) Give one commercial use of oxygen.
Date posted: April 6, 2017. Answers (1)
- The oxides of elements A and B have the properties shown in the table below. (the letters do not represent the actual symbols of elements)(Solved)
The oxides of elements A and B have the properties shown in the table below. (the letters do not represent the actual symbols of elements)
Give one example of elements A and B
Date posted: April 6, 2017. Answers (1)
- The diagram below shows an iron bar which supports a bridge. The iron bar is connected to a piece of magnesium metal.(Solved)
The diagram below shows an iron bar which supports a bridge. The iron bar is connected to a piece of magnesium metal.
Explain why it is necessary to connect the piece of magnesium metal to the iron bar.
Date posted: April 6, 2017. Answers (1)
- In an experiment a certain volume of air was passed repeatedly from syringe to syringe over heated excess zinc powder as shown in the diagram below.(Solved)
In an experiment a certain volume of air was passed repeatedly from syringe to syringe over heated excess zinc powder as shown in the diagram below.
The experiment was repeated using excess magnesium powder. In which of two experiments was the change in the volume of air greatest? Give reasons.
Date posted: April 6, 2017. Answers (1)
- The set-Up below was used to study some properties of air.(Solved)
The set-Up below was used to study some properties of air.
State and explain two observations that would be made at the end of the experiment.
Date posted: April 6, 2017. Answers (1)
- The diagram below represents a set-up that can be used to prepare and collect oxygen(Solved)
The diagram below represents a set-up that can be used to prepare and collect oxygen
a) Write an equation for the reaction that takes place.
b) What property of oxygen makes it possible for its collection as indicated by the diagram?
c) Explain why it is important not to collect any gas for the first few seconds of the experiment.
Date posted: April 6, 2017. Answers (1)
- 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)
- Study the diagram below and answer the questions that follow.(Solved)
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)
- The set up below was used to separate a mixture of methanol and propanol. Study it and answer the questions that follow.(Solved)
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)
- 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.(Solved)
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)