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Form 1 Chemistry Topical Questions and Answers on Air and Combustion
Name another gas which is used together with oxygen in welding.
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1.
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 few seconds of the experiment.
2.
Explain how you would separate a mixture of nitrogen and oxygen gases given that their boiling points are #-196^0c# and #-183^0c# respectively.
3.
When magnesium metal is burnt in air, it reacts with both oxygen and nitrogen gases giving a white ash. Write two equations for the reactions that take place.
4.
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.
5.
In an experiment a certain volume of air was passed repeatedly from syringe to 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.
6.
Name another gas which is used together with oxygen in welding.
7.
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 iron metal
8.
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
9.
The diagram below is a setup 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.
10.
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 a reason for your answer.
11.
When wood is burnt, a grey powder called ash remains. The ash is stirred with water and filtered, a colourless solution is obtained. a)what is the main component of the colourless solution? (b)Explain your answer in (a)above.
12.
In an experiment. A piece of magnesium ribbon was cleaned with steel wool. 2.4g of the clean magnesium ribbon was placed in a crucible and completely burnt in oxygen. After cooling, the product weighed 4.0g. (a) Explain why it was necessary to clean the magnesium ribbon? (b)what observation was made in the crucible after burning?
13.
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 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.
14.
A water trough, aqueous sodium hydroxide, burning candle, watch glass and a graduated gas jar were used in an experiment set up to determine the percentage of active part of air. Draw a labelled diagram of the setup at the end of the experiment.
15.
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.
16.
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 the test-tube C
17.
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.
18.
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 observation made on the: i) moist steel wool after four days.
19.
Using the elements chlorine, calcium and phosphorous: (a) Select elements that will form an Oxide whose aqueous solution has a pH less than 7. (b) Write an equation for the reaction between calcium oxide and dilute hydrochloric acid. (c) Give one use of calcium Oxide.
20.
The flow chart in figure 3 shows the process of obtaining a sample of nitrogen gas. Study it answer the questions that follow. (a) Identify X (b) Write an equation for the reaction with heated copper turnings. (c) Name an impurity in the sample of nitrogen gas.
21.
Using iron fillings, describe an experiment that can be conducted to show that oxygen is present in air.
22.
During laboratory preparation of oxygen, manganese(IV)Oxide is added to reagent H. (a) Name reagent H (b) State the role of Manganese(IV)Oxide in the experiment. (c) Write an equation for the reaction that takes place.
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