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We can identify a pure substance from its melting point or boiling point. Put water in a test-tube and hold a thermometer with the bulb just under the water. Add boiling chips to prevent bumping. Bring the water to the boil with a very small flame and read the thermometer. Note any change in the reading if the thermometer touches the bottom of the test-tube.
sharon kalunda answered the question on April 11, 2019 at 08:57
- State three examples of allotropes of carbon(Solved)
State three examples of allotropes of carbon.
Date posted: April 9, 2019. Answers (1)
- Define the following terms as used in chemistry: atom,molecule, element and compound(Solved)
Define the following terms as used in chemistry: atom,molecule, element and compound
Date posted: April 9, 2019. Answers (1)
- Describe how the mixture of sugar, iodine and lead (II) carbonate can be separated(Solved)
Describe how the mixture of sugar, iodine and lead (II) carbonate can be separated.
Date posted: April 9, 2019. Answers (1)
- Explain why elements in group eight are inert. Give one use of argon that depends on this characteristics . (Solved)
Explain why elements in group eight are inert. Give one use of argon that depends on this characteristics.
Date posted: April 3, 2019. Answers (1)
- Differentiate between oxidation and reduction. (Solved)
Differentiate between oxidation and reduction.
Date posted: April 3, 2019. Answers (1)
- Study the scheme below and answer the questions that follow.(Solved)
(a) Identify solid E.
(b) Write an ionic equation for the reaction in step II that produces solid F.
Date posted: April 1, 2019. Answers (1)
- Use the information in the table below to answer the questions that follow. (The letters do not
represent the actual symbols of the elements.(Solved)
Use the information in the table below to answer the questions that follow. (The letters do not
represent the actual symbols of the elements.
(a) Which two letters represent the same element ? Give a reason.
(b) Give the number of neutrons in an atom of element D.
Date posted: April 1, 2019. Answers (1)
- The diagram below shows an investigation on a property of ammonia gas.(Solved)
The diagram below shows an investigation on a property of ammonia gas.
(a) The platinum wire is observed to glow. Explain the cause of that observation.
(b) State the observations made when the rubber bang is removed.
Date posted: April 1, 2019. Answers (1)
- The molar masses of gases W and X are 16.0 and 44.0 respectively. If the rate of diffusion of W through porous material is 12cm3s-1....(Solved)
The molar masses of gases W and X are 16.0 and 44.0 respectively. If the rate of diffusion of W through porous material is 12cm3s-1. Calculate the rate of diffusion of X through the same material.
Date posted: April 1, 2019. Answers (1)
- Your lab technician noted that the reagent bottles of sodium carbonates, sodium chloride and sugar
have lost their labels. Your Chemistry teacher requested you to prepare...(Solved)
Your lab technician noted that the reagent bottles of sodium carbonates, sodium chloride and sugar
have lost their labels. Your Chemistry teacher requested you to prepare and test aqueous solutions of
each sample as shown below.
Complete the table by filling the correct label for each bottle.
Date posted: April 1, 2019. Answers (1)
- Imagine that you used the set up shown in the diagram below in order to study the reactions of some metals with steam. The experiment...(Solved)
Imagine that you used the set up shown in the diagram below in order to study the reactions of some metals with steam. The experiment was carried out for ten minutes.
(a) What observation would be made if gas F is ignited ?
(b) When the experiment was repeated using iron powder instead of magnesium ribbon
very little gas F was obtained.
(i) Give a reason for this observation.
(ii) What change in the conditions of the experiment should the student have made in
order to increase the volume of the gas F produced?
Date posted: April 1, 2019. Answers (1)
- The lattice energy of sodium bromide and hydration energies of sodium and bromide ions are:- 733, 406 and 335kJ/mol respectively.(Solved)
The lattice energy of sodium bromide and hydration energies of sodium and bromide ions are:- 733, 406 and 335kJ/mol respectively.
(i) Complete the energy cycle diagram below by inserting the values of changeH1, changeH2 and changeH3.
(ii) Determine the molar heat of solution of solid sodium bromide.
Date posted: April 1, 2019. Answers (1)
- What is meant by molar heat of solution ?(Solved)
What is meant by molar heat of solution ?
Date posted: April 1, 2019. Answers (1)
- Using dots (.) and crosses (x), show bonding in:-Sodium oxide (Na = 11; O = 8 )(Solved)
Using dots (.) and crosses (x), show bonding in:-Sodium oxide (Na = 11; O = 8 )
Date posted: April 1, 2019. Answers (1)
- Using dots (.) and crosses (x), show bonding in:The compound formed when nitrogen reacts with fluorine. (F = 9, N = 7)(Solved)
Using dots (.) and crosses (x), show bonding in:The compound formed when nitrogen reacts with fluorine. (F = 9, N = 7)
Date posted: April 1, 2019. Answers (1)
- 20.0cm3 of a solution containing 4gm per litre of sodium hydroxide was neutralized by
8.0cm3 of dilute sulphuric acid. Calculate the concentration of sulphuric acid in...(Solved)
20.0cm3 of a solution containing 4gm per litre of sodium hydroxide was neutralized by
8.0cm3 of dilute sulphuric acid. Calculate the concentration of sulphuric acid in moles per litre.( Na = 23.0; O = 16.0; H = 1.0 )
Date posted: April 1, 2019. Answers (1)
- The diagram below represents a paper chromatogram for three brands of juices suspected to contain banned food colourings by the Kenya Bureau of Standards.(Solved)
The diagram below represents a paper chromatogram for three brands of juices suspected to contain banned food colourings by the Kenya Bureau of Standards.
The results showed the presence of banned food colourings in L and M only. On the same diagram
(a) Circle the spots which show the banned food colourings.
(b) Show the solvent front.
(c ) Name one possible solvent that can be used in this experiment / research.
Date posted: April 1, 2019. Answers (1)
- Use the electrochemical series below to answer the questions that follow.(Solved)
Use the electrochemical series below to answer the questions that follow.
Calculate the E.M.F for the electrochemical cell represented below.
Date posted: April 1, 2019. Answers (1)
- A form four student prepared potassium sulphite solution and divided it into two portions.The first portion gave a white precipitate when reacted with barium nitrate....(Solved)
A form four student prepared potassium sulphite solution and divided it into two portions.The first portion gave a white precipitate when reacted with barium nitrate. On addition of dilute hydrochloric acid, the white precipitate disappeared.
(a) Write the formula of the compound which formed as the white precipitate.
(b) Write the equation for the reaction between dilute hydrochloric acid and the
compound whose formula is written in (a) above.
Date posted: April 1, 2019. Answers (1)
- A compound whose structure is shown below is found in a detergent, used in our day to day activities.(Solved)
A compound whose structure is shown below is found in a detergent, used in our day to day activities.
With reference to the structure, explain how the detergent removes grease during washing.
Date posted: April 1, 2019. Answers (1)