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- The curve shown below was obtained when solid naphthalene was heated to boiling.(Solved)
The curve shown below was obtained when solid naphthalene was heated to boiling.
(a) Explain in molecular terms the changes occurring in portions.
(i) AB.
(ii) DE.
(b) What is the significance of portion BC?
Date posted: March 29, 2019. Answers (1)
- 3.22g of hydrated sodium sulphate, Na2SO4.XH2O were heated to a constant mass of 1.42g. Determine the value of X in the formula. (Na = 23.0,...(Solved)
3.22g of hydrated sodium sulphate, Na2SO4.XH2O were heated to a constant mass of 1.42g. Determine the value of X in the formula. (Na = 23.0, S = 32.0, O = 16.0, H = 1).
Date posted: March 29, 2019. Answers (1)
- The figure below shows a set-up used in electrolysis of lead iodide.(Solved)
The figure below shows a set-up used in electrolysis of lead iodide.
(a) Why is heating necessary?
(b) Write the equation of the reaction that occurs at the cathode.
(c) At which electrode does reduction occurs.
Date posted: March 29, 2019. Answers (1)
- Solid J reacts with cold water but solid K does not. L reduces the oxide of M but does not reduce the oxide of K....(Solved)
Solid J reacts with cold water but solid K does not. L reduces the oxide of M but does not reduce the oxide of K. Arrange the elements in order of reactivity starting with the most reactive.
Date posted: March 29, 2019. Answers (1)
- In terms of structure and bonding explain why the component Cl2O has a very low melting and boiling point.(Solved)
In terms of structure and bonding explain why the component Cl2O has a very low melting and boiling point.
Date posted: March 29, 2019. Answers (1)
- Draw a dot (.)/cross (X) diagram to show bonding in Cl2O. (Cl = 17, O = 8).(Solved)
Draw a dot (.)/cross (X) diagram to show bonding in Cl2O. (Cl = 17, O = 8).
Date posted: March 29, 2019. Answers (1)
- The following chromatogram was obtained in an experiment to investigate the components present in certain dyes.(Solved)
The following chromatogram was obtained in an experiment to investigate the components present in certain dyes.
(a) Which two dyes when mixed would produce A?
(b) Which dye is pure?
(c) Indicate on the diagram the solvent front.
Date posted: March 29, 2019. Answers (1)
- 1.26g of lead powder were dissolved in excess nitric (VI) acid to form lead nitrate solution. All the lead nitrate solution was reacted with sodium...(Solved)
1.26g of lead powder were dissolved in excess nitric (VI) acid to form lead nitrate solution. All the lead nitrate solution was reacted with sodium sulphate solution.
(a) Write an ionic equation for the reaction between lead nitrate and sodium sulphate solutions.
(b) Determine the mass of lead salt formed in (a) above (Pb = 207, S = 32, O = 16).
Date posted: March 29, 2019. Answers (1)
- A dry cell is constructed using the following substances. Zinc metal, graphite rod, ammonium chloride paste and manganese (IV) oxide mixed with carbon powder.
(a) State...(Solved)
A dry cell is constructed using the following substances. Zinc metal, graphite rod, ammonium chloride paste and manganese (IV) oxide mixed with carbon powder.
(a) State the roles of:
(i) Ammonium chloride paste.
(ii) Manganese (IV) oxide mixed with carbon powder.
(b) Given that:
Calculate the e m f of the cell given zinc forms the negative electrode.
Date posted: March 29, 2019. Answers (1)
- Dry hydrogen chloride gas was passed over heated iron wool as shown below.(Solved)
Dry hydrogen chloride gas was passed over heated iron wool as shown below.
(a) State the observation made in the combustion tube at the end of the experiment.
(b) Write the equation for the reaction taking place:-
(i) In the combustion tube.
(ii) Leading to production of the blue flame.
Date posted: March 29, 2019. Answers (1)
- A mass of 40g of a saturated solution of potassium chlorate at 250C yields 14g of potassium chlorate when evaporated to dryness. Calculate the solubility...(Solved)
A mass of 40g of a saturated solution of potassium chlorate at 250C yields 14g of potassium chlorate when evaporated to dryness. Calculate the solubility of potassium chloride at 250C.
Date posted: March 29, 2019. Answers (1)
- The diagram below is a set-up of apparatus used to react ammonia gas with iron (IV) chloride solution.(Solved)
The diagram below is a set-up of apparatus used to react ammonia gas with iron (IV) chloride solution.
(a) State the observation made in the beaker after a few minutes.
(b) Explain why the funnel is used to deliver the ammonia into the solution.
Date posted: March 29, 2019. Answers (1)
- Give one use of radioactive isotopes in industries.(Solved)
Give one use of radioactive isotopes in industries.
Date posted: March 29, 2019. Answers (1)
- 384g of radioactive element was reduced to 48g in 540 days. Determine the half-life of X.(Solved)
384g of radioactive element was reduced to 48g in 540 days. Determine the half-life of X.
Date posted: March 29, 2019. Answers (1)
- Study the table below and use it to answer the questions that follow.(Solved)
Study the table below and use it to answer the questions that follow.
(i) In which of the solution will phenolphthalein indicator be colourless.
(ii) Which of the solutions could be used to relieve heartburn? Explain.
Date posted: March 29, 2019. Answers (1)
- Study the reaction scheme below and answer the questions that follow.(Solved)
Study the reaction scheme below and answer the questions that follow.
(a) Write an ionic equation for the formation of the white precipitate.
(b) Write the formula of the complex ion present in the colourless solution Q.
Date posted: March 29, 2019. Answers (1)
- 100cm³ of sulphur (IV) oxide takes 20 seconds to diffuse through a porous plate. What volume of oxygen gas would diffuse through the same plate...(Solved)
100cm³ of sulphur (IV) oxide takes 20 seconds to diffuse through a porous plate. What volume of oxygen gas would diffuse through the same plate in 30 seconds under similar conditions. (S = 32, O = 16).
Date posted: March 29, 2019. Answers (1)
- Consider the following reaction at equilibrium.(Solved)
Consider the following reaction at equilibrium.
Complete the table below to show the effect of different factors on the position of equilibrium.
Date posted: March 29, 2019. Answers (1)
- In the down’s process (used for extraction of sodium) a certain salt is added to lower the melting point of sodium chloride from 8000C to...(Solved)
In the down’s process (used for extraction of sodium) a certain salt is added to lower the melting point of sodium chloride from 8000C to about 6000C.
(i) Identify the salt added.
(ii) Why is it necessary to lower the temperature?
(iii) Give one use of sodium.
Date posted: March 29, 2019. Answers (1)
- The set-up below shows how gas A was prepared and reacted with heated magnesium.(Solved)
The set-up below shows how gas A was prepared and reacted with heated magnesium.
(a) Give a reason why it is not advisable to heat magnesium before heating ammonium nitrite.
(b) (i) Identify gas A.
(ii) Write a chemical equation for the reaction between gas A and magnesium.
Date posted: March 29, 2019. Answers (1)