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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
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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
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The depth of the water in a rectangular swimming pool increases uniformly from 1M at the shallow
end to 3.5m at the deep end. The pool is 25m long and 12m wide. Calculate the volume of the pool
in cubic meters.
The pool is emptied by a cylindrical pipe of internal radius 9cm. The water flows through the pipe at speed of 3 metres per second. Calculate the number of litres emptied from the pool in two minutes to the nearest 10 litres. (Take π = 3.142)
Date posted:
March 29, 2019
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When 25cm³ of 0.5M HCl is added to 25cm³ of 0.5M NaOH the temperature of the solution rose from 230C to 260C. Given that the density of the solution is 1gcmˉ³ and its specific heat capacity is 4.2Jgˉ¹Kˉ¹.
(a) Determine the amount f heat evolved that caused the temperature rise.
(b) Work out the molar enthalpy of neutralization for this reaction.y is 4.2Jgˉ¹Kˉ¹.
Date posted:
March 29, 2019
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The set-up was used to prepare carbon (IV) oxide and investigate its properties.
(a) Write an equation for the reaction in vessel B.
(b) What is the role of sodium hydroxide solution in the set-up?
(c) What would be observed if a burning splint is introduced at jet C?
Date posted:
March 29, 2019
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A racing cyclist completes the uphill section of a mountain course of 75 km at an average speed of v km/hr. He then returns downhill along the same route at an average speed of (v + 20) km/hr. Given that the difference between the times is one hour, form and solve an equation in v.
Hence
a. Find the times taken to complete the uphill and downhill sections of the course.
b. Calculate the cyclists average speed over the 150km.
Date posted:
March 29, 2019
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State and explain the main reasons why businesses exists.
Date posted:
March 29, 2019
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20cm³ of a dibasic acid required 25cm³ of 0.1M NaOH for complete neutralization.
(a) How many moles of sodium hydroxide reacted with the dibasic acid?
(b) Calculate the concentration of the dibasic acid in moles per litre.
Date posted:
March 29, 2019
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0.92g of ethanol were found to burn in excess air producing a temperature rise of 32.5oC in 200cm3 of water(C=12.0,H=1.0,O=16.0) Density of water is 1g/cm3, specific heat capacity of water is 4.2KjKg-1K-1.
(a) Write the equation for the combustion of ethanol.
(b) Determine the molar heat of combustion of ethanol
Date posted:
March 29, 2019
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The diagram below shows electrolysis of dilute copper (II) sulphate solution using copper electrodes;
a) State the observations made at electrode A and B
b) Write the equation of reaction at electrode A
Date posted:
March 29, 2019
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Below is a simplified process for manufacture of sodium carbonate by Solvay process.
a) Name substance M.
b) Name the process taking place in step II.
c) Write an equation for the reaction in step III.
d) What is the fate of ammonium chloride in the solvay process.
Date posted:
March 29, 2019
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Using dots (.) and crosses (x) to represent electrons, show the bonding in hydroxonium ion (H=1 O=8).
Date posted:
March 29, 2019
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In an experiment, two pieces of iron sheets were wrapped in each case with zinc and copper metal sheets as shown below.They were left in the open for some months.
State and explain the observations made in the experiments; (I), (II)
Date posted:
March 28, 2019
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Name the following processes;
a) When anhydrous calcium chloride is left in an open beaker overnight a solution was formed.
b) When sodium carbonate decahydrate crystals are left in an open beaker for some days it turned into a powder.
Date posted:
March 28, 2019
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60cm³ of oxygen gas diffused through a porous hole in 50 seconds. How long will it take 80cm³ of sulphur (IV) oxide to diffuse through the same hole under the same conditions (S = 32, O = 16).
Date posted:
March 28, 2019
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Starting with solid lead (II) carbonate, briefly describe how a sample of lead (II) chloride can be prepared.
Date posted:
March 28, 2019
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a) Explain why hydrogen gas has been replaced by helium in filling aeroplane tyres.
b)Hydrogen gas is bubbled through oil in presence of a catalyst to yield fats.
(i) Name a suitable catalyst used in the above process.
(ii) What name is given to the above process.
Date posted:
March 28, 2019
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4. 9 g a tribasic acid was dissolved in water and the solution made up to 500cm3. If the molarity of the hydrogen ions in the solution is 0.3 molar calculate the relative molecular mass of the acid.
Date posted:
March 28, 2019
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The diagram below represents pipes used in Frasch pump for the extraction of sulpur
Name the substance that pass through the following tubes and the direction which they flow.
1.
2.
3.
Date posted:
March 28, 2019
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12.0 cm3 of methane and 48cm3 of oxygen were exploded together. The final volume measured under the original conditions was 36.0 cm3 neglecting the water formed. 24.0cm3 of this was unused oxygen. Show the ratio of reacting volume of the gases referred to and gaseous products formed.
Date posted:
March 28, 2019
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Element X contains isotopes with mass number 16 and 18 respectively existing in the ratio
1: 3. Calculate the relative atomic mass of X.
Date posted:
March 28, 2019
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What volume of methane would remain if a burner containing 40cm³ of methane burns in 40cm³ of enclosed air
(assuming that oxygen is 20% of air)?
Date posted:
March 28, 2019
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A compound has empirical formula C3H6O and relative formula mass of 116. Determine it’s molecular formula.(C = 12, H = 1, O = 16).
Date posted:
March 28, 2019
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The scheme below shows some reaction of salt. Study it and answer questions that follow.
(i) Write an equation for the reaction to show formation of gas P and solid X.
(ii) Give the name and formula of the complex ion responsible for the deep blue colour in the solution.
Date posted:
March 28, 2019
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Explain why potassium chloride conducts electricity in both the molten state and in aqueous solution whereas hydrogen chloride conducts electricity only in aqueous solution and not in gaseous state.
Date posted:
March 28, 2019
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An element E has relative atomic mass of 69.39. Given that the element has two isotopes of atomic masses 62.35 and 70.45, calculate the relative abundance of each of the isotopes.
Date posted:
March 28, 2019
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Name the method of separation that can most suitably be used to separate the following mixtures.
(a) Gasoline from petroleum
(b) Benzoic acid and potassium carbonate
(c) Oil from cashew nuts
Date posted:
March 28, 2019
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25.0cm3 of 0.12M potassium hydroxide solution required 30.0cm3 of a solution of a dibasic acid (H2Y) for complete neutralization. The acid contained 3.15g per 500cm3 solution.
Calculate:
(a) The molarity of the acid solution
(b) The relative formula mass of the acid.
Date posted:
March 28, 2019
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A Student in form four placed a thermometer in molten naphthalene at 850C and recorded the temperature and time until the naphthalene solidified. From the values obtained, the figure below was drawn.
(a) What name is given to such a figure?
(b) Which part of the figure represents the change of state of naphthalene?
(c)In terms of kinetic theory. Explain what happens to molecules along AB.
Date posted:
March 28, 2019
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The table below shows information about three solid substances A, B and C. Study it and answer the question that follow.
Describe how you will separate the three solids from a mixture of the three.
Date posted:
March 28, 2019