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When pure water is heated at 1 atmospheric pressure at sea level, the temperature of the water does not rise beyond 100oC, even with continued heating. Explain this observation
Date posted:
February 15, 2017
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Explain why the enthalapy of neutralization of ethanoic acid with sodium hydroxide is different from that of hydrochloric acid with sodium hydroxide.
Date posted:
February 15, 2017
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When magnesium burns in air, it forms a white solid and a grey-green solid. When a few drops of water are added to the mixture, a gas that turns red litmus paper blue is evolved.
Identify the:
i) White solid
ii) Gas evolved and the gas
I) Name of gas
II) Use of the gas.
Date posted:
February 15, 2017
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Naturally occurring magnesium consists of three isotopes. 78.6%24Mg; 10%25Mg and 26Mg. Calculate to one decimal place, the relative atomic mass of magnesium.
Date posted:
February 15, 2017
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Describe how sodium carbonate is used to remove water hardness.
Date posted:
February 15, 2017
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Dissolving of potassium nitrate in water is an endothermic process. Explain the effect of increase in temperature on the solubility of potassium nitrate.
Date posted:
February 15, 2017
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Starting with zinc sulphate solution, describe how a sample of zinc oxide can be obtained.
Date posted:
February 15, 2017
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Aqueous hydrogen chloride reacts with potassium manganate (VII) to produce chlorine gas, while a solution of hydrogen chloride in methylbenzene has no effect on potassium manganate (VII). Explain this observation.
Date posted:
February 15, 2017
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A sample of river water is suspected to contain zinc and sulphate ions. Describe how the presence of zinc ions and sulphate ions can be established.
Date posted:
February 15, 2017
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In an experiment using a ripple tank the frequency, f, of the electric pulse generator was reduced to one third of its value. How does the new wavelength compare with the initial wavelength? Explain your answer.
Date posted:
February 14, 2017
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State Ohm's Law.
Date posted:
February 14, 2017
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In large current circuits large resistors in parallel are preferred to low resistors in series. Explain.
Date posted:
February 14, 2017
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State two reasons why the efficiency of a pulley system is always less than 100%.
Date posted:
February 14, 2017
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A cyclist initially at rest moved down a hill without pedaling. He applied brakes and eventually stopped. State the energy changes as the cyclist moved down the hill.
Date posted:
February 14, 2017
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A crane lift a load of 2000 kg through a vertical distance of 3.o m in 6 seconds.Determine the:
i) Work done
ii) Power development by the crane
iii) Efficiency of the crane given that it is operated by an electric motor rated 12.5 KW.
Date posted:
February 14, 2017
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If a load on 100 N is raised by applying an effort of 28 N, determine the efficiency of the system.
Date posted:
February 14, 2017
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A body of mass M is allowed to slide down an inclined plane. State two factors that affects its final velocity at the bottom of the incline.
Date posted:
February 14, 2017
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A horizontal force of 12N is applied on a wooden block of mass 2 kg placed on a horizontal surface. It causes the block to accelerate at 5 ms-2. Determine the frictional force between the block and the surface.
Date posted:
February 14, 2017
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A car of mass 30 kg is pushed along a horizontal path by horizontal force of 8 N and moves with a constant velocity. The force is then increased to 14N. Determine:
a) The resistance to the motion of the cart;
b) The acceleration of the cart.
Date posted:
February 14, 2017
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A trolley is moving at a uniform speed along a track. A piece of plasticine is dropped on the trolley and sticks on it. Explain why the trolley slows down.
Date posted:
February 14, 2017
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A high jumper usually lands on thick soft mattress. Explain how the mattress helps in reducing the force of impact.
Date posted:
February 14, 2017
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An industrial trolley of mass 20 kg carrying a mass of 50 kg is acted on by a constant force. The trolley moves along a horizontal smooth surface with an acceleration of 0.5 ms-2. Determine the acceleration of the trolley after the mass falls off.
Date posted:
February 14, 2017
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A gun is fired vertically upwards from the top of an open truck moving horizontally, uniform velocity of 50ms-1. The bullet achieves a maximum height of 45 m.
i) State with reason whether or not the bullet will land on the truck
ii) Calculate the distance covered by the truck just before the bullet reaches the level from which it was fired. (Use g = 10 ms-2)
Date posted:
February 14, 2017
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A trolley is moving at constant speed in friction compensated track. Some plasticine is dropped on the trolley and sticks on it. State with a reason what is observed about the motion of the trolley.
Date posted:
February 14, 2017
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A small object lies at the bottom of a water pond at a depth of 1.2 m. Given that the refractive index of water is 1.3, Determine the apparent depth of the object. (Give your to 1 decimal place)
Date posted:
February 14, 2017
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A ball of mass 200 g is thrown vertically upwards with velocity of 5 ms-1. The air resistance is 0.4 N. Determine:
i) The net force on the ball as it moves up;
ii) The acceleration of the ball;
iii) The maximum height reached by the ball,
(take acceleration due to gravity g = 10 ms-2)
Date posted:
February 14, 2017
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A trolley moving on a horizontal bench of height 1.2 m, strikes a barrier at the edge of the bench. The brass mass on the top of the trolley flies off on impact and lands on the ground 2.5 m from the edge of the bench. Determine:
i) The time taken by the brass mass to reach the ground
ii) The speed at which the trolley struck the barrier.
Date posted:
February 14, 2017
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A matatu starts from rest and accelerates to cover a distance of 49 m in 7 seconds. Determine:
i) Its acceleration;
ii) Its velocity after 7 seconds
Date posted:
February 14, 2017
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A sample of fertilizer is suspected to be calcium ammonium nitrate. Describe chemical test for each of the following ions in the sample:
a) Calcium ions
b) Ammonium ions.
Date posted:
February 13, 2017
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Name two methods that can be used to remove permanent hardness from water.
Date posted:
February 13, 2017