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Half-life is the time required for a quantity to reduce to half its initial value.
MICHAELONYINKWA answered the question on September 19, 2017 at 14:35
- A student burnt magnesium ribbon in a gas jar full of sulphur (IV) oxide gas.
(i) State two observations made in the gas jar
(ii) Write an...(Solved)
A student burnt magnesium ribbon in a gas jar full of sulphur (IV) oxide gas.
(i) State two observations made in the gas jar
(ii) Write an equation for the reaction that took place
Date posted: September 18, 2017. Answers (1)
- A student fetched water from a river in a limestone area. He used it for washing and
realized that it did not lather easily.
(i) Name the...(Solved)
A student fetched water from a river in a limestone area. He used it for washing and
realized that it did not lather easily.
(i) Name the two ions that prevent lathering
ii)Given that the structure of soap is C17H35COONa.Explain by means of ionic equations how the above ions prevent lathering
Date posted: September 18, 2017. Answers (1)
- 5.0g of calcium carbonate were allowed to react with 25cm3 of 1.0M hydrochloric acid until there was no further reaction. Calculate the mass of calcium...(Solved)
5.0g of calcium carbonate were allowed to react with 25cm3 of 1.0M hydrochloric acid until
there was no further reaction. Calculate the mass of calcium carbonate that remained
unreacted(Ca = 40, C = 12, O = 16).
Date posted: September 18, 2017. Answers (1)
- Study the following equilibrium equation
2X2(g) + Y2(g)<------> 2X2Y(g) H = -197kJ/mol
Suggest two ways of increasing the yield of X2Y(Solved)
Study the following equilibrium equation
2X2(g) + Y2(g)<------> 2X2Y(g) H = -197kJ/mol
Suggest two ways of increasing the yield of X2Y
Date posted: September 18, 2017. Answers (1)
- Give two physical properties of hydrogen gas(Solved)
Give two physical properties of hydrogen gas
Date posted: September 18, 2017. Answers (1)
- (a) Proteins are obtained from amino acids monomers. Complete the equation below to show the polymer formed.
H2NCH2COOH + H2NCHCH3COOH ---------->H2O +---------
b)Name the type of polymerization...(Solved)
(a) Proteins are obtained from amino acids monomers. Complete the equation below to show the polymer formed.
H2NCH2COOH + H2NCHCH3COOH ---------->H2O +---------
b)Name the type of polymerization shown above
Date posted: September 18, 2017. Answers (1)
- Dry carbon (II) oxide gas was passed over heated lead (II) oxide.
(a) Write an equation for the reaction
(b) Give one industrial application of the above...(Solved)
Dry carbon (II) oxide gas was passed over heated lead (II) oxide.
(a) Write an equation for the reaction
(b) Give one industrial application of the above reaction.
(c) Name another gas that can be used in the above reaction.
Date posted: September 18, 2017. Answers (1)
- Explain the effects of the accumulation of nitrogenous compounds in water masses?(Solved)
Explain the effects of the accumulation of nitrogenous compounds in water masses?
Date posted: September 18, 2017. Answers (1)
- State two conditions that would make the boiling point of water to be higher than 100oC(Solved)
State two conditions that would make the boiling point of water to be higher than 100oC
Date posted: September 18, 2017. Answers (1)
- a)Why is the percentage of carbon(IV)oxide in the atmosphere fairly constant? (b)Calculate the volume of carbon(IV)oxide in 8,000 m3 of air contained in a hall.(Solved)
a)Why is the percentage of carbon(IV)oxide in the atmosphere fairly constant?
b)Calculate the volume of carbon(IV)oxide in 8,000 m3 of air contained in a
Date posted: September 18, 2017. Answers (1)
- Which two elements will react more vigorously with each other between fluorine, neon, sodium, magnesium?(Solved)
Which two elements will react more vigorously with each other between fluorine, neon, sodium, magnesium?
Date posted: September 17, 2017. Answers (1)
- Define the term a mole?(Solved)
Define the term a mole?
Date posted: September 16, 2017. Answers (1)
- Electrical conductivity decreases when temporary hard water is heated. Explain(Solved)
Electrical conductivity decreases when temporary hard water is heated. Explain
Date posted: September 14, 2017. Answers (1)
- a)State the Faraday’s law of electrolysis
b)Calculate how long it would take an aqueous gold (III) chloride cell to coat 2.5 g of gold
on a...(Solved)
a)State the Faraday’s law of electrolysis
b)Calculate how long it would take an aqueous gold (III) chloride cell to coat 2.5 g of gold
on a bracelet using a current of 2.5 A. The half reaction has been provided for you.
c)Two half-cells are connected under standard conditions to make an electrochemical cell.
The two half-cells are a copper-copper (I) ion (Cu/Cu+) and an aluminum-aluminum ion (Al/Al3+). Using your the Standard Reduction Potentials below answer.
Al3+(aq) + 3e- → Al(s) -1.66 V
Cu2+(aq) + e- → Cu(s) 0.52 V
i)Write the cell diagram for the cell obtained when the two half cells are connected
ii)Identify which reaction is the anode and which is the cathode.
(iii)Calculate the emf for the cell
(iv)Write the overall balanced redox reaction for the electrochemical cell
d)An excess of copper solid is dropped into a solution which contains AgNO3 , Fe (NO3)3 and Zn (NO3)2. Write the ionic equations for any reduction half cell-reactions that occur over time under standard conditions
Date posted: September 14, 2017. Answers (1)
- a)Given that the mass of copper obtained in an o extraction was 210kg, determine the percentage purity of the ore used (copper pyrites) if 810kg...(Solved)
a)Given that the mass of copper obtained in an o extraction was 210kg, determine the percentage purity of the ore used (copper pyrites) if 810kg of it was fed to the 1st roasting furnace. (Cu = 63.5, Fe = 56, S = 32.0)
b)Give 2 effects that the process above could have on the environment.
Date posted: September 14, 2017. Answers (1)
- A student found a bottle containing CH3CH2COOCH3.
(i)Name the process of formation of the substance above
ii)Identify the two substances from which the substance above is derived...(Solved)
A student found a bottle containing CH3CH2COOCH3.
(i)Name the process of formation of the substance above
ii)Identify the two substances from which the substance above is derived .
iii)Give one advantage and one disadvantage of using soapless detergent
iv)Explain briefly how the soapless detergents given above may be manufactured
Date posted: September 14, 2017. Answers (1)
- Write down the equation for the reaction between Ethene and hydrogen when equal numbers of moles are used.(Solved)
Write down the equation for the reaction between Ethene and hydrogen when equal numbers of moles are used.
Date posted: September 14, 2017. Answers (1)
- Explain how ethane and ethene can be distinguished by burning(Solved)
Explain how ethane and ethene can be distinguished by burning
Date posted: September 14, 2017. Answers (1)
- a) Explain how a catalyst affects the activation energy during chemical reaction. (b)In an experiment to determine the heat of combustion of methanol. CH3OH, a student...(Solved)
A) Explain how a catalyst affects the activation energy during chemical reaction.
B)In an experiment to determine the heat of combustion of methanol. CH3OH, a student was recorded the following requirement the following data
Volume of water =100cm3
Final temperature of water = 22.00c
Initial temperature of water = 36.00c
Final mass of lamp an methanol = 84.75g
Initial mass of lamp and methanol=85.10g
Density of water = 1 g/cm3
(S.H.C of water = 4.23 g-1K-1)
i)Write an equation for the combustion of methanol
(ii) Calculate:
(a) Number of moles of methanol used in this experiment
(b) The heat change for this experiment
(c) The heat of combustion per mole of methanol
(d) Explain why the molar heat of combustion for methanol obtained above is different from the theoretical value.
(e) State two factors to consider when choosing a fuel.
(f) Outline two disadvantages of using hydrogen as a source of fuel.
Date posted: September 14, 2017. Answers (1)
- a)Using ionic equation explain how sodium carbonate can be used to soften hard water.(b)Other than softening of hard water give 2 other uses of sodium...(Solved)
a)Using ionic equation explain how sodium carbonate can be used to soften hard water.
b)Other than softening of hard water give 2 other uses of sodium carbonate.
Date posted: September 14, 2017. Answers (1)