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Use zinc powder which has larger surface area instead of zinc granules
johnmulu answered the question on February 15, 2017 at 08:33
- A dynamic equilibrium between dichromate and chromate ions is established as shown in the equation below(Solved)
A dynamic equilibrium between dichromate and chromate ions is established as shown in the equation below.
Cr2O$^{2-}_7$(aq) + 2OH-(aq) $^{\rightarrow}_{\leftarrow}$ 2CrO$_4^{2-}$(aq) + H2O(l)
a) What is meant by dynamic equilibrium?
b) State and explain the observation that would be made if a few pellets of potassium hydroxide are added to the equilibrium mixture.
Date posted: February 15, 2017. Answers (1)
- The decomposition of calcium carbonate can be represented by the equation:(Solved)
The decomposition of calcium carbonate can be represented by the equation:
CaCO3(s) $_{\rightarrow}^{\leftarrow}$ CaO(s) + CO2(g)
Explain how an increase in pressure would affect the equilibrium position.
Date posted: February 15, 2017. Answers (1)
- When bromine gas reacts with aqueous sodium hydroxide, the equilibrium represented by the equation:(Solved)
When bromine gas reacts with aqueous sodium hydroxide, the equilibrium represented by the equation:
Br2(aq) + 2OH-(aq) $_{\leftarrow}^{\rightarrow}$ Br-(aq) + OBr-(aq) + H2O(l) is established. What observations would be made if a few drops of sulphuric (VI) acid were added to the equilibrium mixture? Explain.
Date posted: February 15, 2017. Answers (1)
- What is meant by lattice energy?(Solved)
What is meant by lattice energy?
Date posted: February 15, 2017. Answers (1)
- State the Hess's Law and its applications(Solved)
State the Hess's Law and its applications.
Hess's law States that if a chemical change can be made to take place in two or more steps, the amount of the total heat change is the same no matter which method is used.
Its applications are:
1.Determination of heat of formation of substances which cannot be measured experimentally. Substances like methane,carbon dioxide and benzene cannot be prepared by uniting there elements. Therefore it is not possible to measure the heat of formation of certain compound directly.
2.Determination of heat of transition. The heat of transition from one allotropic form to another can also be calculated with the help of Hess's law.
3.Determination of heat of various reaction. By using Hess's law we can calculate enthalpies of many reactions which can not be measured directly. For example the enthalpy of dimerization of nitrogen dioxide.
Date posted: February 15, 2017. Answers (1)
- What is the meaning of molar heat of combustion?(Solved)
What is meant by molar heat of combustion?
Date posted: February 15, 2017. Answers (1)
- Write an ionic equation for the reaction that took place(Solved)
A beaker contained 75.0 cm3 of aqueous copper (II) sulphate at 23.7oC. When scrap iron metal was added to the solution, the temperature rose to 29.3oC.
Write an ionic equation for the reaction that took place
Date posted: February 15, 2017. Answers (1)
- What is the name given to each of the following:(Solved)
What is the name given to each of the following:
a) Ability of a metal to be made into wire
b) Minimum energy required for a chemical reaction to start;
c) Type of force that holds atoms of neon together?
Date posted: February 15, 2017. Answers (1)
- State one disadvantage of using hydrogen fuel instead of fossil fuels(Solved)
State one disadvantage of using hydrogen fuel instead of fossil fuels.
Date posted: February 15, 2017. Answers (1)
- State and explain two reasons why hydrogen is a very attractive fuel compared to fossils(Solved)
State and explain two reasons why hydrogen is a very attractive fuel compared to fossils.
Date posted: February 15, 2017. Answers (1)
- What is meant by molar heat of solution?(Solved)
What is meant by molar heat of solution?
Date posted: February 15, 2017. Answers (1)
- Define the standard enthalpy of formation of a substance(Solved)
Define the standard enthalpy of formation of a substance
Date posted: February 15, 2017. Answers (1)
- State two factors that should be considered when choosing fuel for cooking(Solved)
State two factors that should be considered when choosing fuel for cooking.
Date posted: February 15, 2017. Answers (1)
- Butane and propane are constituents of cooking gas. Which one produces more energy per mole on combustion?(Solved)
Butane and propane are constituents of cooking gas. Which one produces more energy per mole on combustion? Explain.
Date posted: February 15, 2017. Answers (1)
- When pure water is heated at 1 atmospheric pressure at sea level, the temperature of the water does not rise beyond 100oC(Solved)
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. Answers (1)
- Distinguish between exothermic and endothermic reaction(Solved)
Distinguish between exothermic and endothermic reaction.
Date posted: February 15, 2017. Answers (1)
- Explain why the enthalapy of neutralization of ethanoic acid with sodium hydroxide is different from that of hydrochloric acid with sodium hydroxide(Solved)
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. Answers (1)
- A compound whose general formula is M(OH)3 reacts as shown by the equation below(Solved)
A compound whose general formula is M(OH)3 reacts as shown by the equation below.
M(OH)3(s) + OH$^-_4$(aq) $\rightarrow$ M(OH)$^-_4$(aq)
M(OH)3(s) + 3H+(aq) $\rightarrow$ M3+(aq) + 3H2O(l)
a) What name is given to compounds which behave like M(OH)3 in the two reactions
b) Name two elements whose hydroxides behave like that of M.
Date posted: February 15, 2017. Answers (1)
- 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:(Solved)
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. Answers (1)
- 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(Solved)
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. Answers (1)