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(a) Explain, with an example, how the physical states of the reactants and products can be shown in a chemical equation.
(b) Balance the following equation and add state symbols :
Zn + HCl ——– > ZnCl2 + H2
(c) Convey the following information in the form of a balanced chemical equation :
“An aqueous solution of ferrous sulphate reacts with an aqueous solution of sodium hydroxide to form a precipitate of ferrous hydroxide and sodium sulphate remains in solution.”
(a) The physical
states of the reactants and products are shown by putting the “state symbols”
in an equation.
For example: Zn (s) + H2SO4 (aq) —–> ZnSO4 (aq) + H2(g)
b) Zn (s) + 2HCl(aq) —–> ZnCl2 (aq) + H2 (g)
(c) FeSO4(aq)+ 2NaOH (aq) —–> Fe(OH)2 (s) + Na2SO4(aq)
Write any two observations in an activity that may suggest that a chemical reaction has taken place. Give an example in support of your answer.
(a) Aluminium hydroxide reacts with sulphuric acid to form aluminium sulphate and water. Write a balanced equation for this reaction.
(b) Balance the following chemical equation :
MnO2 + HCl —–> MnCl2 + Cl2 + H2O
(a) 2Al(OH)3+ 3H2SO4 —–> Al2(SO4)3+ 6H2O
(b) MnO2+ 4HCl —–> MnCl2+ Cl2 + 2H2O
Write the balanced equations for the following reactions, and add the state symbols (a) Magnesium carbonate reacts with hydrochloric acid to produce magnesium chloride, carbon dioxide, and water.
(b) Sodium hydroxide reacts with sulphuric acid to produce sodium sulphate and water.
(a) MgCO3 (s) + 2HCl (aq) MgCl2 (aq) + CO2 (g) + H2O (l)
(b) 2NaOH (aq) + H2SO4 (aq) Na2SO4 (aq) + 2H2O (l)
Carbon monoxide reacts with hydrogen under certain conditions to form methanol (CH3OH). Write a balanced chemical equation for this reaction indicating the physical states of reactants and product as well as the conditions under which this reaction takes place.
The conditions for this reaction to take place are a pressure of 300 atmospheres (written as 300 atm), a temperature of 300oC, and a catalyst which is a mixture of zinc oxide and chromium oxide (ZnO + CrO3).
(a) Potassium chlorate (KClO3) on heating forms potassium chloride and oxygen. Write a balanced equation
for this reaction and indicate the evolution of gas.
(b) Rewrite the following information in the form of a balanced chemical equation :
Magnesium burns in carbon dioxide to form magnesium oxide and carbon.
(s) 2KCl (s) + 3O2 (g)
(b) 2Mg + CO2 —–> 2MgO + C
(a) Substitute formulae for names and balance the following equation :
Calcium carbonate reacts with hydrochloric acid to produce calcium chloride, water, and carbon dioxide gas.
(b) Write a balanced chemical equation with state symbols for the following reaction: Sodium hydroxide solution reacts with a hydrochloric acid solution to produce sodium chloride solution and water.
(a) CaCO3+ 2HCl —–> CaCl2 + H2O + CO2
(b) NaOH (aq) + HCl(aq) —–> NaCl (aq) + H2O (l)
Ammonia reacts with oxygen to form nitrogen and water. Write a balanced chemical equation for this reaction. Add the state symbols for all the reactants and products.
4NH3 (g)+ 3O2 (g) —–> 2N2 (g) + 6H2O (l)
Write a balanced chemical equation for the process of photosynthesis giving the physical states of all the substances involved and the conditions of the reaction.
6CO2 (g) + 6H2OC6 —–> H12O6 (aq) + 6O2(g)
Translate the following statement into a chemical equation and then balance it :
Barium chloride solution reacts with aluminium sulphate solution to form a precipitate of barium sulphate and aluminium chloride solution.
3BaCl2(aq) + Al2(SO4)3 (aq) —–> 3BaSO4 (s) + 2AlCl3(aq)
When potassium nitrate is heated, it decomposes into potassium nitrite and oxygen. Write a balanced equation for this reaction and add the state symbols of the reactants and products.
2KNO3 (s) —–> 2KNO2 (s) + O2(g)
(a) What is meant by a chemical reaction? Explain with the help of an example.
(b) Give one example each of a chemical reaction characterized by :
(a)Chemical reactions are the processes in which new substances with new properties are formed.
For example: When magnesium ribbon is heated, it burns in air to form a white powder called magnesium oxide.
(b)The chemical reaction between zinc and dilute sulphuric acid.
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(a) State the various characteristics of chemical reactions.
(b) State one characteristic each of the chemical reaction which takes place when :
(a) The various characteristics of chemical reactions are:
(b) Evolution of carbon dioxide gas
(a) What do you understand by exothermic and endothermic reactions ?
(b) Give one example of an exothermic reaction and one of an endothermic reaction.
(c) Which of the following are endothermic reactions and which are exothermic reactions ?
(a) Those reactions in which heat is evolved are known as exothermic reactions.
The reactions in which heat is absorbed are known as endothermic reactions.
(b) Example of exothermic reaction:
C (s) + O2 (g) —–> CO2 + Heat
Example of endothermic reaction:
N2 (g) + O2 (g) + Heat —–> 2NO (g)
(c) Endothermic reactions: Photosynthesis, Electrolysis of water, Decomposition of calcium carbonate.
Exothermic reactions: Burning of natural gas, Respiration.
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When the solution of substance X is added to a solution of potassium iodide, then a yellow solid separates out from the solution.
(a) What do you think substance X is likely to be ?
(b) Name the substance which the yellow solid consists of.
(c) Which characteristic of chemical reactions is illustrated by this example ?
(d) Write a balanced chemical equation for the reaction which takes place. Mention the physical states of all the reactants and products involved in the chemical equation.
(a) Lead nitrate.
(b) Lead iodide.
(c) Formation of a precipitate.
(d) Pb(NO3)2 (aq) + 2KI (aq) —–> PbI2 (s) + 2KNO3 (aq)
When water is added gradually to a white solid X, a hissing sound is heard and a lot of heat is produced forming a product Y. A suspension of Y in water is applied to the walls of a house during white washing. A clear solution of Y is also used for testing carbon dioxide gas in the laboratory.
(a) What could be solid X ? Write its chemical formula.
(b) What could be product Y ? Write its chemical formula.
(c) What is the common name of the solution of Y which is used for testing carbon dioxide gas ?
(d) Write chemical equation of the reaction which takes place on adding water to solid X.
(e) Which characteristic of chemical reactions is illustrated by this example ?
(a) Calcium oxide, CaO.
(b) Calcium hydroxide, Ca(OH)2
(c) Lime water.
(d) CaO + H2O —–> Ca(OH)2
(e) Change in temperature.
When metal X is treated with a dilute acid Y, then a gas Z is evolved which burns readily by making a little explosion.
(a) Name any two metals which can behave like metal X.
(b) Name any two acids which can behave like acid Y.
(c) Name the gas Z.
(d) Is the gas Z lighter than or heavier than air ?
(e)Is the reaction between metal X and dilute acid Y exothermic or endothermic ?
(f) By taking a specific example of metal X and dilute acid Y, write a balanced chemical equation for the reaction which takes place. Also indicate physical states of all the reactants and products.
(a) Zinc and Iron.
(b) Dilute hydrochloric acid and dilute sulphuric acid.
(d) Lighter than air.
(f) Suppose metal X is zinc (Zn) and acid Y is dilute hydrochloric acid (HCl) ;
Zn (s) + 2HCl (aq) ZnCl2 (aq) + H2 (g)
A solid substance P which is very hard is used in the construction of many buildings, especially flooring. When substance P is heated strongly, it decomposes to form another solid Q and a gas R is given out. Solid Q reacts with water with the release of a lot of heat to form a substance S. When gas R is passed into a clear solution of substance S, then a white precipitate of substance T is formed. The substance T has the same chemical composition as starting substance P.
(a) What is substance P ? Write its common name as well as chemical formula.
(b) What is substance Q ?
(c) What is gas R ?
(d) What is substance S ? What is its clear solution known as ?
(e) What is substance T ? Name any two natural forms in which substance T occurs in nature.
(a) Calcium carbonate (limestone), CaCO3
(b) Calcium oxide, CaO
(c) Carbon dioxide, CO2
(d) Calcium hydroxide, Ca(OH)2; Lime water.
(e) Calcium carbonate; Limestone and Marble.