CHEMICAL REACTIONS AND EQUATIONS
Q1. Define rancidity. What kind of substances are used to prevent rancidity? Explain any three methods to prevent rancidity.
Q2. You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dil. HCl, dil. HNO3 and H2O. In which of the above containers can these solutions be kept?
Q3. Write balanced chemical equations for the following reactions:
(i) NaOH solution is heated with zinc granules.
(ii) Excess of Carbon Dioxide gas is passed through lime water.
(iii) Dilute Sulphuric Acid reacts with sodium carbonate.
(iv) Egg shells are dropped in Hydrochloric Acid.
(v) Copper (II) Oxide reacts with dilute Hydrochloric Acid.
Q4. A compound ‘X’ on heating with excess Conc. Sulphuric Acid at 443 K gives an unsaturated compound ‘Y’, ‘X’ also reacts with sodium metal to evolve a colourless gas ‘Z’. Identify ‘X’, ‘Y’ and ‘Z’. Write the equation of the chemical reaction of formation of ‘Y’ and also write the role of Sulphuric Acid in the reaction.
Q5. Consider the Chemical equation given below and answer the questions that follow.
ZnO + C → Zn + CO
(a) Name the substance which is getting oxidised.
(b) Name the substance which is getting reduced.
(c) Name the oxidising agent.
(d) Name the reducing agent.
(e) What type of a reaction does this equation represent?
Q6. With the help of an activity, demonstrate how do we know that a chemical reaction has taken place?
ACIDS, BASES AND SALTS
Q1. Give one example in each case:
(i) A basic oxide which is soluble in water.
(ii) A basic oxide which is insoluble in water.
(iii) A weak mineral acid.
(iv) A base which is not an alkali.
(v) A hydrogen-containing compound which is not an acid.
Q2. (i) What is meant by pH?
(ii) Two solutions A and B have pH values of 3.0 and 9.5 respectively. Which of these will turn litmus solution from blue to red and which will turn phenolphthalein from colourless to pink?
(iii) Water is a neutral substance. What colour will you get when you add a few drops of universal indicator to a test tube containing distilled water?
Q3. A metal carbonate X on heating with acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at the anode during electrolysis of brine is passed on dry Y, it gives a compound Z, used for disinfecting drinking water. Identify X, Y, G and Z.
Q4. (i) Bee-sting leaves a chemical substance that causes pain and irritation. Name the chemical substance. Identify the type of substance which may give relief on the sting area when applied on it.
(ii) Mention the pH value below which tooth decay begins. How this fall below this value? Explain the ill effect of the acidic medium in the mouth. How can this be prevented?
(iii) What are strong acids and weak acids? Give an example of each
Q5. (a) Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively. Which solution is:
(iii) strongly acidic
(ii) strongly alkaline
(iv) weakly acidic
(v) weakly alkaline?
Arrange the solutions in increasing order of H+ ion concentration.
(b) Name the acid and base from which the following salts have been formed.
(i) Sodium Acetate
(ii) Ammonium Chloride
Q6. (i) Dry pellets of a base ‘X’, when kept in open, absorbs moisture and turns sticky. The compound is also formed by Chloro-alkali process. Write the chemical name and formula of X. Describe chloro-alkali process with a balanced chemical equation. Name the type of reaction that occurs when X is treated with dilute hydrochloric acid. Write the chemical equation.
(ii) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
Q7.Give suitable reasons for the following statements:
(i) Rainwater conducts electricity but distilled water does not.
(ii) We feel burning sensation in the stomach when we overeat.
(iii) A tarnished copper vessel regains its shine when rubbed with lemon.
(iv) The crystals of washing soda change to white powder on exposure to air.
(v) An aqueous solution of sodium chloride is neutral but an aqueous solution of sodium carbonate is basic.
Q8. (i) Write the chemical name and chemical formula of washing soda.
(ii) How is it obtained from sodium chloride? Give equations of the reaction.
(iii) Why is it called a basic salt? Give its anyone use.
Q9. Answer the following:
(i) What happens when a concentrated solution of sodium chloride is electrolysed? Write the equation of the reaction involved.
(ii) Why is the electrolysis of a concentrated solution of sodium chloride known as Chlor- alkali process?
(iii) Name three products of the Chlor-alkali process. State two uses of each product.
METALS AND NON-METALS
Q1. (i) Predict the reaction, if any, between
(a) Zinc and Silver Nitrate solution,
(b) Magnesium and Iron (II) Chloride solution,
(c) Copper and Magnesium Sulphate solution.
Write the equations, with its physical form symbols, for the reaction.
(ii) A lump of element X can be cut by a knife. During its reaction with water, X floats and melts. What is X? Explain.
Q2. (a) Define the terms ‘alloy’ and ‘amalgam’. Name the alloy used for welding electric wires together. What are its constituents?
(b) Name the constituents of the following alloys:
(i) Brass (ii) Stainless steel (iii) Bronze,
State one property in each of these alloys, which is different from its main constituents.
Q3. (i) Name the method used to extract metals of high reactivity.
(ii) Name the main ore of mercury. How is mercury obtained from its ore? Give balanced chemical equations.
(iii) Explain what is thermite reaction with the help of balanced equation. How is it used to join railway tracks or cracked machine parts?
Q4. (a) An ore on treatment with dilute hydrochloric acid produces brisk effervescence. What type of ore is this? Write the steps required to obtain metal from the enriched ore.
(b) An ore on heating in air gives sulphur dioxide gas. Name the method in each metallurgical step, that will be required to extract this metal from its ore.
Q5. Give reason for the following :
(a) Ionic compounds have high. melting and boiling points.
(b) Non-metals, in general, do not displace hydrogen from dilute acids.
(c) Hydrogen gas is not evolved, when zinc metal reacts with dil. HNO3
(d) School bells are made up of metals.
(e) Oxides of highly reactive metals cannot be reduced by carbon.
Q6. (i) An ore, on heating in air, give sulphur dioxide gas. Name the method in each metallurgical step, that will be. required to extract this metal from its ore.
(ii) State which of the following reactions will take place or which will not, giving suitable reason for each?
Zn(s)+CuSO4 (aq) → ZnSO4 (aq)+Cu(s)
Fe(s) + ZnSO4 (aq) → FeSO4 (aq) + Zn(s)
CARBON AND ITS COMPOUNDS
Q1. Define structural isomer and draw the isomeric structures of butane. Compare the structure of benzene and cyclohexane by drawing them.
Q2. What is the difference between combustion and oxidation? Under what condition an oxidation reaction can be called as combustion? Illustrate your answer with one example in each case.
Q3. (i) State the litmus test to distinguish between an alcohol and a carboxylic acid.
(ii) Give the equation for the reaction of a carboxylic acid with an alcohol. State the condition for the reaction and name the product formed. What is this reaction known as?
(iii) Write a reaction which is reverse of this reaction? Mention the conditions required for the reaction. Name and write the use of this reaction.
Q4. An organic compound A is widely used as a preservative in pickles and has a molecular formula C2H4O2 . This compound reacts with ethanol to form a sweet-smelling compound B.
(i) Identify the compound A
(ii) Write the chemical equation for its reaction with ethanol to form compound B.
(iii) How can we get compound A from B?
(iv) Name the process and write corresponding chemical equation.
(v) Which gas is produced when compound A reacts with washing soda? Write the chemical equation.
Q5. Why are certain compounds called hydrocarbons? Write the general formula for homologous series of alkanes, alkenes and alkynes and also draw the structure of the first member of each series. Write the name of the reaction that converts alkenes into alkanes and also write a chemical equation to show the necessary conditions for the reaction to occur.
Q6. (a)Draw the structure for the following compounds:
(ii) 2-methyl propane,
(b) Draw the electron dot structure for ethanoic acid.
Q7. List two reasons for carbon forming a large number of compounds. Name the type of bonding found in most of its compounds. Why does carbon form compounds mainly by this kind of bonding. Give reason why the carbon compounds:
(i) Generally have low melting and boiling points.
(ii) Do not conduct electricity in molten state.
Q8. Soaps and detergents are both types of salts. State the difference between the two. Write the mechanism of the cleansing action of soaps. Why do soaps not form lather (foam) with hard water? Mention any two problems that arise due to the use of detergents instead of soaps.
Q9. What are micelles? Why does it form when soap is added to water? Will a micelle be formed in other solvents such as ethanol also? State briefly how the formation of micelles help to clean the clothes having oily spots.
Q10. A compound A (C2H4O2) reacts with Na metal to form a compound ‘B’ and evolved a gas which burns with a pop sound. Compound ‘X on treatment with an alcohol ‘C’ in presence of an acid forms a Sweet smelling compound ‘D’ (C4H8O2). On addition of NaOH to ‘D’ gives back Band C. Identify C and D write the reactions involved.
Q11. A carbon compound ‘P’ on heating with excess conc. H2SO4 forms another carbon compound ‘Q’ which on the addition of hydrogen in the presence of nickel catalyst forms a saturated carbon compound ‘R’. One molecule of ‘R’ on combustion forms two molecules of carbon dioxide and three molecules of water. Identify P, Q and R and write chemical equations for the reactions involved.
Q12. Make the structure of methane by showing sharing of electrons between carbon and hydrogen atoms. How could you convert methane into chloroform by substitution reaction? Explain with the help of chemical reactions.
Q13. (a) A compound X with molecular formula, C2H4 burns with a sooty flame. It decolourises bromine water. Identify X. Will it dissolve in water or not? Will it conduct electricity in aqueous solution?
(b) An organic compound X is an essential constituent of-wine and beer, which is responsible for intoxication caused by these drinks. Oxidation of X yields an organic acid Y, which is present in vinegar. Name the compounds X and Y.
Q14. (a) An element of group 14 has two common allotropes, A and 8. A is very hard and is bad conductor of electricity while 8 is soft to touch and good conductor of electricity. Identify the element and its allotropes. Explain reasons for their different properties.
(b) How can we distinguish ethanoic acid and ethanol using their chemical properties? Write any three differences.
Q15. How are the following pairs related?
(i) 2, 2-dimethylpropane and 2-methylbutane
(ii) Ethane and propane
(iii) C2H5Cl and C3H7Cl
(iv) C3H4 and C2H4
Q16 . Draw the structures of
(iv) Sodium Ethanoate
(v) Butanoic Acid
(vii) Sodium Ethoxide
(viii) Sodium Stearate
(x) Sodium Acetate
Q17. Give account of chemical properties?
(i) combustion of ethanol
(ii) oxidation of ethanol
(iii) reaction of C2H5OH with sodium metal
(iv) dehydration of C2H5OH
(v) reaction of C2H5OH with ethanoic acid
Q18. An organic compound A with molecular formula C4H8O2 on alkaline hydrolysis gives two compound B and C. C on acidification with dil. HCl gives D. Oxidation of B with K2Cr2O7/H2SO4 also gives D. Identify A, B, C and D and explain all the reactions involved.
CLASSIFICATION OF ELEMENTS
Q1. Mendeleev’s predicted the existence of certain elements not known at that time and named two of them as Eka-silicon and Eka-aluminium.
(i) Name the elements which have taken the place of these elements.
(ii) Mention the group and the period of these elements in the modern periodic table.
(iii) Classify these elements as metals, non-metals or metalloids.
(iv) How many valence electrons are present in each one of them?
Q2. What is meant by group in the modern periodic table? How do the following changes occur on moving from top to bottom in a group?
- Number of valence electrons
- Number of occupied shells
- Size of atoms
- Metallic character of element
- Effective nuclear charge experienced by valence electrons
Q3. Consider two elements A (atomic number = 17) and B (atomic number= 19)
- Write the positions of these elements in the modern periodic table giving justification.
- Write the formula of the compound formed when A combines with B.
- Draw the electron dot structure of the compound and state the nature of the bond formed between the two elements.
Q4. An element is placed in 2nd group and 3rd period of the periodic Table, burns in presence of oxygen to form a basic oxide.
- Write the electronic configuration.
- Write a balanced equation when it burns in the presence of air.
- Write a balanced equation when this oxide is dissolved in water.
- Draw the electron dot structure for the formation of this oxide. \
- Identify the element.
Q5. (i) Why do we classify elements?
(ii) What are the two criteria used in the development of Modern Periodic Table?
(iii) State the position of
(b) non-metals and
(c) metalloids in the periodic table.
(iv) Would you place two isotopes of chlorine; Cl-35 and Cl-37 in different slots of the periodic table because of their different atomic masses or in the same slot because their chemical properties are same? Justify your answer.
Q6. (a) Why did Mendeleev have gaps in his periodic table?
(b) State any three limitations of Mendeleev’s classification?
(c )How do electronic configurations of atoms change in a period with an increase in atomic number?
Q7. (a) What was the basis of Mendeleev’s classification of elements?
(b) List two achievements of Mendeleev’s Periodic table.
(c) List any two observations which posed a challenge to Mendeleev’s Periodic Law.
Q8. (a) The modern periodic table has been evolved through the early attempts of Dobereiner, Newland and Mendeleev. List one advantage and one limitation of all the three attempts.
(b) Name the scientist who first of all showed that atomic number of an element is a more fundamental property than its atomic mass.
Q9. Explain giving justification the trends in the following properties of elements, on moving from left to right in a period, in the Modern Periodic Table:
(a) Variation of valency.
(b) Change of atomic radius.
(c) Metallic to non-metallic character.
(d) Electronegative character.
(e) Nature of oxides.
Q10. (a) An element which is an essential constituent of all organic compounds belongs to which group?
- Account for the following:
- Elements of group 18 are called zero-valent.
- If an element X is placed in group 14, what will be the formula and the nature of bonding of its chloride?
- An element X forms a chloride with formula XCI3. The element X would most likely be in the same group of the periodic table as for which of the following
- Na, Mg, AI or Ca.
- Elements of which groups will form acidic oxides?
Q11. (a) Consider the following elements:
Na (11), AI (13), Cl (17), K (19)
For the given elements, find out
(i) valency (ii) period number (iii) group number
(b) An element X belongs to group 17 and element Y belongs to group 1. What type of bond will they form?
Q11. The positions of five elements in the periodic table are shown below:
What are the number of valence electrons in B? Identify the element(s) which
(i) will have the. smallest atomic radius?
(ii) will be the most metallic?
(iii) will form basic oxide?
(iv) will show valency three?
(v) will show greatest tendency to gain electron?