### OF CLASS 10 SCIENCE .

#### SOLVE THIS QUESTIONS TO CHECK YOUR CONCEPT OF CHEMISTRY POSITION

1.Write the balanced chemical equations for the following and identify the type of chemical
reactions.
(i) Hydrogen iodide on reacting with chlorine gas gives iodine and hydrochloric acid.
(ii) Methane gas burns in oxygen of air to form  carbon dioxide and water.
(ii) On passing electric current through molten  aluminium oxide, it decomposes to form
aluminium metal and oxygen gas.

2.Write chemical equations for the reaction  taking place when
(i) Sodium  reacts with dilute HNO3
(ii) Sodium reacts with water.
(iii) Zinc reacts with dilute hydrochloric  acid.

3.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
(i) neutral
(ii) strongly alkaline
(iii) strongly acidic
(iv) weakly acidic
(v) weakly alkaline?
Arrange the pH in increasing order of H* ion   concentration.

4.Show the formation of MgO by the transfer of electrons in the two elements using electron dot structures.

5. P, Q and R are 3 elements which undergo chemical reactions according to the following equations:

(a) $P_{2}O_{3}&space;+&space;2Q&space;\rightarrow&space;Q_{2}O_{3}&space;+&space;2P$

(c) $3RO+&space;2P\rightarrow&space;P_{2}O_{3}&space;+&space;3R$

(1) Which element is most reactive?
(11) Which element is least reactive?
(iii) State the type of reaction listed above.

6. (i) Write any two properties of ionic  compounds.
(ii) Show the formation of aluminium chloride by the transfer of electrons between the atoms. (Atomic number of aluminium and chlorine are 13 and 17 respectively).

7. Explain the reactions of different metals with hot water, cold water and steam. Give one
example with a proper balanced chemical equation. Name two metals which do not react with any form of water.

8.A metal A, which is used in thermite process, when heated with oxygen gives an
oxide B which is amphoteric in nature. Identify A and B. Write down the reactions
of oxide B with HCl and NaOH.

9.What is meant by electrolytic reduction? How is sodium obtained from its molten
chloride? Explain.

10.An element A reacts with water to form a compound B which is used in white washing. The compound On heating forms an oxide C which on treatment with water gives back B. Identify A, B and C and give the reactions involved.

11.Give reasons for the following:
(i) Ionic compounds have higher melting and boiling points.
(ii) Sodium is kept immersed in kerosene.
(iii) Reaction of calcium with water is less violent.
(iv) Prior to reduction the metal sulphides and carbonates must be converted into metal
oxides for extracting metals.

12.How is copper obtained from its ore(Cu2S)? Write only the chemical equations. How is copper thus obtained refined? Name and explain the process alongwith a labelled diagram.

13.In what forms are metals found in nature With the help of examples, explain how metals react with oxygen, water and dilute acids. Also, write chemical equations for the reactions.

14."Carbon tetrachloride is not a good conductor of electricity". Give reason to justify this statement.

15.Name the compound formed when ethanol is heated in excess of concentrated sulphuric acid at 443 K. Also write the chemical equation of the reaction stating the role of concentrated sulphuric acid in it. What would happen, if hydrogen is added to the product of this reaction in the presence of catalyst such as palladium or  nickel?

16.An aldehyde as well as a ketone can  be represented by the same molecular formula, say C3H6O. Write their structures  and name them. State the relation between the two in the language of science.

17.(i).Name the property of ethanol which makes it useful in medicine.
(ii) Name the organic compound which is used pickles. Mention its in composition.
(iii) Mention any two uses of alcohol in medicine.

18.An organic compound A is a constituent of many medicines and used as an antifreeze and has the molecular  formula C2H6O. Upon reaction with alk. KMnO4, the compound A is oxidised to
another compound B with formula C2H4O2. Identify the compounds A and B. Write the chemical equation for the reaction which leads to the formation of B.

19.An organic compound A on heating with conc. H2SO4 ;forms a compound B which on addition of one mole of hydrogen in presence of Ni forms a compound C. One mole of compound C, on combustion forms two moles of CO2 and three moles of H2O. Identify the compounds A, B and C, write the chemical equation of the reactions involved.

20.A compound X is formed by the reaction of a carboxylic acid C2H4O2 and an alcohol in the presence of a few drops of H2SO4.The alcohol on oxidation with alk. KMnO4  followed by acidification gives the same carboxylic acid as used in this reaction. Give the names and structures of
(i) carboxylic acid,
(ii) alcohol and
(iii) thecompound X. Also write the reaction.

21.(i)Give a chemical test to distinguish between saturated and unsaturated hydrocarbon.
(ii) Name the products formed when ethane burns in air. Write the balanced chemical equation for the reaction showing the types of energies liberated.
(iii) Why is reaction between methane and chlorine in the presence of sunlight considered a substitution reaction?

22.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.

23. (i) 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.
(i) Name the scientist who first of all showed that atomic number of an element is a more fundamental property than its atomic mass.
(iii) State modern periodic law.

24.Consider two elements A (atomic number =17) and B (atomic number = 19)
(i) Write the positions of these elements in  the modern periodic table giving justification.
(ii) Write the formula of the compound  formed when A combines with B.
(iii) Draw the electron dot structure of the compound and state the nature of the bond formed between the two  elements.

25.Two elements P and Q belong to the 3rd period of the modern periodic table and are in group 1 and group 2, respectively. Compare their following characteristics in tabular form:
(i) The number of electrons in their atoms
(ii) The sizes of their atoms
(iii) Their metallic character
(iv) Their tendencies to lose electrons
(v) The formula of their oxides
(vi) The formula of their chlorides

26.Three elements X, Y and Z have atomic numbers 7, 8 and 9 respectively.
(i) State their positions (group number and period number both) in the modern periodic table
(ii)Arrange these elements in the decreasing order of their atomic radii.
(iii) Write the formula of the compound formed when X combines with Z.

27.Atoms of seven elements A, B, C, D, E, F and G have different number of electronic
shells but have the same number of electrons in their outermost shells. How will the following property vary as we move from A to G?
(i) Metallic character
(iii) Valency.

28.Differentiate ethanol and ethanoic acid on the basis of physical and chemical property.

29.explain the action of soap and detergent in hard water ?

30.An element Y has a total of three shells, with six electrons in its valence shell.
(i) What will be the atomic number of this element?
(ii) In which period will you find this element?
(iii) Name another element which belongs to the same group as this element.