Q1. In the reaction,
Be2C + xH2O → yBe(OH)2 +CH4
write the values of x and y.
Q2. Name the brown coloured gas evolved when lead nitrate crystals are heated in a dry test tube.
Q3. What is the difference between the following two reactions?
(i) Mg + 2HC1 → MgCl2 + H2
(ii) NaOH + HCl → NaCl + H2O
Q4. Double displacement reactions are also known as precipitation reactions. Why?
Q5. State one basic difference between a physical change and a chemical change.
Q6. Why is hydrogen peroxide kept in coloured bottles?
Q7. Zinc liberates hydrogen gas when reacts with dilute Hydrochloric Acid, whereas copper does not. Write the reason?
Q8. Aluminium is a reactive metal. But is still used for packing food articles. Write one reason for its use?
Directions (Q. Nos. 09-13) In the following questions a statement of Assertion is followed by a statement of Reason. Mark the correct choice as
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If Reason is true but Assertion ls false.
(e) If both Assertion and Reason are false.
Q9. Assertion: Chemical reaction changes the physical and chemical state of a substance.
Reason: When electric current is passed through water (liquid), it decomposes to produce hydrogen and oxygen gases.
Q10. Assertion: In a balanced chemical equation, total mass of the each element towards reactant side= total mass of the same element towards product side.
Reason: Mass can neither be created nor destroyed during a chemical change.
Q11. Assertion: When calcium carbonate is heated, it decomposes to give calcium oxide and carbon dioxide.
Reason: The decomposition reaction takes place on application of heat, therefore, its and endothermic reaction.
Q12. Assertion: Chips manufacturers usually flush bags of chips with gas such as nitrogen to prevent the chips from getting oxidised.
Reason: This increase the taste of the chips and helps in their digestion.
Q13. Assertion: Rusting of iron metal is the most common form of corrosion.
Reason: The effect of rusting of iron can be reversed if they are left open in sunlight.
Q14. Name and state the law which is kept in mind while we balance a chemical equation.
(a) Law of Equal Proportion
(b) Law of Conservation of Mass
(c) Daltons Law
(d) Avogadro’s Law
Q15. What is breaking and making of bonds in chemical reaction called?
(a) Chemical Reaction
(b) Chemical Equation
(c) Chemical Bonding
(d) Chemical Equilibrium
Q16. A red-brown gas is released along with O2 and lead oxide on heating lead nitrate. It is an example of
(a) combination reaction
(b) oxidation reaction
(c) decomposition reaction
(d) reduction reaction
Q17. What are the coefficients of the correctly balanced equation?
?Fe2O3 + ?CO → ?Fe+ ?CO2
(a)0, 2, 2,3
Q18· Burning of a candle is a
(a) physical change
(b) a chemical change
(c) slow change
(d) gaseous change