Q1. Balance the following chemical equation:
Pb(NO3)2(s) ─heat→ PbO(s) + NO2 (g) + O2 (g)
Q2. Write a balanced chemical equation for the reaction between sodium carbonate and hydrochloric acid indicating the physical state of the reactants and the products.
Q3. Name a reducing agent that may be used to obtain manganese from manganese dioxide.
Q4. Why do potato chips manufacturers fill the packet of chips with nitrogen gas?
Q5. What is the valency of silicon with atomic number 14?
Q6. Fresh milk has a pH of 6. When it changes into curd (yoghurt) will its pH value increase or decrease? Why?
Q7. During the summer season, a milkman usually adds a very small amount of baking soda to fresh milk. Give one reason.
Q8. A drop of litmus solution is added to each of the four solutions given below. State the colour of litmus solution observed in each: soap solution, sodium carbonate solution, vinegar, lemon juice.
METALS & NON-METALS
Q9. The surface of some metals loses their brightness when kept in air for a long time. Why?
Q10. What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes?
Q11. Metals generally occur in the solid state. Name and write symbol of a metal that exists in a liquid state at room temperature.
Q12. Write a balanced chemical equation to represent the following reaction: Iron reacts with stream to form Iron (II, III) oxide with hydrogen gas.
Q13. State two characteristic features of carbon which when put together give rise to a large number of carbon compounds.
Q14. Write the structural formula of chloroethane.
Q15. Draw the electron-dot structure of ethane molecule (C2H6).
Q16. Write the number of horizontal rows in the modern periodic table. What are these rows called?
Q17. Write the name and formula of the 2nd member of homologous series having general formula CnH2n.
Q18. Name the process of converting vegetable oil to vegetable ghee.
Q19. Write the molecular formula of (i) Methane and (ii) Ethanol.
Q20. Write the name of the first two members of homologous series having a functional group –OH.
Q21. Butanone is a four-carbon per molecule compound. Note the functional group present in it.
Q22. State Modern Periodic Law of classification of elements.
Q23. The atomic number of sodium is 11, fluorine is 9 and neon is 10. Why are sodium and fluorine very reactive while neon shows almost no reactivity.