School of elements.
1. Which scientist stated the “Law of Triad”? (Dobereiner)
2. Who introduced the “Law of Octaves”? (Newlands)
3. What was Mendeleev’s basis for the classification of elements? (atomic mass)
4. The unknown element of Mendeleev’s periodic table, Eka – Aluminium was later named as (gallium)
5. How many elements are there in the 4thand 5th period of modern periodic table? (18)
6. Halogens belongs to which group in Modern Periodic Table? (seventeenth)
7. Which is the longest period in Modern Periodic table? (sixth)
8. What is the valency of first group elements? (one)
9. Transition elements belong to which block in modern periodic table? (d)
10. Zero group elements exist in which physical state at ordinary temperature? (gaseous)
11. Which element has electronic configuration 2,8,2? (Mg)
12. The electronic configuration of element ‘y’ is 2,7. What is its valency?(one)
13. What happens to atomic size of elements on moving from left to right in a period?(decreases)
14. What are normal elements? (s and p block elements)
15. The element x belongs to group five. What is the number of valence electrons in x? (five)
16. In which period the element ‘x’ belongs, if its electronic configuration is 2, 8, 1? (third)
17. What is the valency of the element with atomic number 17? (one)
18. Which block elements have last three shells incompletely filled? (f)
19. Sulphur, carbon, iodine belongs to which block in Modern periodic table? (p)
20. Which element has twice as many electrons in its second shell as its first shell? (carbon)
21. A, B and C are the elements of Doberener’s triad. If the atomic mass of A is 40 and that of C is 137. What would be the atomic mass of B? (88.5)
22. The element A belongs to which group it is atomic number if 23? (fifth group)
The Magic of Chemical Reactions
1. What happens when silver chloride is exposed to sunlight?(silver metal is formed)
2. What is the chemical formula of Plaster of Paris (POP)? (CaSO4. H2O)
3. What happens during reduction reaction? (reactants gain hydrogen)
4. What is called the addition of oxygen to a substance? (oxidation reaction)
5. What is the odour of H2S gas? (rotten egg)
6. What type of chemical reaction take place when magnesium wire is burnt in air? (combination reaction)
7. What type of chemical reaction takes place when lime stone is heated? (decomposition reaction)
8. How are food products containing fats and oils are packaged in order to prevent from spoilage? (nitrogen)
9. When soap is scrubbed on a white cloth, where a yellow stain of curry is present, it changes into reddish brown. This is due to: (neutralization reaction)
10. Silver ornaments become dark on prolonged exposure to air. This is due to the formation of layer of its. (sulphide)
The acid base chemistry
1. The colour of universal indicator solution is: (greenish yellow)
2. The substance which is bitter to taste is: (an alkali)
3. A student measured the PH values of four solutions marked A, B, C and D found them to be 6, 12, 2 and 14 respectively. The solution which is likely to be strongly acidic is: (C)
4. What is the pH value of neutral solution? (7)
5. What colour change takes place when phenolphthalein is added to NaOH solution? (pink)
6. What is the taste of acidic substances? (sour)
7. Acids turn blue litmus into: (red)
8. What is litmus paper? (natural indicator)
9. What do all acids contain? (hydrogen)
10. Give the chemical formula for baking soda. (NaHCO3)
11. What is the common name for sodium hydrogen carbonate? (Baking soda)
12. Which salt is used to disinfect water? (bleaching power)
13. A solution in test tube A has pH less than seven, which kind of solution it is? (acidic)
14. Which colour does the methyl orange indicator give in basic solution?(yellow colour)
15. Name the plant from which Litmus solution is extracted. (Lichen)
16. Which salt is used to reduce acidity in stomach? (baking soda)
17. Which salt is used in manufacturing paper? (sodium carbonate)
18. Name the salt which makes hard water soft? (Na2CO3)
19. Which salt is used in fire extinguisher? (NaHCO3)
20. The carboxylic acid present in milk is: (Lactic acid)
21. What is milk of magnesia? (magnesium hydroxide)
The electric spark
1. When current is plotted against potential difference, a straight line plot is obtained, which of the following law is verified? (Ohm’s law)
2. When the resistance of the conductor increases then the current will: (decrease)
3. Keeping the potential difference constant the resistance of the circuit is made four times. How much does the current change? (becomes one fourth)
4. If the resistance is to be increased then the number of resistances should be connected in: (series)
5. What is the equivalent resistance of three resistances of 2 ohms, 3 ohms and 4 ohms are connected in series? (9 ohms)
6. In series combination which remains constant? (current)
7. You are given three equal resistances, in how many combinations can they be arranged? (four)
8. Which instrument is used to measure electric current? (ammeter)
9. Which instrument is used to measure potential difference? (voltmeter)
10. Which physical quantity has the unit ohm? (resistance)
11. Which combination is used to decrease resistance in the circuit? (Parallel)
12. How would the three resistance of 3 ohms each be connected so as to produce an equivalent resistance of 1 ohm. (all in parallel)
13. If we want to connect a large number of electric bulbs for decorating buildings which circuit is better? (series)
14. Keeping the potential difference constant, the resistance of the circuit is doubled. By how much does the current change? (half)
15. Which particles constitute the electric current in a metallic conductor? (electrons)
16. What is the SI unit of electric charge? (coulomb)
17. What is the SI unit of electric current? (Ampere)
18. Who invented battery? (Alessandro Volta)
19. Which metal has lowest resistivity? (silver)
20. What is the commercial unit of electrical energy? (kilowatt – hour)
21. By what other name is the unit Joules / Coulomb called? (volt)
22. What is the SI unit of resistivity? (ohm – metre)
23. Which of the following is a best conductor of electricity? (silver)
24. Which is the allow of Cu and Ni? (constantan)
25. Which material is used to make filament of an electric bulb? (tungsten)
26. Which device work on the principle of heating effect of electric current. (fuse)
27. Which substance has infinitely high resistance? (rubber)
28. What is the resistivity of silver? (1.60 x 10 – 8 ohm m)
29. How is electric power calculated? (electric power = potential difference x current)
30. What material is used in electric iron as a heating element? (nichrome)