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Q. 3. Redraw the diagram given in your answer book and show the direction of the light ray afterreflection from the mirror.
Ans
Q. 4. What is meant by a saturated hydrocarbon? 1
Ans. A saturated hydrocarbon is a hydrocarbon in which the carbon atoms are connected by only a single bond.
Q. 5. Chlorine, bromine and iodine form a Dobereiner’s triad. The atomic masses of chlorine and iodine are 35·5 and 126·9 respectively. Predict the atomic mass of bromine. 1
Ans.
| Element of the triad | Symbol | Atomic masses |
| 1. Chlorine | Cl | 35·5 |
| 2. Bromine | Br | ? |
| 3. Iodine | I | 126·9 |
According to Dobereiner’s triad, the atomic mass of bromine is the arithmetic mean of Cl and I.
Atomic mass of Br = 
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CBSE 2009 Question Papers Class X