a)When silver nitrate comes in contact with skin, it is reduced to white color metallic silver.In most cases, a black stain appears due to formation of finely divided silver which has black color.

The black color is due to the decomposition of the Ag+ ion into Ag, silver. Silver nitrate will slowly decompose with the silver ion reverting to elemental silver. The microscopic particles of silver are so small that they absorb light instead of reflecting it, and so appear black, instead of silver....

I think the best technique for memorizing is by assigning meaningfulness to things that are to be memorized.

Or in other words, relating things with a memorable story, simply, creating a story.
Do you remember yourself teaching us to memorize things easily. We had related words to a story and almost everyone in the class remembered at least 25 words among the total of 30. I still remember "Bhachyeko Haat". Haha!

Memory export Jim Kwik says that anything combined with emotion becomes a...

If one could be a billionaire by following a how-to guide step by step, you'd have already come across it by now. 

Well, the how-to "BE" part is simple; own anything that's worth a billion- an idea, an asset, a skill, anything. It is the how-to reach that milestone that is mystic. Carve your own path to it. 

Once you find the secret (IF there is one), share it on Mattrab :P 

Or maybe don't ;) let others find their own path.

In benzene molecule, carbon and carbon bond can't have polarity because there is not any electronegativity difference and the carbon hydrogen is also not much polar because the electronegativity difference is almost zero and also the small pull due to small difference in Electronegativity is balanced due to even pull from all directions.

In chlorobenzene the electronegativity difference between carbon and chlorine is very high so, it is polar.

(to compare polarity first check electronegativity...