First, to mindless1, the OP, MY APOLOGIES! I made a serious error in my first post, and I only found it because jayabansal got such a different answer I had to find out why.

My major error was I read the exponent of my calculations wrong, and found the answer IF the Ka for Ascorbic acid had been 6.76 x 10^(-6). BUT it is supposed be 10^(-5)! So, doing it my way properly, my answer should have been that the initial concentration of Ascorbic acid should be 0.0158 Moles per litre, and that comes to 2.78 g of Ascorbic acid powder per litre of solution. I was off by a whopping factor of 10 almost!

Now, that still does not agree exactly with jayabansal, and there are two reasons. To start, I searched for values for Ka and found various values from sources I expected to be reliable. The one I used, from the Merck Index, says pK1 = 4.17, so 10^(-4.17) = 6.76 x 10^(-5). Another says at 10C the pKa = 4.7, so Ka = 10^(-4.7) = 2.00 x 10^(-5). A third says pKa = 4.10, and hence Ka = 7.94 x 10^(-5). Quite a range! If we use my calculation process but jayabansal's value of 8.0 x 10^(-5), my process says the answer is 0.0135 Molar, or 2.38 grams dry Ascorbic acid powder.

The other difference is in the process details. As i said in my fist post, the formula I used insisted on including the fact that a small amount of the original Ascorbic acid placed in the solution is NOT in its original state. It is dissociated, and hence the denominator in my formula uses the unknown "y" for the original amount and subtracts off the amount "lost" by dissociation. This makes for a messy bunch of algebra that I evaded by having a spreadsheet do the work and trying successive approximations until I got the value for y that gave the target result for Ka. jayabansal, on the other hand, made use of the approximation commonly used that the amount dissociated is quite small and should be ignored in the calculation. If you do that, and use the 8.0,,, etc. value for Ka, the simplified calculation process yields an initial Ascorbic acid concentration of 0.0125M, or 2.20 grams of dry powder as jayabansal got. Note that using that approximation yielded results that differ only a little: 2.38 g versus 2.20 g. That's why people feel justified in simplifying with that approximation technique in the calculation.

Bottom line: I made a significant error, and jayabansal's post has prompted me to find and correct it. So depending on which value of Ka one believes, and on whether or not one uses the simplifying approximation in the calculation, the answer is between 2.78 g and 2.20 g of dry powder. Most of that range is due to the variability of reference data for the value of pKa.