Maybe not. Mixing ram isn't recommended. Sell your old ram and get either a 2x4gb or 2x8gb kit of cl9 1.5v 1600 ddr3. Craigslist, ebay, anandtech's for sale forum or your local listings are good places to sell.
im going to exchange them but if it possible to full 2 RAM sockets with 8 gb RAM memory one for each !