a) mCl2 = 2 * 35.5 = 71
mNaCl = 23 + 35.5 = 58.5
71gCl2.......................117gNaCl
x...........................177 rezulta x = 107.41gCl2
b) mMgCl2 = 24 + 71 = 95g/mol
4moli = 95 * 4 = 380
71gCl2.........................95gMgCl2
y...........................380 rezulta y = 284gCl2