0.252 M
First figure out how much calcium sulfate you have. You do this by multiplying the volume of solution you have by its concentration.
0.734 L * 1.13 moles/L = 0.82942 moles
Now figure out the volume of fluid you will have after diluting. Just simply add the volumes together.
0.734 L + 2.56 L = 3.294 L
Finally, divide the number of moles you have by the new volume
0.82942 moles / 3.294 L = 0.251797 moles/L
Round to 3 significant figures giving 0.252 M
