Answer:
0,218 moles
Step-by-step explanation:
I will first explain how many liters is 256ml, that is 0,256 l.
because the m stands for milli which is a factor of 1000 -> (256 ml / 1000 = 0,256 l)
To calculate the amount of moles you multiply the volume with the concentration. So 0,256l x 0,855M = 0,218 moles.