Final answer:
To make a 5.0 L solution of 2.0 M NaCl, approximately 3.33 L of 3.0 M NaCl is needed. The closest option is 4.0 L.
Step-by-step explanation:
To find out how many liters of 3.0 M NaCl are needed to make a 5.0 L solution of 2.0 M NaCl, we can use the formula:
M1V1 = M2V2
Where M1 and V1 are the initial concentration and volume, and M2 and V2 are the final concentration and volume. So, plugging in the values:
(3.0 M)(x L) = (2.0 M)(5.0 L)
3x = 10
x = 10/3 = 3.33 L
Therefore, approximately 3.33 L of 3.0 M NaCl is needed to make up a 5.0 L solution of 2.0 M NaCl. Since the answer options are given in whole numbers, the closest option would be 4.0 L.