However, the thought behind this statement might be correct
, but this statement does not represent the correct mechanism that is actually required. Sodium does not have a free will to move around. It tends to move towards the compartment with a lower concentration because the probability increases of a sodium ion while it moves through a channel on the more concentrated side of the membrane and that the ion will move on the less concentrated side through a channel. In case you do not want to explain the principle that is behind osmosis, you may simply state the osmosis pressure that tends to drive sodium from the higher to a less concentrated side of a membrane.