To find the molarity of sodium in the soup, we need to first convert the mass of sodium in the soup to moles. The atomic weight of sodium is 22.99 g/mol, so we can use the following conversion to find the number of moles of sodium in the soup:
moles Na = (890 mg Na) / (22.99 g/mol) = 38.8 moles Na
Next, we need to find the volume of the soup in liters. Since 4 cups is equal to 1 quart and 1 quart is equal to 0.946 liters, we can convert the volume of the soup from cups to liters using the following conversion:
volume (L) = (1 c) * (4 c/1 qt) * (0.946 L/1 qt) = 3.784 L
Finally, we can use the number of moles of sodium and the volume of the soup to calculate the molarity of sodium in the soup using the following formula:
molarity = (moles Na) / (volume (L)) = 38.8 moles Na / 3.784 L = 10.3 M
Therefore, the molarity of sodium in the soup is approximately 10.3 M.