An adult should have no more than 2568 mg of sodium per day. What is this limit in kilograms (kg) ?

2.568 * 10⁻³ kg

Explanation:

The amount of sodium to be taken by an adult is measured in terms of a limit, as given here.

That limit has been set as 2568 mg, when measured in milligrams.

The basic conversion from milligrams to g is done by dividing with 1000. Then 2568 milligrams will be 2.568 grams.

Now 100 grams are present in 1 kilogram.

So 2.568 grams are divided with 1000 to get the specified mass in kg.

The gives it as 2.568 * 10⁻³.