The label on a tub of margarine states that 100 g of the margarine contains 0·70 g of sodium. the sodium is present as sodium chloride. calculate the mass of sodium chloride, in grams, present in a 10 g portion of the margarine. the mass of one mole of sodium chloride, nacl, is 58·5 g.

This problem requires three conversions: 1) mass of margarine to mass of sodium, 2) mass of sodium to moles of sodium, and finally 3) moles of sodium to grams of sodium chloride (since moles of Na = moles of NaCl).

1) mass of Na = 10g marg • (0.70g Na / 100g marg)

2) moles of Na = mass of Na • (1 mol Na / 22.99g Na)

3) mass of NaCl = moles of Na • (58.5g NaCl / 1 mol NaCl)

Combining all three steps:

mass of NaCl = 10g • (0.70g / 100g) • (1 mol / 22.99g) • (58.5g / 1 mol) = 0.18g NaCl

If we check the units, we find that our final answer should be in units of grams, which it is.

It would be true sodium reacts with water in a violent way 

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