how many anions in this?

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How many anions are in 0.500 g of MgBr2

Oran Armstrong · Accepted Answer

An example of poorly taught chemistry, but first the answer:A mole is just a number chemists use to describe weight. This many atoms of any element equals its atomic weight in the periodic table. Molecular weight is the sum of atomic weight. For example 1 mole of MgBr2 is 24.3 + 2*80 = 184.3 grams/mole. 0.5 grams would be 0.5 g / (184.3 g/mole) = 0.00271 moles. The actual value of a mole is 6.02E23, using scientific notation. The number of ions can be deduced by writing a chemical formula describing how Magnesium bromide forms ions:MgBr -> Mg(+2) + 2Br(-)The negative ions (Bromine) are the anions. Since moles are just numbers, molecular ratios are the same as mole ratios. 1 mole of MgBr2 forms 2 moles of Bromine anions. The number of ions is therefore 2(2.71E-3)(6.02E23) = 3.266E21 anions.Why this is bad chemistry : No (sane) chemist I've ever met counts atoms, ions or angels dancing on the heads of pins. The concept of the mole is fundamental to chemistry, but the number itself is rarely - if ever - used. Chemistry teachers who force their students to count atoms do this science a great disservice.

Jace Toy DDS

how many anions in this?

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