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With a 0.5 M solution: How many moles of NaCl would there be in 1,000 ml?

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I believe your question is meant to ask how many grams of NaCl would be needed to make a 0.5 M solution in 1,000 ml; if not, please message me.

By definition, you already know how many moles, because it is part of your question-- 0.5, or 1/2 mole. A 1 molar solution of a substance means one molecular weight of molecules in 1 liter, usually of water. One liter is equal to 1,000 milliliters, so we also have your final volume. A mole of a compound such as NaCl (salt) is defined as the sum of the molecular weights of each component (in grams) as we find on the Periodic Table. The molecular weight of NaCl is 58.44 grams. If we added that amount, it would be a one molar solution, but we want 1/2 molar. One half of 58.44g is 29.22 g. This is the amount of NaCl needed to make a 0.5 M solution. 

As a side note, when you make such a solution in labs, you would dissolve your salt in a bit less than 1,000 ml to start with. After the salt dissolves, you would bring the amount up to exactly 1,000 ml.


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