Question

A student weights out 635.94 g Na2CO3 and dissolved it in 2.0 L water. What is the molarity of his solution?

Answer 1

2.3 moles / L

Step-by-step explanation:

Answer 2

You have to find out the number of moles of the substance.

I will use rounded numbers for the atomic weights because every periodic table is different.

2Ca = 2 * 40 = 80

1 C = 1 * 12 = 12

3O = 3 * 16 = 48

Atomic Mass = 140

moles = given mass / molar mass

moles = 635.94 / 140

moles = 4.54

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Now you need to find the concentration

C = moles / Volume in liters.

C = 4.54/ 2.0 L

C = 2.27 moles / L

Technically since the volume is only 2 significant digits, your answer should be 2.3 moles / L

If you do not have this as a choice, what are your choices.