molar mass?

Question

what is the molarity of a solution containing 56g.of solute in 959 mL. of solution? (molar mass of solute= 26g/mol)

what is the molarity of 200mL of solution in which 2.0 moles of sodium bromide is dissolved?

Answer 1

take the mass of the solute (56g) and divide it by the molar mass (26g)

(56g/26g)= Moles of Solute

then use the equation:

Molarity = (moles solute)/(Liters of Solution)
M=(n)/(V)

in this situation
Molarity = [(56g/26g)/(.959L)
Molarity = 2.2
Don't Forget to use sig figs

the second problem goes the same way, just remember to use
M=(n)/(V)

don't forget to change the units of mL to Liters.

The Molar mass is simply the weight of 1 mole of the compound. just add up the weights of the atoms (NaBr) like this

One atom of Na = 22.9amu
One atom of Br = 79.9amu

since the compound NaBr only has one of each we add them together without multiplying

(22.9 + 79.9) = 102.8 = Molar Mass of NaBr

once again the molar mass is simply how many grams of a said compound to make 1 mole of that compound. I'll let you figure the rest out.

Answer 2

Molarity = moles/liters (make sure you always use "liters" for the volume).

In the first problem you have to first change grams to moles. You do this by dividing by the molar mass.

You now have "moles" and you have "liters" (if you change mL to liters). Just substitute into the Molarity formula.

In the second problem you have "moles", you have "liters" (if you change mL to liters). Just substitute into the Molarity formula.

Answer 3

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