Monday, December 21, 2009

Help in basic chemistry and how to figure out the molarity in different solutions, such as ethanol?

A solution of ethanol in water is prepared by dissolving 75.0 mL of ethanol, C2H5OH (density = 0.79 g/cm3) in enough water to make 250.0 mL of solution. What is the molarity of the ethanol in this solution?Help in basic chemistry and how to figure out the molarity in different solutions, such as ethanol?
Convert mL of ethanol to g and then g to moles. Recall that cm^3 = mL.





75.0 mL ethanol x (0.79 g ethanol / mL) x (1 mole ethanol / 46.0 g ethanol) = 1.29 moles ethanol





Molarity = moles / L = 1.29 / 0.2500 = 5.2 MHelp in basic chemistry and how to figure out the molarity in different solutions, such as ethanol?
75.0 mL x 0.79 g/mL = 59.25 g C2H5OH


59.25 g / 46.07 g/mol = 1.2875 mol


1.2875 mol / 0.250 L = 5.150 M

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