Express your answer to three significant figures

Question

a) A solution of rubbing alcohol is 69.9  (v/v) isopropanol in water. How many milliliters of isopropanol are in a 76.6  sample of the rubbing alcohol solution?

b) How many liters of a 3.27 solution are needed to provide 53.0 of (molar mass 174.01 )? Recall that is equivalent to mol/L

Answer 1

a) You didn't provide units for the 76.6 so I'll assume that it means 76.6 ml.

69.9 % (v/v) means 69 ml alcohol/100 ml of solution. Thus, 69.9 ml alc/100 ml soln x 76.6 ml = 53.5 ml alc.

b) You didn't provide units for the 3.27 nor for 53.0 so I'll assume they are M and grams respectively. See how important it is to include units, because when one assumes, ..... never mind.

53.0 g x 1 mol/174.01 g = 0.305 moles

(x L)(3.27 mol/L) = 0.305 moles

x = 0.0931 liters

If this is incorrect, it's because you didn't provide units.