s. (20 points) In a laboratory experiment, a 10.0 mL. sample of NaCl solution is

Question

s. (20 points) In a laboratory experiment, a 10.0 mL. sample of NaCl solution is poured into an evaporating dish with a mass of 24.10 g. The combined mass of the evaporating dish and NaCI solution is 36.15 g. After heating, the evaporating dish and dry NaCI have a combined mass of 25.50 g. NaCI solution. W Determine the mass percent (m/m) of the hat is the molarity (M) of the NaCI Solution. If water is added to the 10.0 mL of the initial NaCI solution to give a final volume of 60.0 mL, what is the molarity of the dilute NaCl solution?. In another case in the laboratory a solution is prepared with 70.0 g of HNOs and 130.0 g of H20. The HNOs solution has a density of 1.21 g/mL. What is the mass percent (m/m) of the HNO3 solution. What is the total volume, in milliliters, of the solution. What is the total mass per volume (m/v) of the solution and finally determine the molarity (M) of the solution.

Explanation / Answer

Mass of 10 ml solutionof NaCl+ dish= 36.15 gm

Mass of dish= 24.10 gm

Mass of NaCl solution = mass of 10ml sample + mass of dish –mass of dish= 36.15-24.10 = 12.05 gm

Mass of dish and combined mass after drying =25.5 gm

Mass of water evaporated = mass of 10ml solution of NaCl+ dish- (mass of dry NaCl+ mass of dish)

=36.15-25.5= 10.65 gm

Mass of dry NaCl = mass of NaCl solution- mass of water evaporated= 12.05-10.65 =1.4 gm

Mass % of NaCl in the sample =100* mass of dry NaCl/ mass of NaCl solution = 100*1.4/12.05=11.62%

Molarirty= moles of solute ( NaCl)/ Liter of solution

Mass of NaCl= 1.4 gm, moles of NaCl= mass/molar mass= 1.4/58.5=0.024moles

Volume of solution = 10ml, 1000ml= 1L, 10ml= 10/1000L=0.01L

Molarity= 0.024/0.01=2.4M

Since M1V1= M2V2

Where M1= 2.4M, V1= 10ml, V2= 60ml

M2= M1V1/V2= 2.4*10/60=0.4M

2.

Mass of HNO3= 70 gm, mass of water =130 gm

Mass of solution containing HNO3 and water= 70+130=200gm

Mass % of HNO3 =100* mass of HNO3/ total mass= 100*70/200= 35%

Volume of solution = maass of solution/density= 200/1.21 ml=165.3ml,

Mass % of HNO3/volume= 100*70/165.3 =42.35%

Molarity =moles of HNO3/ liter of solution

Moles= mass of HNO3/ molar mass = 70/63=1.11

Volume of solution in L= 165.3/1000=0.1653 L

Molarity= 1.11/0.1653=6.71M

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