Question

Please show how to do each step

LAB: Mass Percent

1-Weigh approximately 5 g NaCl on weigh paper and add to a 250 ml Erlenmeyer flask. Record the exact mass here (The mass is 4.85 g )

2-Using a 100 ml graduated cylinder, add 100 ml water to the flask and stir until the solute has dissolved. Calculate the concentration in mass percent of this solution assuming the density of the water is 1 g/ml.

Solution + flask =227.747 g

Flask =81.565 g

3-Transfer 60.0 ml of the NaCl solution using a 100 ml graduated cylinder to a PREVIOUSLY weighed 150 ml beaker. The mass percent of the solution in the beaker is _______________.

The beaker mass is 93.469 g

4-Weigh the beaker with the 60 ml solution sample and record the mass here _153.623 g. Calculate the mass of solution as well as the mass of solute in the beaker.

5-Transfer 40.0 ml of the NaCl solution from the Erlenmeyer flask to a PREVIOUSLY weighed 150 ml beaker. Don’t forget to weigh the beaker before adding the NaCl solution to it. Record the mass of the beaker is 93.495 g. The mass percent of this solution in the beaker is _______________.

6-Weigh the beaker with the solution and record the mass here 133.790 g. Calculate the mass of solution as well as the mass of solute in the beaker.

7-Compare the masses of the solutions and solutes in each beaker (calculated values in numbers 4 and 6) with their respective concentrations.

Answer 1

In number 2 there is an inconsistency, if you added 100mL of water to the flask the differenc of the weight of solution + flask and flask should be close to 100 (227.747g-81.565g=146.182g), I'll eliminate this for the calculation.

2) If you added 4.85 g of salt to 100mL or 100g of water the mass percent should be:

<----since you do not have the actual mass of the solution, because of above explanation I am assumig the mass of the solution is 100g from the water plus 4.85 from the salt.

3) 4.62% <---is the same solution as in the first flask

4) the mass of solution is:

the mass of solute is:

5) as in number 3), 4.62% <---is the same solution as in the first flask

6) the mass of solution is:

the mass of solute is:

7) Basically you are trying to prove, that the sum of the masses of the solute en each beaker should be the initial mass:

The calculations did not yield the exact mass from the beginnig because of weighing errors or probably because of the actual initial mass of the solution as I mentioned above.