Question

1. Ifyou wanted to make a 4 M NaCl solution and you wanted a full Liter of it, how would you make it? Describe all of the steps. (Remember from lab, molecular weight of NaCl is 58.44) 2. Now describe how you would dilute this 4 MNaCl solution by a 1:10 dilution -how would you do this? Again, make 1 Liter. 3. Suppose you wanted a 2: 50 dilution of a stock solution, but you wanted 200 mL of it. How would you make this? . What if you only wanted 10 mL of the 2:50 dilution - how would you make this solution? Use the following data to prepare a standard curve. Attach the curve to this assignment. Absorbance Concentration of the standard solutions in ug/mL 0.32 1.0 μgmL 0.56 2.0 μg/mL 0.79 3.0 μg/mL. 1.33 5.0 μg/mL 1.50 6.0 μgmL 1.77 7.0 μgmL

Answer 1

Ans 1. To make a 4M NaCl solution, 1L

As we know to calculate the molarity, formulae is number of moles divides by volume of solution is Litre.

Now, to calculate number of moles, formulae is weight of NaCl divided by molar mass of NaCl.

To calculate how much amount of NaCl ( x grams) should we weigh for making 4 M. Use the above Formula. Calculate no. Of moles

No. Of moles = x/58.44

Molarity= x/58.44 X 1

------> 4 = x/ 58.44 X 1

x = 233.76 g of NaCl needs to be weighed.

Now, take a 2L beaker and add 233.76 g of weighed NaCl.

Add 500 mL water in it and keep it on magneitc stirrer to dissolve it completely.

Once salt is dissolved, make up the volume to 1 L using water.

Ans 2. To dilute this 4 M NaCl solution to 1:10, measure 100 mL of 4 M NaCl using measyring cylinder and make the volume of it to 1 L using water by adding 900 mL water.

When we will take the ratio of 100: 1000 that is 100 mL 4 M NaCl in 1 L solution, it will be 1:10.

Ans 3. To make 2:50 dilution of stock solution, 200 mL.

To calculate how much amount of stock solution is required = 2/50 multiplied with 200 (because we want final volume to be 200 mL) = 8.

So, measure 8 mL of 4 M NaCl (stock solution) using measuring cylinder and make up the volume to 200 mL by adding 192 mL water. This will make the dilution to 2:50.