In: Chemistry
#6...
4. How would you make 500 ml of 5 M NaCl?
5. How would you make 1 liter of 2 M sodium citrate?
6. How would you make 1 liter of stock 20X SSC (standard sodium citrate) buffer that is 3 M NaCl, 0.3 M sodium citrate, using the solutions you made in Q4 and Q5 above?
4.How would you make 500 ml of 5 M NaCl?
Answer: Molarity = (weight of Solute/Mol.weight) (1/volume in L)
5M = (weight of NaCl/ 58.44 g/mol )(1/0.5L)
Weight of NaCL required = 5 M x 0.5 L x58.44 = 146.1 g
Therefore, we need to weigh 146.1 g of NaCl and dissolve into 500 mL solution to make our required solution(500mL of 5M NaCl).
5. How would you make 1 liter of 2 M sodium citrate?
Answer : Molarity = (weight of Solute/Mol.weight) (1/volume in L)
2 M = (weight of Sodium Citrate)/ 258
Weight of Sodium Citrate= 516 g
Therefore, we need to weigh 516 g of sodium citrate and dissolve it into 1 L water. This will give us the 1L of 2M sodium citrate solution.
6. How would you make 1 liter of stock 20X SSC (standard sodium citrate) buffer that is 3 M NaCl, 0.3 M sodium citrate, using the solutions you made in Q4 and Q5 above?
20X SSC solution contains 3M NaCl and 0.3 M sodium citrate.
We need to find out how much volume of 2M sodium citrate and 5M of NaCl is required.
Let us find out for NaCl:
Initial volume V1 =?
Initial concentration M1 = 5M
Final Volume V2 = 1L
Final Concentration M2 = 3M
M1V1 = M2V2
V1= M2V2/M1 = 3M x 1L /5M = 0.6 L
For sodium citrate:
Initial volume V1 =?
Initial concentration M1 = 2M
Final Volume V2 = 1L
Final Concentration M2 = 0.3M
M1V1 = M2V2
V1= M2V2/M1 = 0.3M x 1L /2M = 0.15 L
Therefore, we need to mix 600mL of 5M NaCl and 150 mL of sodium citrate solution and make up the final volume to 1L(i.e, 250 mL of water).