Dilution problems. 10) Prepare 100 ml of a 0.5M NaOH solution. MW of NaOH is 40.

Question

Dilution problems.

10) Prepare 100 ml of a 0.5M NaOH solution. MW of NaOH is 40.0 11) Prepare 500 ml of a 2.0M NaCI/0.SM NaOH solution. MW of NaCl is 58 12) Prepare 100 ml of a 10% SDS solution. Mw of SDS is 288.4 13) Using the following stock solutions, 1.0M Tris-HCI, 1.0M NaCl, 0.5M EDTA, prepare 500 ml of a 0.2M Tris-HCI/0.4M NaCl/0.1M EDTA solution. 14) From a stock solution of 3.3 mg/ml stock of DNA, make a 250 ul solution of 1.5 ng/ul DNA. 15) A solution contains 2.5 x 108 bacteria/ml. An aliquot of 10 ul is diluted into 10 ml to give solution A. 500 ul of solution A is diluted into 10 ml to give solution B. 1 ml of sol ution B is spread on a plate. How many colonies are expected given that a colony arises from one bacterial cell.

Explanation / Answer

10)

volume , V = 100 mL

= 0.1 L

use:

number of mol,

n = Molarity * Volume

= 0.5*0.1

= 5*10^-2 mol

use:

mass,

m = number of mol * molar mass

= 5*10^-2*40

= 2 g

Take 2 g of NaOH and add enough water till final volume becomes 100 mL

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