Determine the concentration of the following using the solutions Molarity a. Her

Question

Determine the concentration of the following using the solutions Molarity a. Here are the formula weights for three compounds often used in molecular biology: NaCl, 58.44 g/mol Tris Base, 121.11 g/mol EDTA, 372.2 g/mol For each of these three compounds, how much solute is required to make 0.75 L of a 1M solution?

B. How much solute is required to make 750 mL of a 0.2 M solution of Tris Buffer. FW of Tris= 121.1g

C. How would you make 75 mL of a 2.5M solution of sodium hydroxide, NaOh?

D. How would you prepare the following solution? 175 mL of 55mM Nacl (FW 58.8 g)

Explanation / Answer

A) 0.75 L of 1 M NaCl:

Moles of NaCl = concentration*volume = 0.75*1 = 0.75 mol

Mass of NaCl required = molar mass*number of moles = 58.44*0.75 = 43.83 g

0.75 L of 1 M tris base:

Moles of tris base = concentration*volume = 0.75*1 = 0.75 mol

Mass of tris base required = molar mass*number of moles = 121.11*0.75 = 90.83 g

0.75 L of 1 M EDTA:

Moles of EDTA = concentration*volume = 0.75*1 = 0.75 mol

Mass of EDTA required = molar mass*number of moles = 372.2*0.75 = 279.15 g

B) Concentration = 0.2 M

volume = 750 ml = 0.750 L

Moles of tris buffer = concentration*volume = 0.2*0.750 = 0.150 mol

mass of tris base required = 121.1*0.150 = 18.165 g

C) Concentration = 2.5 M

volume = 75 ml = 0.075 L

Moles of NaOH = concentration*volume = 2.5*0.075 = 0.1875 mol

mass of NaOH required = 40*0.1875 = 7.50 g

Add 7.50 g of NaOH to 75 ml of water.

D) Concentration = 55 mM = 0.055 M

volume = 175 ml = 0.175 L

Moles of NaCl = concentration*volume = 0.055*0.175 = 0.0096 mol

mass of NaCl required = 58.8*0.0096 = 0.564 g

Add 0.564 g of NaCl to 175 ml of water.

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