2. Need 500 mL of 0.2 M Tris-HCI, pH 8.0 2 groups prepare this a. What is the fo

Question

2. Need 500 mL of 0.2 M Tris-HCI, pH 8.0 2 groups prepare this a. What is the formula weight of Tris-HCI? (1) b. How many grams of Tris-HCl do you need? (3) c. How many ml of water will you dissolve the Tris-HCI in? (1) d. What is the expected pH of the original solution? (3) e. Will you need to add HCI or NaoH to the original solution to adjust the pH to 8.0? (1) f. How much HClNaoH do you expect to need to add? What concentration of HCVNaoH? (5) g. How much HCVNaOH did you actually add to achieve pH 8.0 (1)

Explanation / Answer

a.

Chemical Names: Tris hydrochloride; Tromethamine hydrochloride

Formula:           C4H12ClNO3

Formula Weight:

(4x 12 + 12 x1 + 35.5 + 14 + 3 x 16 )= 157.5 g /mole

b.

Tris (acid form) molecular weight = 121.1g/mole

Gram of Tris HCl needed for making 500ml of 0.2 M tris HCl

= 0.500L x 0.2mol/L x 121.1g/mol

= 12.11g

c.

ml of water is needed to make 500ml of 0.2 M Tris HCl

Moles of Tris = mol/L x L

= (0.2 /1000) x 500 = 0.1M

Grams of Tris =12.11g

Dissolve the Tris into distilled deionized water, 1/3 of 500ml volume .Mix in1M HCl until the pH meter gives the desired pH for Tris buffer solution. Add the Tris HCl mixture to a volumetric flask of the desired volume and add deionized water as required to complete the solution.

d Expected pH range of original solution is 7.0 to 9.0.

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