Describe the process you would use to prepare 350 mL of a solution containing 0.
ID: 474908 • Letter: D
Question
Describe the process you would use to prepare 350 mL of a solution containing 0.25 M sucrose and, 4 M methanol. Sucrose has a molar mass of 342.3 g/mol. Methanol has a molar mass of 32.04 g/mol and a density of 0.7918 g/mL. You are following a protocol that requires at least 333 ml of a 250 mM of HEPES solution. You search the lab and can only find a 2 M HEPES solution. Describe how you would dilute the stock to achieve your needs. HEPES has a molar mass of 238.30 g/mol. Suppose you decide you don't trust your lab mate's stock solution and want to make up the 250 mM HEPES solution fresh. Describe this process. HEPES has a molar mass of 238.30 g/mol.Explanation / Answer
350 ml of sucrose 0.25 M
Molarity = moles X molecular weight
= 0.25 X 342.3 = 85.575 g/L
But we need 350 ml of 0.25 M solution = (85.575/1000) X 350 = 29.95 grams of sucrose dissolved in
100 ml water and make up to 350 ml
350 ml of 4 M methanol
Molarity = moles X molecular weight
= 4 X 32.04 = 128.16 g/L
Volume = mass/ density = 128.16/ 0.7918 =161.86 ml/L
But we need 350 ml of 0.25 M solution = (161.86/1000) X 350 = 56.65 ml of methanol dissolved in
100 ml water and make up to 350 ml
To prepare 333 ml of 0.25 M(250mM) HEPS
(MV)given = (MV)required
Vgiven = (MV) required/ Mgiven = (0.25 X 333)/2 = 41.625 ml
Add 41.625 ml of 2 M HEPS solution and dilute it to 333 ml
To prepare 333 ml of 0.25 M(250mM) HEPS freshely
Molarity = moles X molecular weight
= 0.25 X 283.3 = 70.825 g/L
But we need 333 ml of 0.25 M solution = (70.825 /1000) X 333 = 23.58 g of HEPS dissolved in 100 ml
solvent and make up to 333 ml
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