Help with Concentration problems plz

[Kobebucsfan]

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1) If you dissolve 9 mg glucose in 5 mL of water, what is the concentration of glucose in mM and microM ??



2) How many millimoles and micromoles of glucose are present in 9 mg glucose ?

 

[Toothiemctooth]

C6h12O6
72+12+96

180 g/mol

9g/180g = 0.05 moles

M = n/Vl =
0.05 (mol)/0.05 (l) = 1 M

1 M = 1000 mM

1 M = 1 x 10^6 macroM

That's what I got. Tell me if that's correct.

 

[ekephant]

1) This question requires knowing the molecular formula for glucose: C6H12O6.
From that you can calculate the molar mass: ~180 g/mol.
Now with the molar mass you can convert the 9 mg into mols: 9mg(1g/1000mg)(mol/180g) = 1/20,000 = 0.00005 or 5x10^-5 mol.
Convert the 5 mL into L: 5mL(L/1000mL) = 0.005 L.
Use this information to calculate the concentration in M, then mM and µM: 0.00005 mol/0.005 L = 0.01 M = 1x10^-2 M = 1x10^-5 mM = 1x10^-8 µM

2) Again use the molecular formula and molar mass to convert 9mg of into mols. From the above question we know that 9mg of glucose is equivalent to 5x10^-5 mol of glucose. Then simply convert to mmol and µmol: 5x10^-5 mol = 5x10^-8 mmol = 5x10^-11 µmol