Question

Please answer all parts if possible:

Describe how to prepare a 20.00 µg/mL iron solution from a 1 000 mg/mL iron standard solution using 10-mL and 50-mL volumetric pipets and 500-mL and 1 000-mL volumetric flasks.

Accounting for buoyancy, what APPARENT mass of CsCl (density = 3.988 g/mL) in air should you weigh out to obtain a TRUE mass of 1.267g?

Part B:

By using the ideal (perfect) gas law (PV = nRT), calculate the density of He at 20 ^oC and 1 bar.

Find the true mass of Na (density = 0.97 g/mL) weighed in a glove box with a He atmosphere, if the apparent mass is 0.823g.

Answer 1

1) Prepare 500 mL of the diluted solution, calculate the volume of concentrated solution needed:

V1 = C2 * V2 / C1 = 20 ug / mL * 500 mL / 1000 ug / mL = 10 mL

Measure 10 mL of the concentrated solution and deposit in a 500 mL flask, complete with distilled water.

2) He density is calculated, from the ideal gas equation:

d = P * MM / R * T = 1 atm * 4 g / mol / 0.082 atm * L / mol * K * 293 K = 0.166 g / L

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