Experiment 8 Pre-Lab Questions Answer all calculation questions to the correct n

Question

Experiment 8 Pre-Lab Questions Answer all calculation questions to the correct number of significant figures. I. What pressure in atmospheres corresponds to 720.3 mm Hg? 2. What temperature in K corresponds to 97 °C 3. A student performs the experiment and records the following data: . Barometric pressure: 741.6 torr Temperature of water bath: 99 °C . Volume of flask: 273 mL . Mass of condensed vapor: 0.65 g a. The student calculates the molar mass of the gas to be 2.6 × 10-5. What mistake did he make? b. What is the molar mass of the gas? Show your calculations. Why it is not necessary to measure the volume of the unknown liquid that is placed in the flask? 4. 5. Refer to the equation that relates to the mass of the vapor (w). If either w or T is somehow too large or if either P or V is too small, then Mwill be too large. Give an example of a procedural error that would result in obtaining a molar mass value larger than the true value.

Explanation / Answer

Question-1

1 mm Hg = 1/760 atm

therefore 720.3 mm Hg = 720.3 x (1/760 atm)

= 720.3 / 760 = 0.9477 atm.

Question-2

1 0 C = 273 Kelvin

To convert from celcius to kelvin add 273 with the temperatue in 0C. So 970C = 97 +273 = 370 K

Question -3

Pressure, P = 741.6 torr

Volume, V = 273 mL

R = 8.314 J/molK

T =990 C

Number of moles = given mass/ molar mass

Molar mass = Given mass/ number of moles

Ideal gas equation, PV = nRT, where n= M/m

PV = (M/m) RT

where M = given mass and m = molar mass

m = (M x R x T ) / P V

= (0.65 gx 8.314 x 990C ) / (741.6 x 273 mL)

=2.64x10-3

But the answer showing 2.64x10-5, means he divided some quantity with 100.

Question-4

The ideal gas equation connected with the properties of gas formed from the liquid present in flask. So Ideal gas equation cannot correlate with liquids.

Question-5

Pressure as well as volume are inversely proportional to Molar mass (from ideal gas). So if the molar mass become large from the real value means pressure or volume may be mistaken or increases from its real value instead of decreasing.

Question-6

Don’t Smell directly, because toxic gases may be present in the compound like Chloride or cyanide, or else bad or pungent smell will irritate you. So smell by waving, that is cup your hand above the test tube or container and waft the air toward your face.

Question-7

The acidic substances will change blue colour litmus paper into red and basic substances will convert red litmus to blue colour. But neutral substances will not make any change to litmus paper.

So the first amswer is Acid and Second is neutral.

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