propanone Table 1.1 - Potential unknowns and their formula CH,0 iew your procedu
ID: 567482 • Letter: P
Question
propanone Table 1.1 - Potential unknowns and their formula CH,0 iew your procedures and identify as many potential sources for error as pesso a. Determine if your errors are systematic or random. b. How would each error change your calculated value for molar mass (i.e. Would the error increase or decrease your calculated value?). ALLAAAAAAA Use your textbook or other sources and find any constants or conversion factors you might need to evaluate for the molar mass. Assume that the pressure could be given in any one of the following units: inHg, cmHg, mmHg, torr, atm, or bar. A flask with a total volume of 289.33 ml was found to contain 0.3546 g of vapor at 99.88°C on a day when the barometric pressure was 29.00 inHg. What was the molar mass of the unknown?Explanation / Answer
Molar mass determination of volatile liquid:
To determine the molar mass (M)of a volatile liquid,the liquid is evaporated in a flask of measured volume(V) being submerged in boiling water,so that the temperature(T) of water equals that of gas in the flask.After the liquid condenses,the mass of the flask+liquid is measured and substracted from the mass of flask to calculate the mass of liquid(m).Barometric pressure (P)is also noted and all the values plugged in the ideal gas equation,PV=nRT=m/M RT
or,PV=(RTm/M)
potential sources oferror include:
b) 1) error in mass measurements of flask,condensed liquid,mass of water.Mass of flask must be measured by filling it with water(mass of flask+water) and after removing the water and drying it completely for mass of flask, else the measured value of volume will be less.This will give high molar mass value.
2)Measured exact temperature of boiling water(temperature must be measured quickly as the liquid vaporises or it may be reported low).Low temperature gives low M value.
3) measured barometric pressure of laboratory..Low P gives high M
4) limited heating time of the liquid in the flask as longer heating may let the vapor escape to a greater amount from the set pinhole ,decreasing the mass of condensed liquid ,giving lower M
You put more than enough ;liquid in the flask and a pinhole is bored in the flask for excess vapor to escape,so that only sufficient vapor that fill the flask remains.But ,the escaping vapor may fluctuate and thus the barometric pressure may be increased.This decreases the value of Molar mass as per the equation
a) systematic error come from error in the measuring instruments- error 1) mass measurement errors
random errors arises due to errors in experimental methods-rest errors listed above
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