Anonymous

# which of the following actions would be likely to change the boiling point of a sample of pure liquid in an?

open container?

i. placing it in a samler container

ii. increasing the number of moles of liquid in the container

iii. moving the continaer and liquid to a higher altitude

A. i only

B. ii only

C iii onlyu

D. Ii and iii only

E. i, ii, and iii

Relevance

The rate of change of the boiling point temperature is given by the following equation: dTb/dP = (TbDVvap,m)/(DHvap,m). d mean delta or change D is also delta or change. Tb is the absolute boiling temperature in Kelvin. P = Pressure. Hvap,m= Molar Enthalpy (heat) Of Vaporation. Vvap,m = Molar Volume change on vaporation.

What does this mean? It means that the things that impact boiling point, Tb, are Temperature, pressure, and volume. So, we know that decreasing volume in a closed system will increase pressure, i. We know that increasing the number of molecules in the same volume in a closed system will increase pressure, ii. Both of these will increase the boiling point. But, in and open system (container) there is no net change. Moving to a higher altitude decreases pressure. In a closed system what occurs outside would not impact what is going on inside, but in an open system the outside pressure will impact the contents. This will actually decrease the boiling point, iii. So, the answer, assuming an open system, is C, iii only.

I hope this helps. Please study hard.

• Som™
Lv 6

C iii only

Boiling Point Variation :

The standard boiling point for water at 100 oC is for standard atmospheric pressure, 760 mmHg. It is the experience of high altitude hikers that it takes longer to cook food at altitude because the boiling point of water is lower. On the other hand, food cooks more quickly in a pressure cooker because the boiling point is elevated. Raising or lowering the pressure by about 28 mmHg will change the boiling point by 1 oC. Although the vapor pressure variation with temperature is a non-linear one, the boiling point variation can be approximated near 100 oC by an empirical fit of the available data. This can provide the following estimate of the boiling point: For a pressure of 1mmHg, the boiling point will be approximately 1oC. For variations in atmospheric pressure with altitude according to the barometric formula, the boiling point at a height of m = ft above sea level (atmos. pressure mmHg) would be approximately1 oC.