Question

Hi please help me answer these questions!

Is the formation of bubbles in a liquid a necessary condition and a clear indication that a liquid has reached its boiling point? 5. H. How many boiling points does water have? If more than one, what determines what each of these points will be? 6 Solid carbon dioxide, commonly known as "dry ice", is seen at room temperature to spontaneously convert to vapor through sublimation. (a). Why is it that no one speaks of wet "dry ice" (i.e. you never think of seeing dry ice melt into a liquid before it evaporates)? (b). What is the normal boiling point of CO2? - What is the name given the set of conditions where a substance can freeze and boil at the same time?

Answer 1

4. The formation of bubbles is not a necessary condition that a liquid has reached its boiling point, because the bubble can form even before boiling. We can see bubbles on the sides or the bottom of the apparatus that we use for boiling water when it is hot. Formation of bubbles just implies that the apparatus is warm and is transferring energy to the liquid.

Boiling point is the temperature at which the vapour pressure of the liquid reaches the pressure outside the system.

5. As mentioned above, the boiling point is the temperature at which the vapour pressure of the liquid reaches the pressure outside the system ( atmospheric pressure). So the boiling point is dependent on the pressure on the system.

At normal temperature and pressure ( 25 degree Celsius and 1atm pressure) boiling point of water is 100 degree Celsius. At higher pressure higher boiling point and at lower pressure lower boiling point are obtained.

The relationship can be seen from

PV = nRT

P $\alpha$ T

6. (a) It is because we normally see dry ice at our room temperature which is beyond the melting point and boiling point of carbon dioxide( boiling point= -78.46 degree Celsius and melting point of carbon dioxide = -56.6 degree Celsius). The room temperature is 25 degree Celsius. So that the dry ice is directly converted into gas without passing into the liquid state. This can be explained by using the phase diagram of carbon dioxide which is given as the picture below

B Curve pressure (not to scale ) Melting Liquid solid 5. latmt - - Vaporization curve latm gas A sublimati cuore -78.46 - 56.7 Temperature (°C) csarned with CamScanner

(b) normal boiling point of carbon dioxide is -78.46 degree Celsius.

7. The point at which the substance can boil and freeze at the same time is called the "Tripple Point". From the above picture you can see that at the point O all the states coexist in that point. For CO2 the tripple point exist at 5.1atm pressure and at -56.7 degree Celsius temperature.