help with these chem pre lab questions ! thank you :) just 1-3 is needed. I need
ID: 914470 • Letter: H
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help with these chem pre lab questions ! thank you :) just 1-3 is needed. I need the results for 4-5 yet.
What do you expect the signs of the molar heats of fusion and vaporization to be? What about the signs of the entropy changes associated with fusion and vaporization? Keeping in mind that entropy can be viewed as a measure of disorder (the higher the entropy the greater the disorder), would you, for a given substance, expect greater entropy changes to be associated with fusion or with vaporization? Explain your answer For Part II. the temperature vs. time plots will not be linear over the entire temperature range. The rate of temperature increase actually slows as the temperature of the water increases How can you explain this? Re-read the instructions for the first two parts of the 'Results' section in Part II. If, from the temperature vs. time plot for water, a heating rate of 0.233 degree C/s is calculated, how many Joules per second are being supplied to the water by the bunsen burner? The mass of water in the can is 163.2 g. Following up on question 4, it was found that 10 min. of boiling evaporated 43.8 g of water What is the molar heat of vaporization of water?Explanation / Answer
1) Both molar heat value will have positive sign as heat is used up in change of state from solid to liquid (fusion) and for liquid to vapours(vaporisation).both are endothermic reactions.
Positive entropy changes for both fusion and vapourisation.
2)Entropy changes is the measure of disorderliness.In change of state from solid to liquid (fusion) disorderliness increases as molecules are more scattered in liquid ,but in solid they are fixed in their position.Entropy change is positive.
Similarly, for change of state from liquid to vapours(vaporisation),disorderliness of molecules further increases as in gases they are far apart and free with respect to each other compared to liquid.Entropy change is positive.
3)As the temperature of water increases,a smaller and smaller percentage of heat added goes towards increasing the temperature, and rest of the heat is used up in change of state from solid to liquid (fusion) and for liquid to vapours(vaporisation).both are endothermic reactions.
Afetr boiling point is reached, all the heat is used up in change of state.no increase in temperature takes place until total change of state from liquid to vapor takes place at b.pt.The temperature remains constant (=boiling point) for the time being.
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