# Homework Exams

A place for HW Exam tips, hints, and errata.

## Chapter 10

• Q4 – A line is drawn through a set of data points and the equation for this line is given on the plot. This is related to the Clausius-Clapeyron equation linear form.
• Q5 – You can also find appropriate values for water here. Remember, depending on the values you choose, your final answer can be different from the posted answer.
• Q9 – For IMFs and KE columns, you will report “Increasing” or “Decreasing”.
• Q11 – You can also find appropriate values for water here. Remember, depending on the values you choose, your final answer can be different from the posted answer.
• Q13 – For points a and e, consider the horizontal dashed line drawn through these points.

## Chapter 11

• Q3 – Raoult’s Law
• Q4 – Assume
• Q6 – Assume
• Q7 – 4.10 × 10–2 ppm counts as a correct answer
• Q8 – Raoult’s Law
• Q9 – Boiling point elevation
• Q10 – Osmotic pressure
• Q11 – Freezing point depression
• Q12 – Assume; Boiling point elevation
• Q13 – Try to do the math quickly in your head (no calculator; no pencil/paper)
• Q15 – Boiling point elevation
• Q16 – I asked everyone to read up on this one (do you remember?)
• Q18 – Osmotic pressure

## Chapter 12

• Q10 – Change H2OH (product in step 1) to H2O. Everything should then already be balanced.
• Q13 – Hint: Consider critically the following phrase in the question… “when the rate has been tripled.”

## Common HW Exam Issues

For HW Exam 10, the following were some common issues.

### Units

Assign all non-dimensionless numbers units in all of your work.

### Show all work

Be sure to show all work. For example, when manipulating numbers, explicitly show the conversions (with units) being made to transform the number.

### Do not “invent” numbers

Some of you based some math work off of “invented numbers”. This is not good and should never be counted as complete for any reason. Rather, simply cross out the work (or don’t write anything) and mark the question as Incomplete.

Inventing a number out of thin air to “show work” that “results in” the right answer is not acceptable.

### Cover page total

Be sure to write the total points (round all fractions up) on the total line of the self-evaluation sheet. Be accurate when totaling the points.

Many missed Question 6 when it asked to “Identify all phase transitions…”. Be sure to read the question carefully and include all relevant information that the question is asking for.

### Self-Evaluation

Use the self-evaluation time to critical analyze your work. Think thoughtfully as to whether or not the work that is provided meets the following:

1. Units on all numbers (where appropriate). Don’t include units on dimensionless numbers. That would be inappropriate.
2. Show ALL work
3. Answer all component(s) of a question
4. Demonstrate some modicum of knowledge about the question and a logical response.

Really take the time to evaluate your work before turning it in. This is your chance to submit an evaluation that accurately reflects your work! It is better to mark a question as Incomplete than to risk getting a zero for the entire assignment!

### Organization

Many of you did some spectacular work that was a pleasure to evaluate. This work was easy to follow and very well organized. Some of us put little effort into the layout and presentation of the work. Take some pride in the work being performed and keep things neat. An organized and structured approach aids in learning and makes it easy to go back and review when studying. It also makes it easier for the evaluator!

### Ensure a quality PDF document

A few people submitted work where some pages were blurry beyond recognition. Please be sure that each page is readable. If not, recapture the work in a new PDF.

### Ensure your work is legible

If I cannot read your work, I cannot evaluate it and it will not receive credit. Take the time to make it legible!

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