prelim_pract2 - Practice problems for Prelim 2 Fall 2007 1...

Info icon This preview shows pages 1–4. Sign up to view the full content.

Practice problems for Prelim 2, Fall 2007 1. You are working in a lab and you see a sealed 1 liter flask sitting on the lab bench. There is some liquid in the bottom of the flask. You recall that you boiled some liquid in that flask, driving off all air in the vapor space above the liquid. Then, you sealed the flask tight and let it cool to the lab temperature (30°C). However, you cannot recall whether it was ethanol or ethyl acetate that you boiled, and you forgot to label the flask (which is a serious violation of EPA rules!) Fortunately, the flask is fitted with a pressure gauge that reads 120 mm Hg. a) Write down a calculation that shows whether the material in the flask is ethanol or ethyl acetate. Explain your reasoning and state assumptions. b) You estimate there is 10 ml of liquid in the flask. What is the total mass in the flask?
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

2. A drier must remove 200 kg H 2 O per hour from a certain material. Air at 22°C and 50% relative humidity enters the drier and leaves at 72°C and 80% relative humidity.
Image of page 2
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.