231. Demonstration: Sublimation: Examples of solids that can sublime at room temperature: 1) Solid iodine, I2 (s) 2) Dry ice or solid carbon dioxide CO2 (s) 3) Any ammonium compound as ammonium chloride, NH4Cl and ammonium bromide, NH4Br232. Demonstration: Simple Distillation233. Demonstration: Fractional distillation. Discuss briefly: fractional distillation of liquefied air and fractional distillation of crude oil.234. Demonstration: Separating funnel235. Adsorption: means sticking to the surface.236. Adsorption: sticking of the particles of one material on the surface of another. Examples of adsorbing substances: Silica gel: adsorbs water vapor, Charcoal: adsorbs gases with strong odor and removes colored impurities from a solution237. Demonstration: Chromatography. It is the technique used to separate different compounds, especially those that can be easily destroyed by heat or chemicals. It can be used to separate colored components as: 1) Green liquid obtained by squashing green leaves. 2) Black ink. The property that carries the liquid up the paper is capillary action.238. Demonstration: Crystallization239. Alcohol is flammable, therefore it cannot be heated directly. To heat alcohol, we should use a steam bath or an electric heater.240. If you need to collect sugar from sugar alcohol solution heat the solution using an electric heater to crystallization point. Leave the solution to cool and crystals to form. Filter off the crystals.241. Vapor pressure and temperature are proportional NOT directly proportional. At the same temperature, the vapor pressure is the SAME. For the same liquid, the only factor affecting the pressure of the liquid is the temperature.242. Minimum conditions for liquid molecules to vaporize: 1) Molecules are supposed to be on the surface. 2) Molecules are supposed to have an average kinetic energy greater than the energy keeping the molecules in the liquid state.243. Water has a vapor pressure of 17.5 mmHg at 20oC. Which of the following will increase the vapor pressure of water? a) Transferring water to a larger container. b) Cooling water to 10oC c) Taking the container to the top of the mountain. d) Heating the water to 32oC244. Boiling point: is the temperature at which the liquid vaporizes anywhere in the solution.245. At the boiling point: a. Vapor pressure is equal to the surrounding pressure. b. Bubbles of vapor can form anywhere within the liquid. c. Molecules escape from the surface of the liquid to enter the gas phase as vapor (this also happens at room temperature). d. With increasing altitude, atmospheric pressure decreases and so does boiling point.246. Normal boiling point: is the temperature at which the vapor pressure is exactly 1 atm or 760 mmHg.247. Molar heat of fusion: is the energy required to change one mole of a substance from solid to liquid at the same temperature and constant pressure.248. General equation for Molar heat of vaporization: X (l) + heat ⇌ X (g)249. General equation for Molar heat of condensation: X (g) ⇌ X (l) + heat250. In general, a substance that has a higher boiling point is expected to have a
Here are the points from 251 to 260:251. An aqueous solution is one in which the solvent is water.252. Salt and water is an example of aqueous solutions where the solute is a solid.253. Alcohol and water is an example of aqueous solutions where the solute is a liquid.254. Ammonia and water is an example of aqueous solutions where the solute is a gas.255. Concentration: relative amounts of solute and solvent.256. Molar concentration (Molarity): is the number of moles of solute per liter (dm3) of solution. (the relative amounts of solute and solution)257. Concentration of a given solution does not change if solution is split into fractions.258. Relationships between n, V, C and m, M, V, C: n = CV, 𝐂 = 𝐦/𝐕, 𝐕 = 𝐦/𝐂, m = n × M, m = CVM, 𝐌 = 𝐦/𝐂𝐕259. Preparing solutions with given concentrations.260. A 2 L bottle of 0.35 M solution is split into ten containers of 100ml capacity. What is the concentration of the solution in each of the new containers? a) 0.75 M b) 0.0035 M c) 2.0 M d) 0.35 M e) 100 M