Article: Scientists frequently use a set of temperature and pressure values as a sort of convenient "default". These values are called Standard Temperature and Pressure (or STP for short). Vapor pressure problems frequently make reference to STP conditions, so it's handy to have these values memorized. STP values are defined as: Temperature: 273.15 K / 0 C / 32 F Pressure: 760 mm Hg / 1 atm / 101.325 kilopascals In our example in Section 1, we saw that the Clausius-Clapeyron equation is very useful for finding the vapor pressures of pure substances. However, not every question will ask you to find P1 or P2 many will ask you to find a temperature value or even sometimes an Hvap value. Luckily, in these cases, getting the right answer is simply a matter of rearranging the equation so that the variable you're solving for is alone on one side of the equals sign. For instance, let's say that we have an unknown liquid with a vapor pressure of 25 torr at 273 K and 150 torr at 325 K and we want to find this liquid's enthalpy of vaporization (Hvap). We could solve like this: ln(P1/P2) = (Hvap/R)((1/T2) - (1/T1)) (ln(P1/P2))/((1/T2) - (1/T1)) = (Hvap/R) R (ln(P1/P2))/((1/T2) - (1/T1)) = Hvap Now, we plug in our values: 8.314 J/(K Mol) (-1.79)/(-0.00059) = Hvap 8.314 J/(K Mol) 3,033.90 = Hvap = 25,223.83 J/mol In our Raoult's Law example above, our solute, sugar, doesn't produce any vapor on its own at normal temperatures (think when was the last time you saw a bowl of sugar evaporate on your counter top?) However, when your solute does evaporate, this will affect your vapor pressure. We account for this by using a modified version of the Raoult's Law equation: Psolution = (PcomponentXcomponent) The sigma () symbol means that we just need to add up all of the different components' vapor pressures to find our answers. For example, let's say that we have a solution made from two chemicals: benzene and toluene. The total volume of the solution is 120 milliliters (mL); 60 mL of benzene and 60 of toluene. The temperature of the solution is 25 C and the vapor pressures of each of these chemicals at 25 C is 95.1 mm Hg for benzene 28.4 mm Hg for toluene. Given these values, find the vapor pressure of the solution. We can do this as follows, using standard density, molar mass, and vapor pressure values for our two chemicals: Mass (benzene): 60 mL = .060 L &times 876.50 kg/1,000 L = 0.053 kg = 53 g Mass (toluene): .060 L &times 866.90 kg/1,000 L = 0.052 kg = 52 g Moles (benzene): 53 g 1 mol/78.11 g = 0.679 mol Moles (toluene): 52 g 1 mol/92.14 g = 0.564 mol Total moles: 0.679 + 0.564 = 1.243 Mole fraction (benzene): 0.679/1.243 = 0.546 Mole fraction (toluene): 0.564/1.243 = 0.454 Solve: Psolution = PbenzeneXbenzene + PtolueneXtoluene Psolution = (95.1 mm Hg)(0.546) + (28.4 mm Hg)(0.454) Psolution = 51.92 mm Hg + 12.89 mm Hg = 64.81 mm Hg
Question: What is a summary of what this article is about?
Be aware of Standard Temperature and Pressure conditions. Rearrange the Clausius-Clapeyron equation to find other variables. Account for the vapor pressure of the solute when it produces vapor.
Article: In order to be able to measure the circumference of your leg, you need a measuring tape that it not stiff. The easiest tapes to use are those made for measuring for sewing, as they are made to measure parts of the body. Flexible measuring tapes are available at most craft, sewing, and big box stores. In order to get a perfect measurement, it's important to have another person to help you. If you have one, your physiotherapist is an ideal person to help. This will allow you to position your leg correctly while they do the actual measuring. This process can be done on your own if absolutely necessary. However, it is much easier to have an assistant. To measure correctly for a knee brace, you should be in your normal standing position. This allows the knee and leg to be easily measured and it gives an accurate reading. When standing, your leg is not normally totally straight. Your knee should have a small bend that is about 30 degrees. If you have an injury that doesn't allow you to put pressure on your leg, simply extend it as much as you can. Then take your measurements without the foot touching the ground. Sitting can also be an option if you can't find someone to assist you. Stretch your legs out straight in front of you as best as you can.
Question: What is a summary of what this article is about?
Get a soft, flexible measuring tape. Find someone to help you. Stand up. Sit to take measurements if standing is too painful.
Article: Choose something that is easy to remember but also stands out from the crowd like, "Beauty and the Geek Productions" or "Lovable Varmint Productions". Search around on the internet to make sure you aren't infringing on copyright laws. Yes, even movie production companies have a trademark or copyright on their name to secure it so that no one else will use it. The profile should include the following important elements: Name of your company, its establishment (year), founder(s) of the company, vision, mission and the goal of the company, where do the company works, the kind of activities the company carries out and the structure of the company. Also clarify the company's partners (such as broadcasters, institutes, co-production partners) and the contacts of the company (this is very important because it will enable your clients get in contact with you easily, especially for business purposes).
Question: What is a summary of what this article is about?
Come up with a name for your production company. Create your production company profile.