These relative weights computed from the chemical equation are sometimes called equation weights. The formula weight is simply the weight in atomic mass units of all the atoms in a given formula. Upper Saddle River: Prentice Hall College Div, 2005. A random error can be solved by repetition of the experiment. Collect several hundred cubic centimeters or mL of gas. The more trials completed, the closer the average molar mass of butane is to the accepted value of the molar mass of butane. An Alkane is when the compound is formed by single bonds connecting the carbons and hydrogens.
When calculating molecular weight of a chemical compound, it tells us how many grams are in one mole of that substance. There are 4 carbon atoms per molecule. The percentage by weight of any atom or group of atoms in a compound can be computed by dividing the total weight of the atom or group of atoms in the formula by the formula weight and multiplying by 100. A possible systematic error that may have occurred in this lab is that the butane from the lighter may have contained air or a substance other than butane in the lighter, skewing the measured amount of butane gas collected at the top of the beaker. Repetition does not solve systematic errors, and the value is referred to as a bias or the deviation from the true value.
By choosing the value of the subscript of carbon to be exactly 4, all of the experimental error shows up in the subscript for hydrogen. Walter Snellings in Pittsburg and he gas is used for cigarette lighters, heaters, stove fuels, and other heating appliances. Time Teacher preparation: 30 minutes Presentation: 30 minutes Several drying steps Class Time: 45 minutes Hazards Butane is flammable. This is shown as a lecture experiment, but can be performed as a student experiment when balances of adequate sensitivity 0. Then we recorded the final volume of water, and repeated the experiment until we had three trials. There are 4 carbon atoms per molecule.
Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your with the - enabled for use with the amazing, fun and free and. The lighter is weighed both before and after the gas is withdrawn. The molecular weight of a pure compound is determined from its chemical formula and the atomic weights of its elements. Determine percentage error for your data. A systematic error is an error caused by a variation in samples. The measurements in the lab are reliable taking into consideration the equipment windows of error and there are few to no flaws and weaknesses in the procedure itself. Butane was discovered by Dr.
The largest error in this experiment is in determining the mass of the lighter. Place used towels and plastic wrap with ordinary solid trash. When the lighter was weighed for the next trial, the weight was slightly off due to the existing water inside the lighter. Position the lip 1-2 cm below the water surface. Some of our calculators and applications let you save application data to your local computer. Molecular weight is represented by the same number in all unit systems regardless of the system used.
Teachers Guide Purpose To determine the molar mass of the butane in a disposable cigarette lighter. Systematic errors usually occur from faulty equipment. Also, the butane used in the experiment could have been certified as pure butane, rather than butane from a common lighter. Precautions Remove flames or other ignition sources from the laboratory. Make weighings to the nearest 0. For bulk stoichiometric calculations, we are usually determining molar mass, which may also be called standard atomic weight or average atomic mass.
Students should not be allowed to play with the lighters. This is not the same as molecular mass, which is the mass of a single molecule of well-defined isotopes. Formula weights are especially useful in determining the relative weights of reagents and products in a chemical reaction. Collect about 80 mL of gas in a 100-mL graduated cylinder. Another systematic error was that if the beaker was even slightly cracked at the top, allowing air to enter the beaker, the value of molar mass would change because the gas collected at the top of the beaker would no longer be strictly butane. We don't save this data.
We tested the accepted value by calculating the molar mass of butane in a butane cigarette lighter. Cookies are only used in the browser to improve user experience. What is the percentage error between your value and 22. Description A sample of butane gas isobutane is obtained from a disposable cigarette lighter. We don't collect information from our users.