The volume of hydrogen gas produced will be measured directly on the scale of a gas-measuring tube. This was done using a balance. Weigh the flask, cap, and condensed vapor. The difference in the initial and final volume of water was the volume of gas released. The method required the water to have a temperature between 17°C and 30°C, however the actual temperature was only 14°C. The substance inside the lighter is a liquid, before a phase change occurs that changes it into a gas. Based on our calculations, the molar mass of the gas was 125 grams per mole.
You subtracted the partial pressure of water, converted and used the right units, worked through the equation properly, and all my calculations match yours. When it is divided by the number of moles the molar mass will decrease. This number was found by using tools to measure the values for volume, temperature, and mass. What was your set-up for collecting the butane from the lighter? The equation was solved for n, number of moles of gas. Determine the empirical formula of butane based on your data.
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. Another systematic error that could have occurred is that the ambient room pressure was taken from a website dictating the pressure in the area, rather than directly in our room. It was important that all of the air bubbles be removed from the jar using various methods. The water caused the lighter to have an increased mass, causing an increase in the experimental molar mass of the, leading to a high percentage error. However, if you use your total pressure P H2O + P Butane in the equation, you will end up with a mole value that is the sum of moles H2O and moles butane.
The molar mass would be lower because the difference in the mass of butane released into the jar will be appear to be less. The atmospheric pressure was assume to be standard pressure and the gas was assume to behave as an ideal gas, in order to use the ideal gas law equation. Find the mass of 1 mole of this gas? The lighter had time to dry and then was placed on the balance to be weighed again. Description A sample of butane gas isobutane is obtained from a disposable cigarette lighter. When the lighter was weighed for the next trial, the weight was slightly off due to the existing water inside the lighter. The other values were either provided or constant numbers.
So, if you have 4. If the other gases were not mixed in with the butane the mass would have been lower and the overall molar mass would have been lower as well. I hope you sorted out your problems, but to answer your questions anyway, you shouldn't need to apply sig figs until you find your molecular weight at the very end. DescriptionA volatile liquid with a boiling temperature in the range of 70-90 °C is placed in a small, dry, weighed flask. If Mg was placed too close to the one-hole stopper, some gas escapes with the water as it leaves the gas collecting tube. It can vary between trials of an experiment, and it commonly defined as the deviation from the true accepted value. Place used towels and plastic wrap with ordinary solid trash.
Our meniscus was located above water level in the 100 mL graduated measuring cylinder. Next, each part was placed into the equaiton of collecting gas over water. After filling approximately half the jar with butane gas, the lid was secured tightly to the jar, and the jar removed from the water. In standard temperature and pressure, the alkane would be a gas, but because it is not in standard pressure it causes a phase change inside the lighter. If the lighter was not completely dry when it was weighed the second time, it would cause the molar mass to be higher because the grams would be a larger value.
A thermometer could have been placed inside the cylinder to ensure an accurate temperature. Systematic errors usually occur from faulty equipment. Which is what you did. The butane gas was aired out while the lighter dried. The mass of the lighter was measured using a triple beam balance before it was used in the experiment. My apologies for the wall of text, lol.
I really want take your word for it when you say you. When the Butane is released, it is pushed through a very small hole and released. Tilt the gas-measuring tube slightly. Sig figs for pressure, mass, volume, etc etc, or do I use every decimal that I have gotten with those measurements, and then only do sig figs when I have calculated the molecular weight? T o improve this, a better stopper than our hands could have been used. The jar was taken out from the container and placed on the table with the lid facing up. 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. These gasses had to weigh more to take up the excess space in the jar and account for the excess mass.
However, added all together, the other gases have a higher molar mass. Once again, thanks very much for your in-depth answer! Bonus points: If submitting a picture please make sure that it is clear. Try to think of others. The water vapor pressure depends on the temperature of the water. Also, the air left inside the cylinder might affect the temperature of the butane gas inside the gas collecting cylinder, causing a higher molar mass.
Dalton's law tells you that those are simply additive, i. A triple beam balance was used to determine the mass of the lighter. Then if the angled in was not included in the measurement of the length of Mg then the volume would be to big because you would have an extra piece of magnesium making gas that your where not calculating in. The weakening of the intermolecular forces cause the molecules to spread far apart, forming a gas. It is also important that you describe the specific part of the problem you are struggling with. Because hydrogen has a small atomic mass, the effect on the subscript is large. To determine the molar mass, take the mass of butane in the beaker and divide that by the number of moles of butane.