oo T-Mobile * 80% 10:07 AM bb-csuohio.blackboard.com . Bssureyesusaaseerendemnda
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oo T-Mobile * 80% 10:07 AM bb-csuohio.blackboard.com . Bssureyesusaaseerendemndaselease rekr to your laboralory book, Chaper 4, page 50-1 for directions on cleaning a'dMg gless sureAkonox solution will be available for wahng the · Wide mouth glassware such as beakers can be dried out using paper towels Nanow mouthed glassoware such as cylinders can be dried by air flow after rinsing with aceione, Pipenes can be rinsed 2-3 times with the liquid to be measured prior the real measurement Acetone must be disposed on OrlaWaste on furne hood; maler only can be digosed nk, Paper towels and weighing boats or weighing paper can be disposed on the egular arbuge solid chemicals must be disposed on solid waste container on fume hood Glassware must be washod at the end of he experiment (alconox, rime with watcr, one rise with acetone Lek all ofyour glassware and retum your keytothe istractor / teaching assistant * EACH GROUP MEMBER IS RESPONSEBLE FOR RECORDING THE OBSERVATIONS ON HISHEROWNLAR NOTEBOOK Materials:1)10 ml cylindar (2)clean pasteur pipettes (* be surethg tipsofthe ppenes arg not broken when starting the ) beaker with with distilled water Using your pastcur pipctte to add distilled water to a cylinder in a dropwise manner. Be sure to not lot liquid droplets on the walls of the cylinder, as it will not couns toward the reading volume and can affect your measurements. Add full drops of water until the menisous reach the 1 mL mark on the cylinder. Do not worry if the meniscus is not exactly en the 1 mL mark. Recoed the number ef deops necessary for reaching the mark of I ml, making sure to mote if the meniscus is not exactly on I ml. Dispose of the liquid dry your glassware and repeat the procedure using the same pastcur pipetic. Then, exchange your pastour pipctic and rapeat the procedure another time. Does the number of water drops from two individual pipettes are equivalent or nearly Carefully, break the tip ofboth your ppenes. Itis not a problem ifthey are not beuken·athe samespal Now repeat the above procedure one1) time with each pipette Does the number of waterdropkt!ecessary for reaching 1 ml. change compared to the unbroken pipettes? Write your conclusion on yeour lab nosehook Note some linders do not have the caibration for very smal solsmes (oach as /ml or sometimes it e hard to monitor the meniscus for suchasmalt volume. Ie is not problem to keep adhagdropscfwaknD higher calbnation ark Just make sure yow "cancalate back the nsmber of dnes you noed for 1 ml. For example: Assnme student record 45 dropsefdistilled waterfor reaching eke mork of 3 ml. Therefore, for 1 mL, we shall have: 45 drops + 3 mL-15drops /mL. Materials(a balance (1) spatula (1) small beaker to roceive the wciphod solsd Weighing paper sodium chloride solid Safety netice Please notice war it is a safety rear to wak arond the lab with welghed reagents in paperso weighing boats, evew if the cheminal is a non-kazard swch as sodiun chloride. The chemical can be spilied in the ground or bewches during your wak or by bumpieg into a lab me, cnsing and ncessay contamination of sufaces, potenally the skin so o say the loss of solid easared Jor your esperimest Be sure your receiving Masbcaker s on te side of the baiance whew easaring solids Be sure your balance is clean and tared. If balance is dirt, motify your instructor immodianly Place a weighing paper in the balance WITHOUT FOLDING the paper Close all the side doors of yeu balance. Tare the balance. Weigh 1.00:0.1 g of sodium chloride. Record your mass in your motchook. Lift the paper plus solid and transfer the mass to a beaker. Observe for spills. N aay sills occur, sonty yowr TA or isstructor iediaely Spills can affect abe precision of measurements and wwst, enfore, be cleaedExplanation / Answer
1) If the average value of different measurements is close to the correct value, the measurement is said to be accurate(the individual measurements may not be close to each other)
If the value of different measurement are close to each other and hence close to their average value the measurement is said to be precise(the average value of different measurement may not be close to the correct value).The precision depends on measuring device as well as skilll of the operator.
The difference between precision and accuracy is that accuracy is measurement of agreement between an experimental result and the true value of the given quantity.Precision on other hand measure the agreement between several experimental results obtained from the same quantity under identical conditions.
Accuracy is expressed in terms of absolute errors or relative errors whereas precision is expressed in terms of various types of deviations from the mean.
2) 1+0.1 = 1.1 and 1-0.1 = 0.9 means 1.1 to 0.9 are accurate range for this measurement
3) Always read the level at the bottom of the meniscus.This is more accurate and precise method than beakers.Always look straight from the side of the meniscus at the graduated cylinder to measure the volume(Never try to read from above and below).
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