CHEM 123 - Lab final UBC Questions And Answers Rated A+
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Course
CHEM 123 - Lab UBC
Institution
CHEM 123 - Lab UBC
[A] = -kt + [A]0 - 0th order integrated rate law
1/[A] = kt + 1/[A]0 - 2nd order integrated rate law
accuracy - how close a measured value is to the true value
acid buffer capacity - the number of moles of H3O + per litre of buffer which are required to lower
the pH by 1 unit (units = M)
analy...
CHEM 123 - Lab final UBC [A] = -kt + [A]0 - 0th order integrated rate law 1/[A] = kt + 1/[A]0 - 2nd order integrated rate law accuracy - how close a measured value is to the true value acid buffer capacity - the number of moles of H3O + per litre of buffer which are required to lower the pH by 1 unit (units = M) analytical balance - - used to determine a precise mass to the nearest +/ - 0.0001 g - masses are always reported to 4 decimal places Are you allowed to change the flow rate after you've set it? - no you cannot - it will change the drop size and thus the volume base buffer capacity - the number of moles of OH - per litre of buffer which are required to raise the pH by 1 unit (units = M) beaker - - measuring volumes of liquids and transporting chemicals - not very precise briefly describe the method of initial rates - various reaction rates are measured for multiple experimental trials where the concentration of one reactant is kept constant and the other is changed to determine the order of reaction with respect to the test variable buret - - graduated glass tube with a tap at one end and is used for delivering known volumes of a liquid (good for titrations) - long, graduated, glass tube with stopcock at lowered end and has a tapered glass tip ceramic tile - - for resting hot objects on to cool (protects bench top) - can also be placed under an Erlenmeyer flask during a titration to make it easier to determine the end point Describe the steps for weighing by difference - - place clean empty weigh boat on top loading balance - tare top loading balance & weigh boat to 0.00g - add approximate mass (+/ - 20%) of chemical to weigh boat - close all doors on analytical balance and tare it to 0.0000g - weigh the sample & weigh boat and record the value (1) - transfer weighed sample into beaker (from weigh boat) - weigh the emptied weigh boat and record the value (2) Subtract value 2 from value 1 to get the mass of the chemical describe the steps to take when preparing a standard solution (in a volumetric flask) - - weigh & dissolve the solid compound (using weigh by difference) - clean the volumetric flask, funnel, and stopper 3x with deionized water - quantitatively transfer the dissolved sample into the volumetric flask (using and funnel and rinsing beaker/stir rod with deionized water) - fill volumetric flask to a few centimetres below the calibration mark (do not go above this line) - use a dropper to add water dropwise to volumetric flask until the bottom of the meniscus is resting on the calibration line (if you go past calibration mark, you must start over) - stopper the flask and invert the flask 20x does an analytical balance or top -loading balance need to be recorded to 4 decimal places? - analytical balance drop counter - - has a sensor that counts the number of drops coming out of the drop dispenser - must be lined up with the drop dispenser
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