EXP 1: Precision & Accuracy
Define accuracy and how it is reported
What is how closely an experimental value approaches the true value, and percent error?
*for extra studying, write down the equation for percent error
The type of quantitative chemical analysis that relies on the measurement of mass, and the general method has many applications in chemistry.
What is gravimetric analysis?
*for extra studying, write down the disadvantages of gravimetric analysis
The type of chemical analysis that relies on the measurement of volume (how acid-base and reduction-oxidation (redox) reactions are studied)
What is volumetric analysis?
The analytical method of analyzing the iron composition in the Fe3+ oxalate compound.
What is spectrophotometry (the method based on the interaction of light with matter)?
*for extra studying, draw and label the components of a spectrophotometer
Name the range of visible light in the electromagnetic spectrum.
What is 400-700 nm?
*for extra studying, draw out the entire electromagnetic spectrum with indicated colors and wavelengths
Define precision and how it is reported
What is the reproducibility of a measurement and how close the results are to one another regardless of whether the measurements are accurate or not, and statistical analysis (i.e. standard deviation)?
*for extra studying, write down the equations for sample and population standard deviation and note the differences between them
A compound that consists of at least one metal ion (usually a transition metal) and ligand, and may have an overall charge that is positive, negative, or zero (neutral) depending on the overall charge determined by the sum of the charges on the metal ion and all of the ligands bound to the metal ion.
What is a coordination compound?
*for extra studying, list which part of the compound is a Lewis acid and which part of the compound is a Lewis base
The two ways to determine the exact concentration of the titrant/standard solution.
What is measuring the mass of the solid component in the titrant and carefully diluting it to a known volume OR standardization by titrating the solution with a primary standard?
*for extra studying, identify the method that has a high accuracy and precision (hint: we used in experiment 3)
Write the equation for transmittance.
What is T = I_t / I_0 ?
Transmittance is the ratio of the intensity of light that is transmitted through the sample cell (I_t) to the intensity that is incident on the sample cell (I_0).
*for extra studying, write the equation for absorbance using the transmittance equation
Define wavelength and frequency.
What is the distance between two successive crests (wavelength) and the number of waves passing a given point in one second?
*for extra studying, write down the equation connecting wavelength, frequency, and the speed of light
A reproducible, and therefore precise, experiment will have a small standard deviation compared to the average value. The ratio of the standard deviation to the average value of all n trials is quantified through this equation.
What is percent relative standard deviation (RSD)?
*for extra studying, write down the RSD equation
Examples of neutral ligands that donate a single pair of electrons to the metal ion (monodentate)
What is water and ammonia?
*for extra studying, list some and define multidentate ligands/chelators (hint: a chemical in experiment 2)
The difference between equivalence and endpoint.
What is the method to determine the point when number of moles of the acid and the base have been (equivalence/stoichiometric point) and the method of using an indicator dye that causes a visible color change of the solution at a certain pH (endpoint)?
*for extra studying, write about the experimental conditions needed to best determine the equivalence point
Write out and define the variables of the Beer's law equation
What is 𝐴=𝜀(𝜆)𝑏𝑐 where 𝐴 is absorbance, 𝜀 is molar absorptivity, 𝜆 is wavelength, 𝑏 is path length, and 𝑐 is concentration?
*for extra studying, write down the units for each variable
Name the two key principles of quantum mechanics.
What is wave-particle duality and quantization?
*for extra studying, define these principles and name experiments that support each principle
List the three glassware used in experiment 1, and the impact of large trials on your data?
What is beaker, graduated cylinder, and volumetric pipet, and a larger data set increases precision and reduces random error?
*for extra studying, look back at your results for individual vs. group data for the graduated cylinder
Describe the protonation states of 8-hydroxyquinoline.
What is 8-hydroxyquinoline has two pKa values, with the amino group (NH) of the molecule being a protonated cation below pH 5, the neutral species being between pH 5 and 10, and the alcohol (OH) group deprotonating and becoming an anion above pH 10?
*for extra studying, describe how the protonation states have an affect on the solubility and binding of aluminum
From this equation, determine the Ka expression:
HA + H2O ⇄ A- + H3O+
What is Ka = [H3O+] [A-] / [HA]?
*for extra studying, write down the Henderson-Hasselbalch equation and the Henderson-Hasselbalch equation when the moles of acid equal the moles of base
The plot used to determine the concentration from absorbance.
What is a calibration curve?
*for extra studying, do the calculation to determine concentration using the calibration plot you made
Write out the equation for the energy of a photon and define the variables.
What is E = hv ? The E is the photon energy, the h is Planck's constant, and the v is frequency.
*for extra studying, write out the units of each variable and relate this equation to the wavelength
Converting mass of water to volume of water through this property.
What is the density of water as a function of temperature?
*for extra studying, look back at the equation that you used to convert the mass of water to the volume of water
This contamination will result in impure precipitate that is a combination of both solid hq and Al(hq)3, and will lead to an artificially ___ calculated concentration of Al3+.
What is hq (Equation 2-2) has limited solubility in water, and a large excess will result in hq contaminating the Al(hq)3 precipitate, which would lead to an artifically high calculated concentration of Al3+?
*for extra studying, read up and understand other potential assumptions about the experiment
Name the benefits of a pH probe
A pH probe is an ion-selective glass electrode which is sensitive to the concentration of H3O+ in solution. Advantages are operation over a wide pH range (pH 1-12), little interference from oxidizing and reducing agents, fast response, and accuracy.
*for extra studying, go through all of the stoichiometry needed to determine [NaOH], mass of unknown acid, and molar mass in your experiment
Explain the reasoning behind the wavelength selection.
What is wavelength should correspond to the maximum absorbance of the analyte for maximum sensitivity and precision?
*for extra studying, explain why the maximum absorbance of Fe(II)-bipyridine is at 520 nm (hint: think about complementary colors)
The reason why energy levels of helium is harder to understand than hydrogen.
What is the presence of one additional electron in helium compared to hydrogen makes helium a much more difficult system and one that cannot be solved exactly, stemming from the interplay between electron-electron and electron-nucleus interactions (shielding)?
*for extra studying, understand Balmer's formula and the Bohr model and how they relate to one another in context of the hydrogen atom