Analytical Chemistry Test Questions – Flashcards
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| Molarity (M) |
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| mol / L total solution |
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| Molality (m) |
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| mol solute / kg solvent |
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| weight % |
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| (mass analyte / total mass) x 100 |
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| ppm |
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| mg / L (mass analyte / mass tot soln) x 10^6 |
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| ppb |
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| (mass analyte / mass tot soln) x 10^9 |
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| ppt |
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| g / L (mass analyte / mass tot soln) x 10^3 |
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| Schlieren Effect |
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| indicies of refraction cause a solution to look oily if it is not well mixed |
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| Bad Primary Standards |
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| -Na2CO3 -H2SO4 -HCl |
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| Systematic Errors (Determinate) |
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| reproducable |
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| Random Errors (Indeterminate |
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| Gausian disstribution |
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| Accuracy |
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| how close to the correct value (error) |
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| Precision |
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| how consistent you are (deviation) |
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| absolute error |
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| mean -actual value |
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| Relative Error |
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| actual error/ actual value |
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| absolute deviation |
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| result - mean |
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| Average Deviation |
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| (?|x-mean|)/ N |
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| Rel. Avg. Dev. |
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| [(?|x-mean|)/ N ] / mean |
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| Std. Dev. |
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| v {[?(x – mean)^2] / N-1} |
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| aA + bB --> cC + dD Find Keq |
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| [C]^c x [D]^d / [A]^a x [B]^b |
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| Combine H2CO3 --> H+ + HCO3- Keq1 HCO3- --> H+ + CO32- Keq2 |
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| H2CO3--> 2H+ + CO3 2- Keq = (Keq1)(Keq2) |
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| Reverse: H2CO3 --> H+ + HCO3- Keq1 = 4.45x10^-7 Keq = (Keq1)(Keq2) |
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| HCO3- + H+ --> H2CO3 Keq= 1/Keq1 = 2.25x10^6 |
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| Order of precipitation |
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| smaller Ksp precipitates first |
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| Common Ion Effect |
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| a salt will be less soluble if one of its constituent ions is already present in the solution |
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| Acids and Bases Arrhenius Bronsted-Lowry Lews |
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| H+ and OH- H+ donar and H+ acceptor e- acceptor and e- donar |
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| Strong Acids |
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| HCl HNO3 H2SO4 HClO4 HBr HI |
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| Weak Acids |
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| HOAc Carboxylic Acids HF H2S H3PO4 H2CO3 |
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| Strong Bases |
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| NaOH KOH LiOH |
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| Weak Bases |
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| NH3 R-NH2 |
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| Find Kb NH3 + H2O --> NH4+ + OH- |
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| Kb = [NH4+]x[OH-] / [NH3] |
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| Kjeldalhl For N (volumetric) |
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| -sample placed in boiling H2SO4--> NH4+ + CO2 + H2O -add excess base to convert NH4+ --> NH3 -distill the NH3 into a known conc. of HCl (some of the HCl will be neutralized, but not all) -titrate the excess HCl with NaOH -the difference in moles correlates to the moles of NH3 consumed |
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| What is the end point? |
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| observed in lab --> color change |
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| What is the equivalence point? |
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| mol of titrant = mol of anlayte |
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| ionic strength |
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| 1/2 ?CnZn^2 = µ C=Concentration Z=Charge |
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| Activity of M |
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| AM = [M]?M |
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| Debye- Huckle Equation (for calculating ?) |
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| log? = (-0.51 x z^2vµ) / (1 + {[?vµ]/305}) ? = activity coefficient z = ion charge µ = ionic strength in [M] ? = hydrated ionic raiums in ppm |
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| Thermal Expansion |
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| (conc1/ dens1) = ( conc2/ dens2) [M]( 1 ± coeff. of therm. expan)(? temp)= |
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| Comparing an answer with the accepted answer within a specified confidence limit of a small data set (replication of a measurement with one overall mean and standard deviation) |
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| Use the Confidence Interval: µ = [m ± (ts)] / vn look up t value for whatever degrees of freedom your data has (df = n-1) |
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| Comparing two different methods to see whether they agree with each other within a specified confidence limit. Measuring a qunatity multiple times with different methods; each data set has its own mean and standard deviation. |
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| tcalc = |m1-m2| / spooled calculate this t and compare to a t value from the table |
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| Comparing whether 2 methods agree with each other when a sample is measured once by one method and then again by another. Then different sample is measured once by method 1 and once by method 2. This is repeated for n different samples |
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| 1.Standard Deviation of the differences: sd=v( [? (di - d)^2] n-1 ) di=difference between two methods d= mean of the differnces 2. tcalc=(|d|/sd) v n |
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| variance |
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| s^2 (s=std. dev) |
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| coefficient of variation (relative standard deviation) |
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| (s/m) x 100 |
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| Standard Error of the Mean |
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| s / vn |
