Comprehensive Chemistry Exam Preparation Guide, Exams of Chemistry

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CHM 2045 L UF 2024/2025 LAB

EXAM QUESTIONS WITH 100%

ACCURATE ANSWERS.

Percent error formula -- Answer ✔✔ calculated value minus expected value l value divided by expected value times 100 Find density given unknown concentration graph y=mx+b -- Answer ✔✔ y is density and x is mass % so sub value of y to find x Density formula -- Answer ✔✔ mass/ volume Hydrate definition -- Answer ✔✔ crystalline compound in which one or more water molecules combine with formula unit of walt that loses water above 100c % water= mass water lost/ mass hydrate times 100 -- Answer ✔✔ Mass water lost= -- Answer ✔✔ unheated mass minus mass after heating PH2= -- Answer ✔✔ ptotal - pvapor Ptotal= patm-pfluid -- Answer ✔✔ h1d1=h2d2 -- Answer ✔✔ p1v1/t1=P2V2/T2 -- Answer ✔✔ Molarity= moles/volume in L -- Answer ✔✔

Q= -- Answer ✔✔ mCgDelta T Q is the symbol for heat transfer, m is the mass of the substance, and ΔT is the change in temperature. The symbol c stands for specific heat and depends on the material and phase Lowest energy color -- Answer ✔✔ red Smallest electronic transitions -- Answer ✔✔ lowest atomic # Highest energy color is -- Answer ✔✔ violet molality= -- Answer ✔✔ moles/kg Calculate i= -- Answer ✔✔ mass particles/ moles compound dissolved Accuracy - -- Answer ✔✔ A description of how close a measurement is to the true value of the quantity measured. Precision - -- Answer ✔✔ a measure of how close a series of measurements are to one another sig figs for addition and subtraction - -- Answer ✔✔ the result has the same number of decimal places as the measurement with the fewest decimal places sig figs for multiplication and division - -- Answer ✔✔ the result has the same number of sig figs as the term with the least number of sig figs density formula - -- Answer ✔✔ D=m/v percent error formula - -- Answer ✔✔ |accepted value-measured value| / accepted value x how to take a proper measurement - -- Answer ✔✔ record the measured value plus one estimated digit

how to take a proper liquid measurement - -- Answer ✔✔ read from the bottom of the meniscus mass percent of solute - -- Answer ✔✔ mass of solute/mass of solution x 100 ALSO mass of solute / (mass of solute + mass of solvent) x 100 independent variable is graphed on the - -- Answer ✔✔ x-axis dependent variable is graphed on the - -- Answer ✔✔ y-axis finding moles - -- Answer ✔✔ (total grams) / (molar mass) = moles mass percent of water - -- Answer ✔✔ (grams of water lost) / (grams of hydrate before it was heated) x 100 reduction - -- Answer ✔✔ gaining electrons oxidation - -- Answer ✔✔ loss of electrons How does titration work? - -- Answer ✔✔ Fill a burette with a known volume of an alkali, at a known concentration. Make sure the acid is in an aqueous solution at a known volume, and get it into a beaker with a pipette. Add an indicator to the acid (phenolphthalein), and begin to drop the alkali in from the burette, until the solution has turned permanently pink, indicating that the acid is now neutral. Record the volume of alkali added. Titrant - -- Answer ✔✔ A solution usually of known concentration that is used to titrate a solution of unknown concentration (added to the analyte) Analyte - -- Answer ✔✔ Substance being analyzed, usually of unknown concentration equivalence point - -- Answer ✔✔ the point at which the two solutions used in a titration are present in chemically equivalent amounts

end point of titration - -- Answer ✔✔ when the titration ends (the point at which the indicator changes color) Ideal Gas Law - -- Answer ✔✔ PV=nRT (n is equal to the number of moles of the substance and R is the gas constant 0.082) STP (standard temperature and pressure) - -- Answer ✔✔ conditions of 0.00°C (273 K) and 1 atm pressure calorimetry equation - -- Answer ✔✔ q=mcdeltaT Hess's Law - -- Answer ✔✔ the overall enthalpy change in a reaction is equal to the sum of enthalpy changes for the individual steps in the process q of the system = - -- Answer ✔✔ -q surroundings q of reaction = - -- Answer ✔✔ -q solution specific heat of water - -- Answer ✔✔ 4.184 J/gC delta H of a reaction - -- Answer ✔✔ sum of delta H products - sum of delta H reactants Beer's Law - -- Answer ✔✔ A=ebc What does each letter represent in A=ebc - -- Answer ✔✔ A is absorbance, b is path length (length of cuvette in cm), e is molar absorptivity, c is concentration when volume of a solution changes, its new concentration can be determined by - -- Answer ✔✔ m1v1 = m2v rate = - -- Answer ✔✔ k[A]^m[B]^n Energy of a photon equation - -- Answer ✔✔ E=hv where h=6.626E- and v=frequency

formal charge equation - -- Answer ✔✔ valence electrons - sticks and dots The empirical formula of the hydrate can be found by determining x in the formula salt.xH2O. X is found by comparing moles of water lost to moles of anhydrous salt remaining: -- Answer ✔✔ (moles water)/(moles anhydrous salt) = x Titrant: -- Answer ✔✔ the substance being added to the analyte. In this case the Ce4+ solution is the titrant, being added via micropipette. The titrant usually is of known concentration. Analyte: -- Answer ✔✔ the substance being analyzed. Often of unknown concentration. In this case, the Fe2+ solution is the analyte. Equivalence point: -- Answer ✔✔ the point at which the titrant and analyte are present in a stoichiometric equivalent ratio based on their reaction. End point: -- Answer ✔✔ where the titration ends in reality. If you're using a visual indicator, this would be where you would observe the completion of the reaction. If using an indicator, you would choose one such that the end point is as close as possible to the equivalence point. This reaction is somewhat self-indicating - the color of the combined reagents should become slightly yellow as excess Ce4+ becomes present. Titration curve: -- Answer ✔✔ this can be a pH vs volume curve, showing change in pH as titrant is added, for an acid/base reaction. Or, as in this case, it can be a graph of potential vs volume of titrant added. There are other options, as well, such as conductance vs volume. The Ideal Gas Law has the formula: -- Answer ✔✔ 𝑃𝑉=𝑛𝑅𝑇 R is the Gas Constan -- Answer ✔✔ t 0.

Pgas = -- Answer ✔✔ Patm - Pfluid. The pressure exerted by a fluid due to gravity can be calculated by the equation: -- Answer ✔✔ 𝑝=ℎ𝑑𝑔 1 atm mmhg -- Answer ✔✔ = 760 mmHg 1 atm torr -- Answer ✔✔ = 760 Torr 1 atm pa -- Answer ✔✔ = 101325 Pa 1 atm mbar -- Answer ✔✔ = 1013 mbar Transmittance (T) is the fraction of light at a given wavelength that passes through a light-absorbing medium. Transmittance is defined as: T=I/Io -- Answer ✔✔ When no light is absorbed, I = ___ and A=0 -- Answer ✔✔ I0 and A = 0. Beer lambert law -- Answer ✔✔ absorbance= molar absorptivity times distance in cm times concentration These are usually strong electrolytes and can be expected to 100% dissociate in aqueous solution. -- Answer ✔✔ ionic These are usually non-electrolytes. They do not dissociate to form ions. Resulting solutions do not conduct electricity. -- Answer ✔✔ molecular compounds These are molecules that can partially or wholly dissociate, depending on their strength. -- Answer ✔✔ molecular acids Formal Charge = -- Answer ✔✔ [# of valence electrons on atom] - [non-bonded electrons + number of bonds]. Vant hoff factor is -- Answer ✔✔ i