Chemistry exam lab
Be able to sketch the filtration set-up used to isolate the product.
(Yes)
enthalpy of neutralization
(moop)
spectrophotometer
An instrument used to study the response of solutions to light. It has two scales one calibrated to display percent transmittance and the other calibrated to display absorbances.
valence shell electron pair repulsion theory,
Assumption that the outermost or valence electrons is an atom whether bonding or nonbonding tend to orient themselves to form specific geometric patterns that minimize their mutual repulsions.
-Be able to calculate the available electrons (AE), needed electrons (NE), and draw the Lewis dot structures for a given molecule.
CO2 VE equals 6 NE equals 4 BE equals 4 We now substitute the values, and we have: 6 - 4 - 4/2 = 0 The formal charge of oxygen (on the right) equals 0
Percent yield
Calculated from the actual and theoretical yield.
reference solution (blank)
Contains all components of the solution except the species being determined.
calorimeter constant
Determine indirectly the amount of heat absorbed by the calorimeter per degree rise in the temperature of the contents of the calorimeter this amount of heat is called the calorimeter constant or the heat capacity of the calorimeter which is expressed in joules per degree (J deg^_1)
-Calculate the formal charge of atoms within a Lewis structure and use this information to select the best Lewis structure representation of the molecule.
Ex: OF2 ~~~~~~~~ AE:20e O=6v F=7V (2)=14 Total: 20 ~~~~~~~~~ NE: 2(0)+8(3)-2(3-1)=20-e ~~~~~~~~~~~~~~~~~~~~~ Lewis Structure: F(8)-O(4)-F(8) ~~~~~~~~~~~~~~~~~ VSEPR Sketch: Bent 1 O: A 2 F: B2 2 lines ~~~~~~~~~~~~~ Geometry Descript: AB2N2 ~~~~~~~~~ Bonding Descript: 2O-F sig bonds.
ground state
Having single electron in orbit closet to the nucleus.
enthalpy
Heat energy transferred us expressed in terms of enthalply. The change of Enthlaply (Triangle H) is the difference between the enthalply of the profucts and that of the reactants at constant pressure.
molar absorptivity
Known as the sensitivity factor, it is proportionally constant of a particular absorbing species with units of L mol^-1 cm^-1
Beer's law plot.
Linear relationship between concentrations and absorbance shown in figure 1 is typical of many chemical systems that are said to follow Beer's law. This plot of absorbance versus concentration is referred to as __________.
List some reaction conditions that may result in an actual yield less than the theoretical yield.
Loss of precipitate from not filtering properly, using water to wash the product back into the beaker.
electrons
Negatively charged particals
-Be familiar with equations 1 and 2 listed on the first page of the lab. Know the colors associated with various chemical species. For equation 2, be able to identify the oxidizing agent, reducing agent, oxidized species, and the species that is reduced.
OCI^- (aq, colorless) +21^-1 (aq,colorless)+2H3O^+ (aq)----->I2 (aq,brown)+CI^-1 (aq,colorless)+3H2O (l) /////////////////////////// The reaction in Eq proceeds to completion. Visible evidence of reaction is the change in appearance of the solution from colorless to brown, due to formation of iodine. In the presence of excess I^- ion the amount of I2 formed is a measure of the amount of OCI^- ion reacting. Then we determine the amount of I2 formbed by titrating the I2 with a standard sodium thiosulfate solution (Na2S2O3). The titration reaction for this experiment is shown in Eq 2. ///////////////////// I2 (aq,brown)+S2O3^2- (aq,colorless)---->2I^- (aq,colorless)+S4O6^2- (aq,colorless) (PAGE 153-154)
Given Table 1 be able to draw a VSEPR sketch.
Page 210 Molecular Geometry and building Ex: AB2: A is in the middle one B at each end of the A attached by lines. Ex: ABN: A in the middle line with two dots at end B on the other side. Ex: AB3: A in the middle two B on each end of a and a line extending with two dots.
Filtrate
Percipitate is filtered from the supernate the liquid passing through the funnel.
, protons
Positively charged particals.
Decantation
Process of pouring the supernatant into the funnel assembly without disturbing the precipitate that has started to settle at the bottom of the beaker.
Theoretical Yield
Product from the reaction.
Stiochiometry
Quantative relationship among the amounts of reactants and products.
Calorimeter
Reactions that are carried out in well-insulated containers.
cuvette
Sample containers uniform in size.
Superannuate Liquid
Solution above the precipitate
Write a balanced chemical equation corresponding to the formation of the strontium iodate monohydrate in lab.
Sr(NO3)2 + 2KIO3 —-> Sr(IO3)2 + 2KNO3 check
thermochemistry
Study of heat changes and transfers associated with chemical reactions.
Limiting Reactant (reagent)
Substance that is completely used in the reaction.
excitation
The process of energy absorption.
analytical wavelength
Wavelength used for analysis.
Given the molarities and volumes of two reactants, be able to identify the limiting reagent and calculate the theoretical yield.
What is the theoretical yield of CaO if 24.8g of CaCO3 is heated? CaCO3=24.8g (MM-100.1g) CaO=56 MM 24.8g CaCO3 x 1/100.1x1/1x56/1=13.9g CaO Theo Yield=13.9 Limiting Reagent is the first compound/element in the equation.
Be able to explain how the calorimeter constant was determined experimentally for this experiment.
You will measure the temperature of two known volumes of water, one which is hot while the other cold for a period of 5 minutes. After both have been measured both cups will be mixed and the temperature will be measured over a period of 15 minutes. (All this is determined by a Styrofoam cup)
aliquot
a portion of a larger whole, especially a sample taken for chemical analysis or other treatment.
hybrid orbitals.
orbitals that are a combination of the originals s,p,d orbitals.
Be able to perform all the calculations listed in the lab manual.
page 154-158
Explain how the endpoint is made more distinct for this titration, list the indicator used and the color change that occurs.
page=154//// As the titration proceeds the I2 concentraion in the solution decreases. This causes the solution color to change from brown to pale yellow near the end of titration. The END POINT occurs when all the I2 has reacted and the solution is colorless, because the change from pale yellow to colorless is not very distinct, establishing the end point on the basis of this final color is challenging. We can make the end point MORE DISTINCT by adding small amount of STARCH Solution to the titration mixture when the solution turns pale yellow.
Calculate the calorimeter constant, heat gained by calorimeter, heat gained by contents, total heat absorbed and the H for the reaction.
pg 134-137
-Be able to identify and label the key parts of Fig. 4 (Tfinal, Thotinit, Tcoldinit, Tcold, Thot, and the line of mixing).
pg 135
valence bond theory
two atoms are covalently bonded if a pair of electrons occupies the area defined by the overlap of atomic orbitals from the two atoms.
oxidation-reduction reaction
type of chemical reaction that involves a transfer of electrons between two species. An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron.