CHM 113 LAB FINAL STUDY GUIDE
QUESTIONS & ANSWERS CORRECT
100%
MOLE - ANSWERStandard scientific unit for measuring large quantities of very small
entities such as atoms, molecules, or other specified particles. 6.022× 10^23.
Molecular Weight - ANSWERMass of molecule. Use periodic table to get molecular
mass and then multiple by how many moles in it to get molecular weight.
Molarity - ANSWERMoles of solute divided by liters of solution.
Significant Figures - ANSWERNon-zero digits are always significant.
Any zeros between two significant digits are significant.
A final zero or trailing zeros in the decimal portion ONLY are significant.
Density - ANSWERMass/Volume
Precision vs. Accuracy - ANSWERAccuracy is the how close a measured value is
to the actual (true) value. While, precision is the repetition of measurements under
unchanged conditions and shows the same results. The more precise and accurate
a
measurement is, the less error with density calculations expressed, using significant
figures.
Mole ratio - ANSWERMol water/ Mol anhydrous salt. This is done by evaporating the
water from the hydrate and measuring how much moles of water to salt there is.
How Much Water is in the Hydrate? - ANSWERThe purpose of this lab was to
understand how much water was in a known and unknown hydrate and determine
the empirical formula. This was done by taking the initial mass, heating the hydrate,
then cooling and weighing it.
Beer-Lambert's Law - ANSWERA = ebC, where e is a proportionality constant called
the molar absorptivity that is specific for the
absorbing species, b is the thickness of the solution in the light path (usually
constant for an
experiment), and C is the molarity of the absorbing species in the solution.
What is a standard curve/how can be used to find concentration? - ANSWERFor a
given light-
absorbing species, a plot of absorbance versus concentration should give a straight
line. This
straight-line relationship can be used to determine the concentration in an unknown
solution of
, the species tested.
Absorbance vs Transmittance - ANSWERAbsorbance has an inverse relationship
with transmittance. Transmittance is how much light passes through solution.
Absorbance is how much light is absorbed in a solution.
Percent Error - ANSWERSubtract the accepted value from experimental value then
divide by accepted value.
Solubility rules - ANSWERThe 3rd row reference to I
−ion tells us that, while most iodide
compounds are soluble (dissolve in water), PbI2
is one of the
exceptions.
We can therefore conclude that Pb2+ and I
−ions will combine
to form an insoluble compound, a precipitate.
Single Displacement - ANSWERis a type of chemical reaction where an element
reacts with a compound and takes the place of another element in that compound.
Pure elements.
Double Displacement - ANSWERoccur when parts of two ionic compounds are
exchanged, making two new compounds.
Balanced chemical/ ionic/ net ionic equations - ANSWERMolecular equation
(Exchange Reaction)
Ionic equation (write soluble electrolytes as separate
ions - be sure to maintain ion charge ratio)
Net ionic equation (omit spectator ions)
Properties of acids and bases - ANSWERWhen acids dissolve in water, the cation
formed
is an H+
(aq) ion. When bases dissolve in water, the anion formed
is an OH−
(aq) ion.
First Law of thermodynamics - ANSWEREnergy can be transformed from one form
to another but neither created or destroyed
q = m x C x ∆T - ANSWERThe relationship between heat change and temperature
change. q is the heat change (joules, J)
• m is the mass (grams, g)
• ∆T is the temperature change, Tfinal - Tinitial (
◦C)
• C is the specific heat for that substance (J/(g
◦C))
QUESTIONS & ANSWERS CORRECT
100%
MOLE - ANSWERStandard scientific unit for measuring large quantities of very small
entities such as atoms, molecules, or other specified particles. 6.022× 10^23.
Molecular Weight - ANSWERMass of molecule. Use periodic table to get molecular
mass and then multiple by how many moles in it to get molecular weight.
Molarity - ANSWERMoles of solute divided by liters of solution.
Significant Figures - ANSWERNon-zero digits are always significant.
Any zeros between two significant digits are significant.
A final zero or trailing zeros in the decimal portion ONLY are significant.
Density - ANSWERMass/Volume
Precision vs. Accuracy - ANSWERAccuracy is the how close a measured value is
to the actual (true) value. While, precision is the repetition of measurements under
unchanged conditions and shows the same results. The more precise and accurate
a
measurement is, the less error with density calculations expressed, using significant
figures.
Mole ratio - ANSWERMol water/ Mol anhydrous salt. This is done by evaporating the
water from the hydrate and measuring how much moles of water to salt there is.
How Much Water is in the Hydrate? - ANSWERThe purpose of this lab was to
understand how much water was in a known and unknown hydrate and determine
the empirical formula. This was done by taking the initial mass, heating the hydrate,
then cooling and weighing it.
Beer-Lambert's Law - ANSWERA = ebC, where e is a proportionality constant called
the molar absorptivity that is specific for the
absorbing species, b is the thickness of the solution in the light path (usually
constant for an
experiment), and C is the molarity of the absorbing species in the solution.
What is a standard curve/how can be used to find concentration? - ANSWERFor a
given light-
absorbing species, a plot of absorbance versus concentration should give a straight
line. This
straight-line relationship can be used to determine the concentration in an unknown
solution of
, the species tested.
Absorbance vs Transmittance - ANSWERAbsorbance has an inverse relationship
with transmittance. Transmittance is how much light passes through solution.
Absorbance is how much light is absorbed in a solution.
Percent Error - ANSWERSubtract the accepted value from experimental value then
divide by accepted value.
Solubility rules - ANSWERThe 3rd row reference to I
−ion tells us that, while most iodide
compounds are soluble (dissolve in water), PbI2
is one of the
exceptions.
We can therefore conclude that Pb2+ and I
−ions will combine
to form an insoluble compound, a precipitate.
Single Displacement - ANSWERis a type of chemical reaction where an element
reacts with a compound and takes the place of another element in that compound.
Pure elements.
Double Displacement - ANSWERoccur when parts of two ionic compounds are
exchanged, making two new compounds.
Balanced chemical/ ionic/ net ionic equations - ANSWERMolecular equation
(Exchange Reaction)
Ionic equation (write soluble electrolytes as separate
ions - be sure to maintain ion charge ratio)
Net ionic equation (omit spectator ions)
Properties of acids and bases - ANSWERWhen acids dissolve in water, the cation
formed
is an H+
(aq) ion. When bases dissolve in water, the anion formed
is an OH−
(aq) ion.
First Law of thermodynamics - ANSWEREnergy can be transformed from one form
to another but neither created or destroyed
q = m x C x ∆T - ANSWERThe relationship between heat change and temperature
change. q is the heat change (joules, J)
• m is the mass (grams, g)
• ∆T is the temperature change, Tfinal - Tinitial (
◦C)
• C is the specific heat for that substance (J/(g
◦C))
