CHM 144 final Flashcards
when you are graphing data is the x axis the independent or dependent variable?
the independent variable is plotted on the x axis
the variable you are manipulating/ have control over
independent variable
the variable you are measuring/ do not have control over
dependent variable
does the dependent variable go on the x or y-axis?
y-axis (typically, absorbance, pH, temperature)
the most common way to express the precision of a series of measurements
standard deviation
how do you calculate standard deviation?
(sum of absolute deviations^2/ n-1)1/2
how do you calculate absolute deviations?
l mean of the data points - the sum of all the data points l
percent relative standard deviation (RSD%)
(standard deviation/ mean of the data points) *100
standard deviation of the mean (s m)
standard deviation/ square root of the number of data points
what does increasing n mean in standard deviation of the mean?
increasing precision, the more measurements the more precise
what are the steps to performing a Q-test?
- take all data points and arrange them in increasing order
- only numbers from the lowest and highest should be considered to be discarded so determine the difference between the outlier and its closest neighbor
- divide this by the range
- if the calculated Q is larger than the selected q values it should be discarded
what is the purpose of a Q-test?
To determine the validity of an outlier point, only one point can be discarded
when is the Q test used?
with data sets between 3 and 10 measurements when one measurement appears to be an outlier
formula for density
m/v
1 mL =
1cm^3
oxidation means what?
oxidation means the loss of electrons
reduction means what?
reduction is the gain of electrons
if a substance has been oxidized what kind of agent is it?
it is the reducing agent
what is the oxidation number for an atom in its elemental form?
zero
what can be evidence of a chemical reaction in a solution?
color change, precipitate, deposition of substance onto a metal, gas formation
what is the net ionic equation?
an equation that only shows the atoms that directly participate in a reaction, it eliminates the bystander ions
how do you know if a reaction was endothermic?
a reaction is endothermic if the reaction feels cold, it is absorbing heat from its surroundings (so the change in enthalpy will be positive)
how do you know if a reaction was exothermic?
the reaction produced a warm feeling due to the release of heat
ideal gas law
Pv= nRT
How do you find the mean of a set of measurements?
x m = sum of all the values/ the number of values
how many significant figures does standard deviation have?
two, because it is calculated using absolute deviation
t-test for a comparison to an accepted value
l accepted value - mean of data points l> t* standard deviation of the mean
what degree of freedom should you use for a t-test comparison to an accepted value?
n-1
t-test for two independent measurements of the same quantity (with the same number of data points)
l mean of the data points for 1st set-mean of the data points for 2nd set l > t*(standard deviation of the mean 1st set^2 + standard deviation 2nd set^2)^1/2
what degrees of freedom should be used with a t-test with two independent measurements of the same quantity with the same number of data points?
2n-2
t-test for two independent measurements of the same quantity without the same number of data points
l mean of data points 1st set - mean of data points 2nd set l > ts12((n 1st set + n 2nd set)/n 1st setn 2nd set)^1/2
s 12 =
(((n 1st set -1)(standard deviation 1st set2)+(n 2nd set - 1)(standard deviation 2nd set^2)/(n 1st set + n 2nd set -2)) ^1/2
what degrees of freedom should be used with a t-test of two independent measurements with different numbers of data points?
n 1st set + n second set - 2
solution of known concentration
titrant
solution of unknown concentration
analyte
acid-base reaction
AB + CD —- AD +CB
why can the three reactions of acidic protons not be distinguished from each other?
Because they are all of similar strength
what do acids dissociate into?
H + Anions
what do bases dissociate into?
OH- + cation
estimate of the equivalence point
end point
M (molarity) =
moles/ volume
how many significant figures should be used in erlenmeyer flask measurments?
2 sig figs
(EX: 35 mL or 23 mL)
how many decimal places is a graduated cylinder reported to?
1 place
eg: .1
how many decimal places is a volumetric flask reported to?
2 places
eg: .01
how many decimal places are scale measurments recorded to?
3 places
eg: .001
charles law
V1/ T1 = V2/T2
boyles law
P1 *V1 = P2 *V2
avogadros law
P1/N1 = P2/N2
Gay-Lussacs law
P1/T1 = P2/T2
