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