chem 2 lab final

How many valence electrons are in KrF2?

22

Which of the following count as one electron domain?

4 electrons in a double bond, pair of electrons in a single bond, lone pair of electrons

The absorbance of which of the following is going to be measured with the spectrophotometer.

FeNCS2+

what is used to find Ka when all but one concentration is given in the problem?

Ice table

Non-spontaneous reactions are reactions that do not automatically produce any product. How can products be made to form from a non-spontaneous reaction?

Products cannot be made to form from a non-spontaneous reaction.

Suppose the pinch clamp on the flask assembly was not opened prior to heating the flask assembly in boiling water. Which of the following is the most likely problem that this would create?

The stopper assembly might be forced out of the mouth of the flask

in the determination of aspirin in aspirin tablets lab a curvette is

a sample holder for measuring absorbance

what is an unfavorable resonance structure?

a structure that gives too many electrons to an element

The larger the "load" connected to the hand-held device, the larger the amount of work the device must do. How does one assess how large the load is in this lab?

by how hard the hand is too turn

uppose a chemical reaction is initially at equilibrium, but then a change is made in the equilibrium system. To return to equilibrium, the equilibrium position will shift so as to

counteract the change

What is the name of the hand-held device used to produce electricity In this lab?

dc generator

A blank is a solution that should contain

everything the sample contains except for the species being measured

The electronic geometry gives the "actual" shape of a molecule. true or false

false

The volume occupied by air inside the flask is equal to the volume engraved on the flask true or false

false

In the Dumas method lab the volume of the Erlenmeyer flask is measured by

filling the flask with water, weighing it, and converting the mass of added water to volume using density.

before using the volumetric flask in the equilibrium constant using spectrophy lab what must you do?

it must be swirled and inverted before use

According to Beer's law, a plot of absorbance vs. concentration is

linear

The Dumas method is used to determine the what of a volatile liquid?

molar mass

if a resonance structure is symmetrical is it likely to be?

non polar

Acetic acid is a weak acid. Suppose 1 mole of acetic acid is placed in 1 L of water. In this solution dissociation of the acetic acid occurs at

only a small extent

if a resonance structure is not symmetrical it is likely to be?

polar

According to Le Chatelier's principle, adding heat to a system is equivalent to

raising the temperature

An indication that vaporization of the unknown liquid is complete is that the

ring of liquid around the boiling stone disappears or stops changing.

A beaker contains the following equilibrium system (as before): 2CrO42-(aq, yellow) + 2H+(aq) ⇌ Cr2O72-(aq, orange) + H2O(l) If solid Na2CrO4 is added to the solution, the equilibrium will

shift to the right

In this lab, when the NaSCN concentration is increased, the equilibrium constant

stays the same

The cooling curve for pure nitrobenzene is shown below. Regarding supercooling, this curve shows

super cooling at the dip

The electronic geometry of PCl3 is

tetrahedral

When the dissociation constant of a weak acid occurs, Ka, is calculated for this lab, which one of the following is used to calculate Ka?

the equilibrium concentration of the weak acid

You can tell a pure solvent has reached its freezing point on the graph when?

the line levels out past the supercooling point

In this experiment, 0.1 M HNO3 is used to dilute all the solutions because

the solution must be kept acidic to prevent Fe3+ from precipitating.

which row of the ice table is used to calculate Ka?

third row

The molecular geometry of PCl3 is

trigonal pyramidal

Electrical work is done by turning the crank of the hand-held device. true or false

true

In the equilibrium constant using spectrophy lab a volumetric flask without a stopper is ?

useless

formal charge formula

valence electrons - dots - lines

Which instrument is used to measure the amount of voltage produced from the reaction between a metal and an ionic compound?

voltmeter

In this lab the inside of the flask must be absolutely dry before it is fitted with the stopper assembly and weighed. The main reason is that

when the water inside the flask vaporizes, it will displace the air in the flask during heating. Then, when cooled down, the water will condense, and too much water will be sucked into the flask.