AP Chem 1994 MC

A direct current power supply of low voltage(less than 10 volts) has lost the markings that indicate which output terminal is positive and which is negative. A chemist suggests that the power supply terminals be connected to a pair of platinum electrodes that dip into 0.1 molar KI solution. What identifies the polarities of the power supply terminals?

A gas will be evolved only at the negative electrode.

Is added to silicon to enhance its properties as a semiconductor

As

A hydrocarbon gas with an empirical formula CH2 has a density of 1.88 grams per L at 0C and 1 atm. A possible formula for the hydrocarbon is...

C3H6

Hund's Rule

Can be used to predict that a gaseous carbon atom in its ground state is paramagnetic

When an aqueous solution of NaOH is added to an aqueous solution of potassium dichromate, K2Cr2O7, the dichromate ion is converted to...

CrO4 (2-)

PCl3(g)+Cl2(g)->PCl5(g)+E Some PCl3 and Cl2 are mixed in a container at 200C and the system reaches equilibrium according to the equation. What causes an increase in the number of moles of PCl5 present at equilibrium?

Decreasing the volume of the container

What are the correct procedures for a titration?

Draining a pipet by touching the tip to the side of the container used for titration and swirling the solution frequently during the titration.

Wave Nature of Matter

Explains the experimental phenomenon of electron diffraction

To determine the molar mass of a solid monoprotic acid, a student titrated a weighed sample of the acid with standardized aqueous NaOH. What could explain why the student obtained a molar mass that was too large?

Failure to rinse all acid from the weighing paper into the titration vessel.

What is lower for a 1.0 molar aqueous solution than pure water?

Freezing point

Spontaneous at 298K and non-spontaneous at high temps

G S and H are negative

Bases HSO4-+H2O->H3O++SO42-

H2O and SO42-

CH3CH2OH boils at 78C and CH3OCH3 boils at 24C, although both compounds have the same composition. This difference is due to...

Hydrogen bonding

Molecules that have planar configurations include.... I. BCl3 II. CHCl3 III. NCl3

I only

For which of the following processes would S have a negative value? I. 2Fe2O3(s)->4Fe(s)+3O2(g) II. Mg(2+)+2OH(-)->Mg(OH)2(s) III. H2(g)+C2H4(g)->C2H6(g)

II and III

Pauli Exclusion Principle

Indicates that an atomic orbital can hold no more than two electrons

What would be likely to change the boiling point of a sample of a pure liquid in an open container?

Moving the container and liquid to s higher altitude

Quantum Numbers for gallium

N=4 L=1 Ml=1 Ms=0.5

Oxidizing agent

One being reduced

Utilized as a shield from sources of radiation

Pb

Heisenberg uncertainty principle

Predicts that it is impossible to determine simultaneously the exact position and the exact velocity of an electron

A strip of metallic scandium, Sc, is placed in a beaker contains concentrated nitric acid. A brown gas rapidly forms, the scandium disappears, and the resulting liquid is brown-yellow but becomes colorless when warmed. These observations best support that...

Sc reacts with nitric acid to form a brown gas

Relatively slow rates of chemical reaction are associated with...

Strong bonds in reaction molecules

Zn(s)+Cu(2+)->Zn(2+)+Cu(s) An electrolytic cell based on the reaction represented above was constructed from zinc and copper half cells. The observed voltage was found to be 1.00 volt instead of the standard cell potential, E, of 1.10 volts. What could account for this observation?

The Zn(2+) solution was mor concentrated than the Cu(2+) solution.

Given that a solution is 5% sucrose by mass, what additional information is necessary to calculate the molarity of the solution?

The density of the solution and the molar mass of sucrose

A solution of calcium hypochlorite, a common additive to swimming pool water is basic because

The hydrolysis of the OCl- ion

Concentrations of colored substances are commonly measured by means of a spectrophotometer. What would ensure that correct values are obtained for the measured absorbance?

There must be enough sample in the tube to cover the entire light path and the instrument must be periodically reset using a standard.

Alpha particles

They are helium nuclei that have a mass number of 4 and a charge of 2+

Utilized as a coating to protect Fe from corrosion

Zn

What solid dissolves in water to form a colorless solution?

ZnCl2

The nuclide a(249, 96)Cm is radioactive and decays by the loss of one beta (i-) particle. The product nuclide is...

a(249, 97)Bk

Substances X and Y that were in a solution were separated in the laboratory using the technique of fractional crystallization. This fractional crystallization is possible because substances X and Y have different...

solubilities

Hybrid orbital for a octahedron

sp3d2