Chem 101 test 3

Ideal Gas Law V'N

the ideal law with all factors at STP, including # of moles (v1/v2)=(n1/n2) or PV=nRT

n=g/M

(P+an/v2)(V-nh)=nRT

V'1/p

(v1/v2)=(p2/p1)

V'T

(v1/v2)=(t1/t2)

Which of the following statements are true?

*There are gas molecules that move slower than the average *The average kinetic energy of gas molecules decreases with decreasing temperature. *All the gas molecules in a sample cannot have the same kinetic energy. *The average speed of gas molecules decreases with decreasing temperature

What is the only possible value of mℓ for an electron in an s orbital?

0 Since the allowed values for mℓ range from −ℓ to +ℓ, once you know the value for ℓ you know the values for mℓ.

Charles' Law

direct relationship between volume and temperature V1/T1 = V2/T2

Aufbau Principle

1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s

Give the complete ground-state electron configuration for silicon (Si).

1s^2 2s^2 2p^6 3s^2 3p^2 using ground-state electron [Ne]3s^23p^2

copper (Cu) using noble-gas shorthand.

1s^22s^22p^63s^23p^64s^13d^10 [Ar]4s^13d^10

Si

3p↑↑ 3s⇌ 2p⇌⇌⇌ 2s⇌ 1s⇌ [Ne] 3s²3p²

Valence electrons in Pb

4

Valance in N

5

Planck's constant

6.624x10⁻²⁴

Valence electrons in Br

7

Determine the percent yield for the reaction. 2Mg(s)+O2(g)→2MgO(s) When 10.1g Mg is allowed to react with 10.4g O2, 12.0g MgO is collected.

71.7% The percent yield is the actual yield divided by the theoretical yield times 100%. Percent yield should always be less than 100

A student tests four solids for their ability to complete an electrical circuit when dissolved in water by observing their ability to close a circuit containing a light bulb and obtains the following results: Solid Concentration (M) Strength of light emitted A 0.20 Bright B 0.20 Dim C 0.20 None D 0.20 Bright Which of the solids is a weak electrolyte when dissolved in water?

B Molecular compounds that are weak acids or weak bases are weak electrolytes. They dissociate into component ions incompletely in water. For example, ammonia is a weak electrolyte.

The constant motion of gas molecules causes diffusion and effusion.

Diffusion is the gradual mixing of two substances resulting from the movement of their particles. Effusion is the gradual escape of gas molecules through microscopic holes in their container.

A quantity of CO gas occupies a volume of 0.42L at 2.0atm and 329K . The pressure of the gas is lowered and its temperature is raised until its volume is 5.0L

Find the density of the CO under the new conditions. d = 0.17 gL

The binding energy of electrons in a metal is 176kJ/mol

Find the threshold frequency of the metal. ν =4.41×1014 s^−1

A flask at room temperature contains exactly equal amounts (in moles) of nitrogen and xenon. Sort the conditions based on the gas described. Nitrogen has the greater value

Gas for which the molecules or atoms have the greatest average velocity Gas that would have a higher rate of effusion through a small hole opened in the flask

A laser pulse with wavelength 535nm contains 4.85mJ of energy.

How many photons are in the laser pulse? N =1.31×1016

Rank the following elements in order of decreasing atomic radius.

I Br Cl F

The limiting reactant is the ĵreactant that can form the least amount of product. The given mass of Mg will form less MgO than the given mass of O2.

Mg(s)

Which statements about a sample of gas containing molecules of different masses are true?

More-massive gas molecules in the sample have lower rms speed than less-massive ones The average kinetic energy depends only on the temperature. However, a heavier molecule will move more slowly than a lighter molecule if both have the same kinetic energy.

The student is now told that the four solids, in no particular order, are aluminum chloride (AlCl3), sugar (C6H12O6), acetic acid (CH3COOH), and sodium bromide (NaBr). Assuming that conductivity is correlated to the number of ions in solution, rank the four substances based on how well a 0.20 M solution in water will conduct electricity.

Most Conductive to Least conductive Aluminum chloride sodium bromide acetic acid sugar

Iron(II) sulfide reacts with hydrochloric acid according to the reaction: FeS(s)+2HCl(aq)→FeCl2(s)+H2S(g) A reaction mixture initially contains 0.248mol FeS and 0.646mol HCl.

Once the reaction has occurred as completely as possible, what amount (in moles) of the excess reactant is left? n = 0.150 mol

It is important to realize that not all molecules in a sample will have the same kinetic energy

The speed of a particle with average kinetic energy is called the root mean square (rms) speed, vrms.

The Kinetic Molecular Theory of Gases

To understand how gas molecules behave in terms of motion, speed, and energy. relationship between temperature and the average speed Increasing the temperature of a gas sample increases the average kinetic energy (speed) of the molecules.

Find the volume of 0.100M hydrochloric acid necessary to react completely with 1.53g Al(OH)3

V = 0.588L

Combined Gas Formula

a law combines Lussac's, Charles's, and Boyles's Law, indirect P1V1/T1=P2V2/T2

isoelectronic

atoms have the same number of electrons ex. O²⁻ and Na⁺=10e

Elements with 5 or more valence electrons tend to

gain electrons

Both gases have the same value

gas for which the molecules or atoms have the greatest average kinetic energy Gas that exerts the greater partial pressure

Elements with 3 or fewer valence electrons tend to

lose

Give a combination of four quantum numbers that could be assigned to an electron occupying a 5p orbital.

n, l, ml, ms = 5,1,0,0.5

Delta E=

E2-E1=hZ=hc/λ

Rank the following elements in order of largest to smallest

P S Cl Ar

Paramagnetic substances contain

one or more unpaired electrons and are attracted to a magnetic field

The frequency of a light emission is proportional

to the energy difference between two levels. Therefore, the frequency of the light would be greater

Before using the de Broglie relation

λ = h/mv, the mass of the bullet needed to be converted to kilograms using the conversion factor 1000 g = 1 kg. Since the units for Planck's constant are kg⋅m2/s, this will allow the mass of the bullet to properly cancel during the calculation.

he shielding of electrons gives rise to an effective nuclear charge, Zeff, which explains why boron is larger than oxygen. Estimate the approximate Zeff felt by a valence electron of boron and oxygen, respectively?

+3 and +6

What are the possible values of mℓ for an electron in a d orbital?

-2,-1,0,1,2 Since the allowed values for mℓ range from −ℓ to +ℓ, once you know the value for ℓ you know the values for mℓ.

O

2p⇌ ↑ ↑ 2s⇌ 1s⇌ [He] 2s² 2p⁴

Ne

2p⇌⇌⇌ 2s⇌ 1s⇌ [He] 2s²2p⁶

Valence electrons in Al

3

According to the quantum-mechanical model for the hydrogen atom, which of the following transitions would produce light with the longer wavelength: 3p→2s or 4p→3p?

4p→3p

Which of the following set of quantum numbers (ordered n, ℓ, mℓ, ms) are possible for an electron in an atom?

5, 3, -3, 1/2 5, 3, 0, 1/2 3, 2, 2, -1/2

λ Z/s⁻¹

=C 3x 10² m/s

Solid Concentration (M) Strength of light emitted A 0.20 Bright B 0.20 Dim C 0.20 None D 0.20 Bright The student is told that one of the four solids tested is actually aluminum chloride,AlCl3. Which of the solids could be AlCl3?

A and D All ionic substances and strong acids are strong electrolytes.

A 0.22-caliber handgun fires a 29-g bullet at a velocity of 775 m/s.

Calculate the de Broglie wavelength of the bullet. λ = 2.9×10−35m Is the wave nature of matter significant for bullets?-NO Although quantum mechanics applies to all objects, most everyday objects are too large to exhibit any noticeable wavecharacteristics.

To what volume should you dilute 25mL of a 11M H2SO4 solution to obtain a 0.17M H2SO4 solution?

Dilutions are a core technique for any chemist, and the following equation, which is represented in two different ways, can be used to relate the molarity and volume of the original solution to the molarity and volume of the diluted solution: V=1.6L M1V1=M2V2 MconcVconc=MdilVdil In the second representation of the equation, "conc" and "dil" represent "concentrated" and "diluted."

Diffusion

Hairspray in the bedroom can be smelled in the hallway

conducts electricity

NaCl solution

The allowed values for mℓ range from −ℓ to +ℓ and the allowed values for ℓ are integers between zero and n−1.

Once you know the value for n, you can determine the acceptable ℓ values, and from there the acceptable mℓ values. The ms values are fixed at either 1/2 or −1/2.

Here is a more complex redox reaction involving the dichromate ion in acidic solution: 3S2− + 14H+ + Cr2O72− → 3S +2Cr3+ + 7H2O Classify each reactant as the reducing agent, oxidizing agent, or neither.

Oxidizing agent: Cr2O7^2- Reducing agent:S2- Neither:H+

For the given reactions, classify the reactants as the reducing agent, oxidizing agent, or neither. 3O2 + 4Fe → 2Fe2O3 H2 + Br2 → 2HBr

Oxidizing agents- O2 and Br2 Reducing agents- H2 and Fe

Determine the theoretical yield for the reaction. 2Mg(s)+O2(g)→2MgO(s) When 10.1g Mg is allowed to react with 10.4g O2, 12.0g MgO is collected.

The theoretical yield is determined from the limiting reactant. The mass of Mg must be converted to moles of Mg to moles of MgO to grams of MgO. m = 16.7g

Compare the volume of 22.1g of helium to 22.1g of argon gas (under identical conditions). term-0

The volume would be greater for helium gas. Helium has a lower atomic mass than argon. The same mass of helium gas would contain a greater number of moles and have a larger volume.

A weather balloon is inflated to a volume of 29.7L at a pressure of 735mmHg and a temperature of 25.9∘C. The balloon rises in the atmosphere to an altitude where the pressure is 375mmHg and the temperature is -14.6∘C. Assuming the balloon can freely expand, calculate the volume of the balloon at this altitude

V balloon =50.3L The number of moles in the weather balloon will remain constant. According to the ideal gas law, the changes in pressure and temperature will cause a change in volume. Volume and pressure are inversely related, while volume and temperature are directly related

What is the volume occupied by 22.1g of argon gas at a pressure of 1.38atm and a temperature of 308K ?

V=10.1 L The ideal gas law is used to determine the volume of argon gas. The mass should first be converted to moles by dividing by the atomic mass.

A 1.00 L flask is filled with 1.20g of argon at 25 ∘C. A sample of ethane vapor is added to the same flask until the total pressure is 1.350atm .

What is the partial pressure of argon, PAr, in the flask? PAr = 0.735 atm Before ethane was added, the percent by volume of argon in the flask was 100% and the partial pressure of argon was equivalent to the total pressure of the flask. The total volume of the flask, the temperature of the flask, and the amount of argon remain constant after ethane was added; therefore the partial pressure of argon is the same before and after ethane was added. The total pressure of the flask is now equal to the combined partial pressures of both argon and ethane.

A 1.00 L flask is filled with 1.20g of argon at 25 ∘C. A sample of ethane vapor is added to the same flask until the total pressure is 1.350atm .

What is the partial pressure of ethane, Pethane, in the flask? Pethane = 0.615 atm Dalton's law of partial pressures states that the total pressure of a system is equal to the sum of the partial pressures of the component gases in the mixture. The expression for Dalton's law of partial pressure is Ptotal=PA+PB+... The partial pressure of an individual gas can be used in stoichiometric calculations involving chemical reactions.

An electron has an uncertainty in its position of 499pm

What is the uncertainty in its velocity? Δv =1.16×105 ms

An electron in a hydrogen atom relaxes to the n=4 level, emitting light of 114 THz.

What is the value of n for the level in which the electron originated? n =6

A 9.00mL ampule of a 0.140M solution of naphthalene in hexane is excited with a flash of light. The naphthalene emits 19.0J of energy at an average wavelength of 349 nm

What percentage of the naphthalene molecules emitted a photon? percentage =4.40 %

Consider the following precipitation reaction: 2Na3PO4(aq)+3CuCl2(aq)→ Cu3(PO4)2(s)+6NaCl(aq)

What volume of 0.183M Na3PO4 solution is necessary to completely react with 93.7mL of 0.117M CuCl2? V =39.9 mL

Oxygen gas reacts with powdered aluminum according to the following reaction: 4Al(s)+3O2(g)→2Al2O3(s)

What volume of O2 gas (in L), measured at 765mmHg and 19∘C, is required to completely react with 50.0g of Al? V = 33.1L

Effusion

When a hole is made in the top of a coke bottle dioxide gas moves out of the bottle over time OR a leak in a gas cylinder causes the volume to decrease

The magnetic quantum number mℓ

corresponds to the orbital in which the electron is located. Instead of 2px, 2py, and 2pz, the three 2p orbitals can be labeled −1, 0, and 1, but not necessarily respectively. As a rule, mℓ can have integer values ranging from −ℓ to +ℓ

The principal quantum number n

corresponds to the shell in which the electron is located. Thus n can therefore be any integer. For example, an electron in the 2p subshell has a principal quantum number of n=2 because 2p is in the second shell.

spin quantum number ms

corresponds to the spin of the electron in the orbital. A value of 1/2 means an "up" spin, whereas −1/2 means a "down" spin.

azimuthal or angular momentum quantum number ℓ

corresponds to the subshell in which the electron is located. s subshells are coded as 0, p subshells as 1, d as 2, and f as 3. For example, an electron in the 2p subshell has ℓ=1. As a rule, ℓ can have integer values ranging from 0 to n−1.

Pauli Exclusion Principle

fill in singly before pairing px py pz

Avogadro's Law

he direct relationship between the # of moles and volume V1/n1= V2/n2

One mole of nitrogen and one mole of neon are combined in a closed container at STP.

how big is the container? V = 44.8L

Boyle's law

indirect relationship between pressure and volume P1 x V1 = P2 x V2

Volume is

inversely proportional to pressure Directly proportional to temperature and # of mols

Do the same for an electron occupying a 6d orbital.

n, l, ml, ms = 6,2,-2,-0.5

Diamagnetic substances contain

no net electron spin and are repelled from a magnetic field

Which elements do you expect to lose electrons in their chemical reactions? Which do you expect to gain electrons?

tend to lose electrons- Al and Pb tend to gain electrons- Br and N

Gay-Lussac's Law

the direct relationship between pressure and temperature P1/T1 = P2/T2

Valence electrons are

the total number of electrons in the outermost shell. Knowing how many valence electrons are in elements is helpful in deciding whether elements will lose or gain electrons in a reaction. In this case, Al contains 3 valence electrons

The rms speed may be expressed by the following equation:

vrms=√3RT/M R= ideal gas constant T=absolute temperature M=molar mass of the substance in kilograms per mole.