Chem All Questions

Suppose that 7.06 mol of hydrogen gas occupies a 72.5 L steel tank. At what temperature in °C will the pressure in the tank be 803 torr? Enter your answer with one decimal place and no units.

-140.8

Calculate the energy change (ΔE) for the reaction below, N2(g) + 3 F2(g) → 2 NF3(g) given these bond energies of the reactants and products. Ν−N 163 kJ/mol N=N 418 kJ/mol Ν≡N 945 kJ/mol F −F 155 kJ/mol Ν−F 283 kJ/mol

-288 kJ

The local weather forecaster reports that the current barometric pressure is 31.0 inches of mercury. What is the current pressure in atmospheres? (1 in = 2.54 cm) Enter your answer with two decimal places and no units.

1.04

A line in the spectrum of atomic mercury has a wavelength of 255 nm. When mercury emits a photon of light at this wavelength, the frequency of this light is ___________ Hz. Answer in E-Notation with 3 significant figures.

1.18E15

A 1.0 mole sample of He is placed in an empty vessel to create a pressure of 0.5 atm. A 32 g quantity of CH4 is added to the vessel. The TOTAL pressure in the container will be _____________ atm.

1.5

What is the sum of the numbers of neutrons and electrons in the ion 118Sn1+?

117

A 22.8 g quantity of a liquid was vaporized completely in a piston-cylinder apparatus at 100oC against a constant pressure of 1.00 atm. During the process, 20.5 kJ of heat flowed into the system which did 5.48 kJ of work on the surroundings. What is the change in the internal energy of the liquid in kJ? Enter your answer with two decimal places. Do not include units with your answer. (1 L*atm = 101.3 J)

15.02

According to MO theory how many unpaired electrons are present in B2?

2

Consider the following unbalanced oxidation-reduction reaction: Fe2+ + Cl2 → Fe3+ + Cl- In the balanced equation, the number of electrons transferred is

2

Compute the approximate density (in g/L) of methane, CH4, at 18 °C and 3.65 atm. The molar mass of methane is 16.0. Enter your answer with two decimal places and no units.

2.44

Arrange the following in order of increasing boiling point. 1. CH3CH2OH 2. CH3CH2CH3 3. CH3-O-CH3 4. CH3CH2NH2 Enter your answer as #<#<#<#

2<3<4<1

The wavelength of one shade of green light is 520. nm. What is the energy of one photon of this light? Answer in E-Notation with 3 significant figures.

3.82E-19

Find ΔH (kJ) for C3H8 (g) + 6 H2O (g) → 3 CO2 (g) + 10 H2 C3H8 (g) + 3 H2O (g) → 3 CO (g) + 7 H2 (g) ΔH = 499 kJ CO (g) + H2O (g) → CO2 (g) + H2 (g) ΔH = -41 kJ Enter your answer as the nearest whole number without units.

376

Tetraphosphorus hexaoxide (м = 219.9 g/mol) is formed by the reaction of phosphorus with oxygen gas.P4(s) + 3O2(g) → P4O6(s)If a mixture of 75.3 g of phosphorus and 38.7 g of oxygen produce 43.3 g of P4O6, what is the percent yield for the reaction? Enter your answer with one decimal place and no units.

48.8

How many valence electrons are present in an atom of arsenic?

5

What is the molar mass of a hydrocarbon if 5.19E16 molecules of the hydrocarbon weigh 5.00 μg? Enter your answer with two sigfigs and no units.

58

How many grams of calcium chloride are needed to produce 10.0 g of potassium chloride according to the equation below? CaCl2(aq) + K2CO3(aq) → 2 KCl(aq) + CaCO3(aq) Enter your answer with two decimal places and no units.

7.44

In the reaction below, what volume of PCl5(g) will be produced by the reaction of 18.9 L of chlorine gas with excess phosphorus (P4) if all gas volumes are measured at STP? P4(g) + Cl2(g) => PCl5(g) (unbalanced) Enter your answer with two decimal places and no units.

7.56

How many unit cells share an atom which is located at a corner (or lattice point) of a unit cell?

8

Suppose the element A contains three isotopes, 86A (atomic mass 85.909 amu, abundance 48.596%) 87A (atomic mass 86.908 amu, abundance 7.00%) and 88A (atomic mass 87.906 amu). What would be the atomic mass of A that would appear in the periodic table? Enter your answer in decimal format with three decimal places and no units.

86.866

With increasing value of the quantum number l, subshells are named s, p, d, f, g, h, i, etc. How many g orbitals are allowed in a g subshell? Enter your answer as a whole number without units.

9

For a hydrogen atom, which electronic transition would result in the emission of a photon with the highest energy? A. 4p to 2s B. 2s to 3p C. 5f to 3d D. 3p to 6d

A. 4p to 2s

Which of the following molecules or ions will have a Lewis structure most like that of phosphorus trichloride, PCl 3? A. ClO3 - B. Cl2CO C. CO3 2- D. BF3 E. SO3

A. ClO3 -

Which liberates the most energy? A. Li(g) + e- → Li-(g) B. K(g) + e- → K-(g) C. Na(g) + e- → Na-(g) D. Rb(g) + e- → Rb-(g)

A. Li(g) + e- → Li-(g)

Consider the following electron configurations for neutral atoms: Atom 1 = 1s2 2s2 2p6 3s2 Atom 2 = 1s2 2s2 2p6 3s2 3p4 Atom 3 = 1s2 2s2 2p6 3s2 3p6 Which atom would be expected to have the largest third ionization energy?

Atom 1

What would be the molarity of a solution obtained by diluting 125 mL of 6.00 M HCl to 500. mL? A. 1.25 B. 1.50 C. 0.667 D. 24.0 E. 10.4

B. 1.50

Aqueous solutions of barium chloride and silver nitrate are mixed to form solid silver chloride and aqueous barium nitrate. The balanced molecular equation contains which one of the following terms? A. AgCl (s) B. 2AgCl (s) C. 3AgCl (aq) D. BaNO3 (aq) E. 2Ba(NO3)2 (aq)

B. 2AgCl (s)

Which has the largest atomic size: A. Br B. Br- C. Br+

B. Br-

Which of these is least characteristic of metals? A. Moderately high melting point B. Brittleness C. Malleability D. Good thermal conductivity E. Good electrical conductivity

B. Brittleness

A 46.0 g sample of a metal is heated to 95.0°C and then placed in a calorimeter containing 120.0 g of water (c = 4.18 J/g°C) at 21.6°C. The final temperature of the water is 24.5°C. Which metal was used? A. Aluminum (c = 0.89 J/g°C) B. Iron (c = 0.45 J/g°C) C. Copper (c = 0.20 J/g°C) D. Lead (c = 0.14 J/g°C) E. none of these

B. Iron (c = 0.45 J/g°C)

Which of the following substances is an example of a strong electrolyte? A. C6H12O6 B. KNO3 C. Ag2SO4 D. C4H10

B. KNO3

Energy states of atoms containing more than one electron are influenced by nucleus-electron and electron-electron interactions. Which of the following statements correctly describes these effects? A. Larger nuclear charge lowers energy, more electrons in an orbital lowers energy B. Larger nuclear charge lowers energy, more electrons in an orbital increases energy C. Smaller nuclear charge lowers energy, more electrons in an orbital lowers energy D. Smaller nuclear charge lowers energy, more electrons in an orbital increases energy E. None of the above statements is generally correct

B. Larger nuclear charge lowers energy, more electrons in an orbital increases energy

When an exothermic reaction is carried out in a coffee-cup calorimeter, what statement is correct? A. The q of H2O is negative. B. The enthalpy of the products is lower than that of the reactants. C. The temperature of the water decreases. D. The enthalpy change for the reaction is positive. E. The reaction absorbs heat from the water.

B. The enthalpy of the products is lower than that of the reactants.

Which of the following statements is true for energy level differences seen when comparing the s, p, d, and f subshells in the hydrogen atom for a given value of n? A. There are different values of quantum number l for each orbital which cause differences in energy. B. There are no differences in energy between the s, p, d, and f orbitals. C. There are different values of quantum number l for each orbital which cause differences in energy. D. There are different values of quantum number m s for each orbital which cause differences in energy.

B. There are no differences in energy between the s, p, d, and f orbitals.

What is the oxidation number of chromium in Cr2O72-? A. +8 B. +7 C. +6 D. +5

C. +6

A compound is found to form between As and Br. What is the most likely formula for this compound? A. As3Br B. As2Br C. AsBr3 D. AsBr E. As2Br3

C. AsBr3

Give formula for the following compound: chlorine trifluoride

ClF3

Match the element below's symbol and group number with its Z value. Enter only the letter of the correct choice. K; 1A (1) [a] A. Z = 33 B. Z = 20 C. Z = 35 D. Z = 19 E. Z = 12

D

When 2.61 g of solid Na2CO3 is dissolved in sufficient water to make 250. mL of solution, the concentration of sodium ion is: A. 0.0246 M B. 10.4 M C. 0.205 M D. 0.197 M E. 0.141 M

D. 0.197 M

Predict the approximate bond angles in SF3+ using the VSEPR theory. A. more than 120 B. exactly 120 C. between 109 and 120 D. between 90 and 109 E. less than 90

D. between 90 and 109

The statement "The total mass of materials is not affected by a chemical change in those materials" is called a(n) __________. A. observation B. experiment C. theory D. natural law

D. natural law

One of the main advantages of Hydrogen as a fuel is that: A. plants can economically produce the hydrogen needed B. it exists as a free gas C. it can be economically supplied by the world's ocean D. the only product of hydrogen combustion is water E. it contains a large amount of energy per unit volume of hydrogen gas

D. the only product of hydrogen combustion is water

Select the gas with the highest average kinetic energy per mole at 298 K. A. O2 B. CO2 C. H2O D. H2 E. All have the same average kinetic energy.

E. All have the same average kinetic

The internal energy of a system changes only when heat is gained or lost by the system. (T/F)

F

Which set of these molecules have ONLY polar covalent bonds? NO2, PCl3, N2, H2O, P4, NH3

NO2, PCl3, H2O, NH3

Give formula for the following compound: tetraphosphorus heptasulfide

P4S7

A compound composed of sulfur and fluorine is found to contain 25.24% by mass of sulfur. If the molar mass of the compound is 254.11 g/mol, what is its molecular formula?

S2F10

Dilithium crystals are the fuel of the starship Enterprise (of Star Trek fame). Based on molecular orbital theory, is this compound predicted to be stable (and if so, what is the bond order)?

Stable, 1 bond order

When a system performs work on the surroundings, the work is reported with a negative sign. (T/F)

T

Atoms with greatly different electronegativity values are expected to form

ionic bonds

Which orbital hybridization is associated with a tetrahedral electron group arrangement?

sp3