Bonding, Molecules, Lab



Bonding, Molecules, Lab

Questions 1-3 refer to the following diatomic species.

(A) Li2 (B) B2 (C) N2

(D) O2 (E) F2

_____1. Has the largest bond–dissociation energy

_____2. Has a bond order of 2

_____3. Contains 1 sigma( σ )and 2 pi (π) bonds

_____4. In a molecule in which the central atom exhibits sp3d2 hybrid orbitals, the electron pairs are directed toward the corners of

(A) tetrahedron (B) square based pyramid (C) trigonal pyramid

(D) square (E) octahedron

_____5. CH3CH2OH boils at 78C and CH3OCH3 boils at –24C, although both compounds have the same composition. This difference in boiling points may be attributed to a difference in

(A) molecular mass (B) density

(C) specific heat (D) hydrogen bonding

(E) heat of combustion

_____6. X. CH3–CH2–CH2–CH2–CH3

Y. CH3–CH2–CH2–CH2–OH

Z. HO–CH2–CH2–CH2–OH

Based on concepts of polarity and hydrogen bonding, which of the following sequences correctly lists the compounds above in the order of their increasing solubility in water?

(A) Z < Y < X (B) Y < Z < X

(C) Y < X < Z (D) X < Z < Y

(E) X < Y < Z

_____7. Concentrations of colored substances are commonly measured by means of a spectrophotometer. Which of the following would ensure that correct values are obtained for the measured absorbance?

I. There must be enough sample in the tube to cover the entire light path.

II The instrument must be periodically reset using a standard.

III The solution must be saturated.

(A) I only (B) II only

(C) I and II only (D) II and III only

(E) I, II, and III

_____8 A strip of metallic scandium, Sc, is placed in a beaker containing 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 which of the following statements?

(A) Nitric acid is a strong acid

(B) In a solution scandium nitrate is yellow and scandium chloride is colorless

(C) Nitric acid reacts with metals to form hydrogen

(D) Scandium reacts with nitric acid to form a brown gas

(E) Scandium and nitric acid react in mole proportions of 1 to 3

_____9. The electron–dot structure (Lewis structure) for which of the following molecules would have two unshared pairs of electrons on the central atom?

(A) H2S (B) NH3 (C) CH4

(D) HCN (E) CO2

_____10 Correct procedures for a titration include which of the following?

I. Draining a pipet by touching the tip to the side of the container used for the titration

II. Rinsing the buret with distilled water just before filling it with the liquid to be titrated

III. Swirling the solution frequently during the titration

(A) I only (B) II only

(C)I and III only (D) II and III only

(E) I, II, and III

_____11. To determine the molar mass of a solid monoprotic acid, a student titrated a weighed sample of the acid with standardized aqueous NaOH. Which of the following could explain why the student obtained a molar mass that was too large?

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

II. Addition of more water than was needed to dissolve the acid

III. Addition of some base beyond the equivalence point

(A) I only (B) III only

(C) I and II only (D) II and III only

(E) I, II, and III

Questions 12-15 refer to the following descriptions of bonding in different types of solids.

(A) Lattice of positive and negative ions held together by electrostatic forces

(B) Closely packed lattice with delocalized electrons throughout

(C) Strong single covalent bonds with weak intermolecular forces

(D) Strong multiple covalent bonds (including _-bonds) with weak intermolecular forces

(A) Lattice of positive and negative ions held together by electrostatic forces

(B) Closely packed lattice with delocalized electrons throughout

(C) Strong single covalent bonds with weak intermolecular forces

(D) Strong multiple covalent bonds (includingπ-bonds) with weak intermolecular forces

(E) Macromolecules held together with strong polar bonds

_____12. Cesium chloride, CsCl(s)

_____13. Gold, Au(s)

_____14. Carbon dioxide, CO2(s)

_____15. Methane, CH4(s

_____16. When a solution of sodium chloride is vaporized in a flame, the color of the flame is

(A) blue (B) yellow (C) green

(D) violet (E) white

_____17. The safest and most effective emergency procedure to treat an acid splash on skin is to do which of the following immediately?

(A) Dry the affected area with paper towels

(B) Sprinkle the affected area with powdered Na2SO4(s)

(C) Flush the affected area with water and then with a dilute NaOH solution

(D) Flush the affected area with water and then with a dilute NaHCO3 solution

(E) Flush the affected area with water and then with a dilute vinegar solution

_____18 Appropriate uses of a visible-light spectrophotometer include which of the following?

I. Determining the concentration of a solution of Cu(NO3)2

II. Measuring the conductivity of a solution of KMnO4

III. Determining which ions are present in a solution that may contain Na+, Mg2+, Al3+

(A) I only (B) II only

(C) III only (D) I and II only

(E) I and III only

_____19. The melting point of MgO is higher than that of NaF. Explanations for this observation include which of the following?

I. Mg2+ is more positively charged than Na+.

II. O2– is more negatively charged than F–.

III. The O2– ion is smaller than the F– ion.

(A) II only (B) I and II only

(C) I and III only (D) II and III only

(E) I, II, and III

_____20. Types of hybridization exhibited by the C atoms in propene, CH3CHCH2, include which of the following?

I. sp II. sp2 III. sp3

(A) I only (B) III only

(C) I and II only (D) II and III only

(E) I, II, and III

_____21 A sample of 61.8 g of H3BO3, a weak acid, is dissolved in 1,000 g of water to make a 1.0-molal solution. Which of the following would be the best procedure to determine the molarity of the solution? (Assume no additional information is available.)

(A) Titration of the solution with standard acid

(B) Measurement of the pH with a pH meter

(C) Determination of the boiling point of the solution

(D) Measurement of the total volume of the solution

(E) Measurement of the specific heat of the solution

_____22 Of the following molecules, which has the largest dipole moment?

(A) CO (B) CO2 (C) O2

(D) HF (E) F2

_____23. After completing an experiment to determine gravimetrically the percentage of water in a hydrate, a student reported a value of 38 percent. The correct value for the percentage of water in the hydrate is 51 percent. Which of the following is the most likely explanation for this difference?

(A) Strong initial heating caused some of the hydrate sample to spatter out of the crucible.

(B) The dehydrated sample absorbed moisture after heating

(C) The amount of the hydrate sample used was too small.

(D) The crucible was not heated to constant mass before use

(E) Excess heating caused the dehydrated sample to decompose.

_____24 Which of the following gases deviates most from ideal behavior?

(A) SO2 (B) Ne (C) CH4

(D) N2 (E) H2

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