AP Chem Practice AP questions

The complete photoelectron spectrum of an element is given. Which of the following electron configurations is consistent with the spectrum? A) 1s²2s²2p¹ B) 1s²2s²2p⁶3s²3p³ C) 1s²2s²2p⁶3s²3p⁶ D) 1s²2s²2p⁶3s²3p⁶4s²3d⁵

B) 1s²2s²2p⁶3s²3p³

the complete photoelectron spectrum of an element is given. Which of the following electron configurations is consistent with the spectrum? A) 1s²2s²2p¹ B) 1s²2s²2p⁶3s²3p³ C) 1s²2s²2p⁶3s²3p⁶ D) 1s²2s²2p⁶3s²3p⁶4s²3d⁵

B) 1s²2s²2p⁶3s²3p³

The photoelectron spectra for H and He are represented above. Which of the following statements best accounts for the fact that the peak on the He spectrum is farther left and higher than the peak on the H spectrum? A) He has an additional valence electron in a higher energy level than the valence electron in H B) He has a greater nuclear charge than H and an additional electron in the same energy level C) He has a completely filled valence shell in which the electrons are a greater distance from the nucleus than the distance between the H nucleus and its electrons D) It takes longer for the electrons in He to be removed due to the higher nuclear mass of He

B) He has a greater nuclear charge than H and an additional electron in the same energy level

Addition of Sulfuric acid (a weak acid) to barium hydroxide (a strong base) results in the formation of a precipitate. the net ionic equation for this reaction is: A) 2Hᐩ(aq) + 2OH⎺(aq) ↔ 2H₂O(l) B) H₂SO₃(aq) + Ba²ᐩ(aq) + 2OH⎺(aq) ↔ BaSO₃(s) + 2H₂O(l) C) 2Hᐩ(aq) + SO₃²⎺(aq) + Ba²ᐩ(aq) + 2OH⎺(aq) ↔ BaSO₃(s) + 2H₂O(l) D) H₂SO₃(aq) + Ba²ᐩ(aq) + 2OH⎺(aq) ↔ Ba²ᐩ(aq) + SO₃²⎺(aq) + 2H₂O(l) E) H₂SO₃(aq) + Ba(OH)₂(aq) ↔ BaSO₃(s) + 2H₂O(l)

B) H₂SO₃(aq) + Ba²ᐩ(aq) + 2OH⎺(aq) ↔ BaSO₃(s) + 2H₂O(l)

A sample containing atoms of C and F was analyzed using x-ray photoelectron spectroscopy. The portion of the spectrum showing the 1s peaks for atoms of the two elements is shown in the picture. Which of the following correctly identifies the 1s peak for the F atoms and provides an appropriate explanation? A) Peak X, because F has a smaller first ionization energy than C has B) Peak X, because F has a greater nuclear charge than C has C) Peak Y, Because F is more electronegative than C is D) Peak Y, because F has a smaller atomic radius than C has

B) Peak X, because F has a greater nuclear charge than C has

Which of the following is closest to the frequency of the light with photon energy of 3.3 x 10⁻¹⁹ J? A) 5.0 x 10⁻⁵³ s⁻¹ B) 5.0 x 10⁻¹⁶ s⁻¹ C) 5.0 x 10¹⁴ s⁻¹ D) 5.0 x 10⁵² s⁻¹

C) 5.0 x 10¹⁴ s⁻¹

Which of the following substances is a strong electrolyte when dissolved in water? A) sucrose B) Ethanol C) Sodium Nitrate D) Acetic acid E) Ammonia

C) Sodium Nitrate

A student uses visible spectrophotometry to determine the concentration of CoCl₂ (aq) in a sample solution. First the student prepares a set of CoCl₂ (aq) solutions of known concentration. Then the student uses a spectrophotometer to determine the absorbance of each of the standard solutions at a wavelength of 510 nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration. A wavelength of 510 nm corresponds to an approximate frequency of 6 x 10¹⁴ s⁻¹. What is the approximate energy of one photon of this light? A) 9 x 10⁴⁷ J B) 3 x 10¹⁷ J C) 5 x 10⁻⁷ J D) 4 x 10⁻¹⁹ J

D) 4 x 10⁻¹⁹ J

According to the compete photoelectron spectrum, which of the following is the identity of the element? A) Be B) C C) O D) Ne

D) Ne

the following balanced equation represents the decomposition of hydrogen peroxide: 2H₂O₂(aq) → 2H₂O(l) + O₂(g) The student claims that the reaction is and oxidation-reduction reaction. Which of the following statements correctly describes a change in oxidation number as the decomposition reaction proceeds? A) The oxidation number number of hydrogen changes from +2 to +1 B) The oxidation number number of hydrogen changes from +1 to +2 C) The oxidation number number of oxygen changes from -2 to -1 D) The oxidation number number of oxygen changes from -1 to 0

D) The oxidation number number of oxygen changes from -1 to 0

H₂Se(g) + 4O₂F(g) → SeF₆(g) + 2HF(g) + 4O₂(g) Which of the following is true regarding the reaction represented above? A)the oxidation number of O does not change B) The oxidation number of H changes from -1 to +1 C) The oxidation number of F changes from +1 to -1 D) The oxidation number of Se changes from -2 to +6 E) It is a disproportionation reaction for F

D) The oxidation number of Se changes from -2 to +6

Is a strong electrolyte in aqueous solution A) NH₃(g) B) H₃(g) C) H₂(g) D) H₂S(g) E) HBr(g)

E) HBr(g)

In which of the following species does sulfur have the same oxidation number as it does in H₂SO₄? A)H₂SO₃ B) S₂O₃²⁻ C) S²⁻ D) S₈ E) SO₂Cl₂

E) SO₂Cl₂

FRQ: Use the principles of atomic structure and/or chemical bonding to explain each of the following. In each part, your answers must include references to both substances. a. The atomic radius of Li is larger than that of Be. b. The second ionization energy of K is greater than the second ionization energy of Ca. c. The carbon-to-carbon bond energy in C2H4 is greater than it is in C2H6. d. The boiling point of Cl2 is lower than the boiling point of Br2

a. Both Li and Be have their outer electrons in the same shell (and/or they have the same number of inner core electrons shielding the valence electrons from the nucleus). However, Be has four protons and Li has only three protons. Therefore, the effective nuclear charge experienced (attraction experienced) by the valence (outer) electrons is greater in Be than in Li, so Be has a smaller atomic radius. b. The second electron removed from a potassium atom comes from the third level (inner core). The second electron removed from a calcium atom comes from the fourth level (valence level). The electrons in the third level are closer to the nucleus so the attraction is much greater than for electrons in the fourth level. c. C2H4 has a double bond between the two carbon atoms, whereas C2H6 has a carbon-carbon single bond. More energy is required to break a double bond in C2H4 than to break a single bond in C2H6; therefore, the carbon-to-carbon bond energy in C2H4 is greater. d. 1 point is earned for indicating that Cl2 and Br2 are both nonpolar and/or have only London dispersion forces (or van der Waals). 1 point for indicating that the more electrons, the more polarizable, the greater the dispersion forces, and the higher the boiling point.

FRQ) A compound containing the elements C, H, N, and O is analyzed. When a 1.2359 g sample is burned in excess oxygen, 2.241 g of CO₂ (g) is formed. the combustion analysis also showed that the sample contained 0.0648 g of H. i. Determine the mass, in grams, of C in the 1.2359 g sample of the compound. ii. When the compound is analyzed for N content only, the mass percent of N is found to be 28.84 percent. Determine the mass, in grams, of N in the original 1.2359 g sample of the compound. iii. Detirmine the mass, in grams, of O in the original 1.2359 g sample of the compound. iv. Determine the empirical formula of the compound.

i. 0.6116 g C ii. 0.3564 g N iii. 0.8147 g O iv. C₄N₂O₄H₅