CHEM MIDTERM

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1. What is an atom?

A. A particle with only protons.

B. A nucleus surrounded by neutrons.

C. The smallest unit of energy.

D. The smallest unit of matter that maintains its chemical identity.

2. What is the electron configuration for aluminum?

A. 1s²2s²2p⁶3s¹3p²

B. 1s²2s²2p⁶3s²3p²

C. 1s²2s²2p⁶3s³

D. 1s²2s²2p⁶3s²3p¹

3. As atoms bond with each other, they…

A. increase their potential energy.

B. move further apart.

C. lose their electron cloud.

D. decrease their potential energy, thus creating more-stable arrangements of matter.

4. If the atoms that share electrons have an unequal attraction for the electrons, the bond is called…

A. ionic.

B. nonpolar.

C. metallic.

D. polar.

5. An atom is electrically neutral because…

A. the number of neutrons equals the number of electrons.

B. the number of protons equals the number of neutrons.

D. the positive charge of the nucleus is balanced by the outer shell.

C. the numbers of protons and electrons are equal.

6. According to VSEPR theory, what is the shape of CH₄?

A. linear.

B. trigonal planar.

C. bent.

D. tetrahedral.

7. What is the formula for calcium oxide?

A. CaCl₂.

B. Ca₂O.

C. CO₂.

D. CaO.

8. Most of the mass of an atom is occupied by the…

A. electrons.

B. protons.

C. neutrons.

D. nucleus.

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9. The total number of protons and neutrons in the nucleus of a single atom is its…

A. atomic number.

B. electron number.

D. isotopic mass.

C. mass number.

10. A “packet” of electromagnetic radiation is called…

A. an atom.

B. a molecule.

C. an electron.

D. photon.

11. A line spectrum is produced when an electron moves from one energy level…

A. to a higher energy level.

C. to an equal energy level.

D. within the same orbital.

B. to a lower energy level.

12. The change of an atom from an excited state to the ground state always requires…

A. absorption of energy.

C. loss of mass.

D. formation of an isotope.

B. release of energy.

13. Which of the following orbital notations for phosphorus is correct?

A. The one with 1s², 2s², 2p⁶, 3s², 3p⁵.

B. The one with 1s², 2s², 2p⁶, 3s¹, 3p⁵.

D. The one with 1s², 2s², 2p⁶, 3s², 3p⁴.

C. The one with 1s², 2s², 2p⁶, 3s², 3p³.

14. The atomic number of lithium is 3. What is the atomic number of the next element in the same group?

A. 4 (beryllium).

B. 9 (fluorine).

D. 5 (boron).

C. 11 (sodium).

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15. An isotope of chlorine has an atomic number of 17 and a mass number of 35. Which is the correct set of subatomic particles?

A. 17 protons, 17 electrons, and 20 neutrons.

C. 16 protons, 16 electrons, and 18 neutrons.

D. 17 protons, 17 electrons, and 17 neutrons.

B. 17 protons, 17 electrons, and 18 neutrons.

16. How many atoms are equivalent to 3.5 mol of silicon?

A. 3.5 × 10²³ atoms.

B. 1.2 × 10²³ atoms.

C. 7.5 × 10²³ atoms.

D. 2.1 × 10²⁴ atoms.

17. Elements to the right side of the periodic table (p-block elements) have properties most associated with…

A. metals.

C. metalloids.

D. noble gases.

B. nonmetals.

18. The elements whose electron configurations end with s²p⁶ in the highest occupied energy level belong to Group…

A. 1 (alkali metals).

B. 2 (alkaline earth metals).

C. 17 (halogens).

D. 18 (noble gases).

19. As electrons add to s and p sublevels in the same main energy level, they are pulled closer to the nucleus, causing…

A. ionization energy to increase.

B. atomic mass to decrease.

D. the nucleus to become unstable.

C. atomic radii to decrease in size.

20. What is the correct, balanced equation when rubidium reacts with zinc nitrate?

A. Rb + Zn(NO₃)₂ → RbNO₃ + Zn.

C. Rb + Zn(NO₃)₂ → ZnRb + NO₃.

D. 2Rb + 3Zn(NO₃)₂ → 3Zn + Rb₂(NO₃)₃.

B. 2Rb + Zn(NO₃)₂ → Zn + 2RbNO₃.

21. What is a positive ion called?

A. anion.

B. isotope.

D. neutral atom.

C. cation.

22. In the three molecules, O₂, HCl, and F₂, which atom would have a partial negative charge?

A. oxygen (in O₂).

C. chlorine (in HCl).

D. hydrogen (in F₂).

B. hydrogen (in HCl).

23. Which type of reaction is this: 2KClO₃ → 2KCl + 3O₂?

A. synthesis.

C. combustion.

D. single displacement.

B. decomposition.

24. What are the products of this reaction: CH₄(g) + O₂(g)?

B. H₂(g) + CO(g).

C. CH₂(g) + O₂(g).

D. CH₄(g) + H₂O(l).

A. CO₂(g) + H₂O(g).

25. What does the chemical formula for an ionic compound represent?

A. The total number of protons in the crystal lattice.

B. The mass of the ions in the compound.

C. The number of atoms in each molecule.

D. The total number of ions in the crystal lattice.

26. Which group of elements satisfies the octet rule without forming compounds?

A. halogens.

C. alkali metals.

D. alkaline earth metals.

B. noble gases.

27. The ions in most ionic compounds are organized into a…

A. molecule.

B. polymer.

C. covalent bond.

D. crystal.

28. What is the correct, balanced equation when aluminum reacts with oxygen?

A. 4Al + O₂ → 2AlO₂.

B. 3Al + 3O₂ → Al₆O₃.

D. 2Al + 3O₂ → 2AlO₃.

C. 4Al + 3O₂ → 2Al₂O₃.

29. How many electrons must be shown in the Lewis structure of the hydroxide ion, OH⁻?

A. 6 electrons.

C. 7 electrons.

D. 10 electrons.

B. 8 electrons.

30. A rectangle has side measurements of 3.54 cm and 4.85 cm. What is the area of the rectangle to the correct number of significant figures?

A. 17 cm².

B. 18 cm².

C. 16.1 cm².

D. 17.2 cm².

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31. In an equation, the symbol for a substance dissolved in water is followed by…

A. (l).

B. (s).

C. (g).

D. (aq).

32. What is the term for a neutral group of atoms held together by covalent bonds?

A. crystal.

B. formula unit.

C. ion.

D. molecule.

33. Which coefficients balance this equation: NH₄NO₃ (s) → N₂ (g) + H₂O (l)?

A. 1, 2, 2.

B. 1, 1, 2.

C. 2, 1, 1.

D. 2, 2, 2.

34. Which statement best describes an element?

A. Any combination of two or more atoms of different types.

C. A substance containing only carbon atoms.

D. Any kind of crystal.

B. A pure substance made up of only one kind of atom.

35. What is the name of PbSO₄?

A. lead (II) sulfate.

C. lead oxide.

D. lead sulfide.

B. lead (II) sulfate.

36. Which of the following elements is NOT a metal?

A. H.

B. K.

D. Fr.

C. Na.

37. Name the compound KClO₃.

A. potassium chloride.

B. potassium trichlorate.

D. potassium chlorite.

C. potassium chlorate.

38. What is the percent composition of CF₄?

A. 20% C; 80% F.

B. 13.6% C; 86.4% F.

C. 16.8% C; 83.2% F.

D. 81% C; 19% F.

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39. In a chemical reaction…

A. the mass of the products is greater than the mass of the reactants.

B. the number of atoms in the reactants and products must change.

C. energy as heat must be added to the reactants.

D. the mass of the reactants equals the mass of the products.

40. In writing a chemical equation that produces hydrogen gas, which is the correct representation of hydrogen?

A. H.

B. 2H.

C. H₂.

D. OH.

41. Of the following molecular formulas for hydrocarbons, which is an empirical formula?

A. C₆H₆.

B. CH₄.

D. C₄H₁₀.

C. CH₂.

42. Which is the correct skeleton equation for showing that carbon and oxygen form carbon dioxide?

A. carbon + oxygen → carbon dioxide.

B. C (s) + O₂ (g) → CO₂ (g).

C. CO₂ (g) → C (s) + O₂ (g).

D. 2C (s) + O₂ (g) → CO₂ (g).

43. A three-dimensional region around a nucleus where an electron may be found is called…

A. a spectral line.

B. an electron path.

D. an orbit.

C. an orbital.

44. Why does atomic radius increase moving down a group?

A. The nuclear charge increases.

B. The number of neutrons increases.

D. A new octet forms.

C. The number of occupied energy levels increases.

45. How does the energy required to remove an electron from an atom change as you move across a period?

A. It generally increases.

C. It does not change.

D. It varies unpredictably.

B. It generally decreases.

46. Most of the volume of an atom is occupied by the…

A. nucleus.

B. nuclides.

D. protons.

C. electrons.

47. The atomic number of oxygen, 8, indicates that there are eight…

A. Protons in the nucleus of an oxygen atom

B. Oxygen nuclides

C. Neutrons outside the oxygen atom’s nucleus

D. Energy levels in the oxygen atom’s nucleus

48. If electrons in an atom have the lowest possible energies, the atom is in the…

A. Ground state

B. Inert state

C. Excited State

D. Radiation emitting State

49. Name the compound SO₃:

 A. Sulfur oxide 

B. Sulfur trioxide

C. Monosulfur trioxide

 D. Sulfur dioxide

50. What is the formula for diphosphorus pentoxide?

A. P₂P₅ 

B. P₂O₅ 

C. PO₅ 

D. P₂O₄