Chemistry-Semester Exam Review

1. Chemistry-Semester Exam Review Module 1

2. What is the difference between a scientific theory and law?

3. A scientific theoryis a set of ideas that attempts to explain why things happen the way they do in the natural world.  A law is a generalization that describes a variety of behaviors in nature, but does not attempt to explain.Examples: The theory of evolution and law of gravity.

4. What makes science different from other fields of knowledge?

5. The scientific method which is a systematic approach to problem solving.  Science is about observation to answer questions, unlike philosophy which does not need to be based upon observation.

6. How many significant figures do each of terms these have? • 0.005670 cm • 1.00 cm • 100 cm • 100.00 cm

7. Answers • 0.005670 cm (4 sig figs) • 1.00 cm (3 sig figs) • 100 cm (1 sig fig) • 100.00 cm (5 sig figs)

8. Five rules of sig figs. 1. 2. 3. 4. 5.

9. Five Rules of sig figs 1. Every non-zero is significant. 2. Any zero between non-zeroes is significant. 3. Any zero at the beginning of a number before the first non-zero is NOT significant. 4. Any zero at the end of a number without a decimal place is NOT significant. 5. Any zero at the end of a number with a decimal place is significant.

10. Rules of sig figs for addition and subtraction. • When adding or subtracting sig figs, you need to find the lowest number decimal places and then add or subtract and round your answer to that number of decimal places. • ex:  1.005 +  2.0074 = • ex:  1.005 -  2.0074 =

11. Answers • ex:  1.005 +  2.0074 = 3.0124  rounded to 3.012  (three decimal places) • ex:  1.005 -  2.0074 = -1.0024  rounded to -1.002  (three decimal places)

12. When multiplying or dividing sig figs, you need to find the lowest number of significant figures and then multiplying and dividing and round your answer to that number of significant figures. • ex:  1.005 * 2.0074 = • ex:  1.005 / 2.0074 =

13. Answers • ex:  1.005 * 2.0074 = 2.017437  rounded to  2.017 (four significant figures) • ex:  1.005 / 2.0074 = 0.500647603865697  rounded to  0.5006 (four significant figures)

14. Unit Conversion. • Can you convert 56.5 km to m?

15. Answer Can you convert 56.5 km to m? 56.5 km 1000 m = 56500 m 1 km

16. Unit Conversion • 500.5 ml to liters?

17. Answer • 500.5 ml to liters? 500.5 mL 1 x 10-3 L = 0.5005 1 mL

18. Chemistry Semester Exam Review Module 2

19. Why do theories change and evolve? A. No one believes the original theory. B. New technology or experimentation leads to revised ideas. C. If one scientist makes a discovery that challenges a theory it will change the theory. D. If certain important groups of people think that the theory is wrong, the theory will be considered invalid.

20. Why do theories change and evolve? A. No one believes the original theory. B. New technology or experimentation leads to revised ideas. C. If one scientist makes a discovery that challenges a theory it will change the theory. D. If certain important groups of people think that the theory is wrong, the theory will be considered invalid.

21. What are models? Why do scientists use them? A. Models are useful for scientists that can’t collect real data B. Models allow scientists to predict reactions without making real life observations. C. Models are used as visual representations of something very small or very large. Something that isn’t easy to see or observe. D. Models help scientists study things without having to conduct experiments or collect data.

22. What are models? Why do scientists use them? A. Models are useful for scientists that can’t collect real data B. Models allow scientists to predict reactions without making real life observations. C. Models are used as visual representations of something very small or very large. Something that isn’t easy to see or observe. D. Models help scientists study things without having to conduct experiments or collect data.

23. Describe the main points of Dalton’s atomic theory and what points have changed as a result of experiments performed later. Include details of those experiments such as their expected and observed results and the scientists credited with those discoveries.

24. Dalton’s Theory: • All matter is composed of extremely small particles called atoms. • Atoms of a given element are identical in size, mass and other properties. • Scientists now know that all atoms of a given element have the same number of protons but may have different numbers of neutrons (isotopes). • Atoms cannot be subdivided, created, or destroyed. • Scientists now know that atoms are divisible and made up of smaller, subatomic particles. However, the law of conservation of mass still states that matter cannot be created or destroyed in an ordinary chemical reaction. • Atoms of different elements can combine in simple, whole-number ratios to form chemical compounds. • In chemical reactions, atoms are combined, separated, or rearranged. • Others/Changes: • The cathode ray experiments resulted in Thomson adding electrons to the atomic model. • Rutherford’s gold foil experiment disproved Thomson’s plum pudding model by demonstrating that the mass of an atom is packed into a small, positive nucleus. He added the nucleus to the model of that atom, surrounded by electrons. • Bohr’s observation of the line spectra led to his idea that electrons exist on orbits around the nucleus, which he added to the model of the atom. • Schrodinger’s quantum model resulted from experiments that demonstrated the dual nature of light and the electron. He added energy levels and orbitals to the electron cloud surrounding the nucleus.

25. A neutral atom has the atomic number 14 and a mass number of 31, how many protons, neutrons, and electrons are found within the atom?

26. A neutral atom has the atomic number 14 and a mass number of 31, how many protons, neutrons, and electrons are found within the atom? Protons: 14, neutrons : 17 (31-14 = 17), electrons : 14

27. An atom is determined to contain 8 protons, 10 electrons, and 9 neutrons. What are the atomic number, mass number and charge of this atom or ion? A. atomic number: 8 mass number: 17, charge: -2 B. atomic number 9, mass number: 27, charge: neutral +1 C. atomic number 10, mass number: 17, charge: +2 D. atomic number 8, mass number: 27, charge: -2

28. An atom is determined to contain 8 protons, 10 electrons, and 9 neutrons. What are the atomic number, mass number and charge of this atom or ion? A. atomic number: 8 mass number: 17, charge: -2 B. atomic number 9, mass number: 27, charge: neutral +1 C. atomic number 10, mass number: 17, charge: +2 D. atomic number 8, mass number: 27, charge: -2

29. How many grams of carbon (C) are present in a sample of 2.5 × 1024 atoms C?

30. How many grams of carbon (C) are present in a sample of 2.5 × 1024 atoms C? • 49.9 g C

31. Which of the following contains the greatest number of moles? A. 6.02 × 1023 atoms Ag B. 5.1 mol Ag C. 0.3 mol Fe D. 125 g Fe

32. Which of the following contains the greatest number of moles? A. 6.02 × 1023 atoms Ag B. 5.1 mol Ag C. 0.3 mol Fe D. 125 g Fe

33. When an element is heated in a Bunsen burner flame, the resulting color of the flame changes can be used to identify the element. What causes the colored light that is observed?

34. When an element is heated in a Bunsen burner flame, the resulting color of the flame changes can be used to identify the element. What causes the colored light that is observed? When an electron moves from a higher to lower orbital, energy is released as waves of light.

35. What occurs when an excited electron returns to its ground state? A. Protons are released B. Energy is emitted as photons of light C. It transfers to another atom D. The electron is no longer able to bond

36. What occurs when an excited electron returns to its ground state? A. Protons are released B. Energy is emitted as photons of light C. It transfers to another atom D. The electron is no longer able to bond

37. How are the frequency, wavelength and energy of an electromagnetic wave related? • As frequency __________, energy __________ • As wavelength _________, energy __________ • As frequency _________, wavelength _________

38. How are the frequency, wavelength and energy of an electromagnetic wave related? • As frequency increases, energy increases • As wavelength increases, energy decreases • As frequency increases, wavelength decreases

39. What would be the most likely charge of an ion formed from an atom with the electron configuration: 1s2 2s2 2p5 A. +2 B. -2 C. +1 D. -1

40. What would be the most likely charge of an ion formed from an atom with the electron configuration: 1s2 2s2 2p5 A. +2 B. -2 C. +1 D. -1

41. Chemistry Semester One Exam Review Module 3

42. Periodic Trends 1). Atomic radius/atomic size. 2). Ionization energy 3). Electronegativity

43. Periodic Trends 1). Atomic radius/atomic size. There is a gradual decrease in atomic radii from left to right across a period. There is a general increase in atomic radii going down each group of elements on the periodic table. 2). Ionization energy Ionization energy has a general increase for elements across a period from left to right. The ionization energy of elements decreases going down a group because the atomic radius of the atoms increases 3). Electronegativity Electronegativity increases from left to right across a period because of the increase in effective nuclear charge. Electronegativity decreases down a group, as a result of increased distance between the valence electrons and the nucleus (greater atomic radius).

44. Write the name of the following compounds • CO2 • Ba3(PO4)2 • CuO • CaSO45H2O,

45. Write the name of the following compuonds • CO2 carbon dioxide • Ba3(PO4)2 barium phosphate • CuOcopper (II) oxide • CaSO4 5H2O calcium sulfate pentahydrate

46. Write the formula of the following compounds 1). magnesium phosphide 2). iodine dichloride 3). nitric acid 4). tin (IV) nitrate 5). potassium nitrate tetrahydrate. 

47. Write the formula of the following compounds 1). magnesium phosphideMg3P2 2). iodine dichloride ICl2 3). nitric acid HNO3 4). tin (IV) nitrate Sn(NO3)4 5). potassium nitrate tetrahydrateKNO3   3H2O

48. Which compound will experience hydrogen bonding? • HCl • C6H6 • HF • H2SO4

49. Which compound will experience hydrogen bonding? • HCl • C6H6 • HF • H2SO4

50. Draw Lewis Dot Structures for the following compounds • HCN • H2O • O3