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1. Question If matter is uniform throughout and cannot be separated into other substances by physical means, it is ________. Answer : Either an element or a compound. Explanation : Uniform matter that cannot be separated physically is classified as a pure substance. Pure substances are either: Elements : Made of one type of atom and cannot be further broken down. Example: Gold (Au). Compounds : Made of two or more elements chemically combined in a fixed ratio. Example: Water (H₂O). 2. Question Which of the following is an illustration of the law of definite proportions (constant composition)? Answer : Water is 11% hydrogen and 89% oxygen by mass. Explanation : The law of definite proportions states that a chemical compound always contains its elements in a fixed mass ratio. For water, the ratio of hydrogen (11% by mass) to oxygen (89% by mass) remains constant regardless of the source or quantity. 3. Question Which one of the following is an intensive property? Answer : Temperature. Explanation : Intensive properties do not depend on the amount of matter present. For example: Temperature remains the same regardless of how much of the substance is measured, unlike extensive properties like mass or volume, which vary based on quantity. 4. Question Temperatures in degrees Celsius (°C) and temperature in Kelvins (K)? Answer : K = °C + 273.15. Explanation : The Kelvin scale is an absolute temperature scale. To convert Celsius to Kelvin:
Add 273.15 to the Celsius value. For example: o 0°C = 273.15 K, 100°C = 373.15 K.
5. Question A combination of sand, salt, and water is an example of a ________. Answer : Heterogeneous mixture. Explanation : A heterogeneous mixture consists of substances that are unevenly distributed and can be physically separated. In this case: Sand and salt particles remain distinct within water, creating a mixture that is not uniform throughout. 6. Question Precision refers to ________. Answer : How close a measured number is to other measured numbers. Explanation : Precision measures the consistency and reproducibility of repeated measurements, regardless of their accuracy. For example, if three measurements of a length are 5.23 m, 5.24 m, and 5.22 m, the values are precise due to their closeness to one another. 7. Question Acceleration due to gravity of a free-falling object is 9.8 m/s². Express this in millimeters/millisecond². Answer : 9.8×10 −39.8 \times 10^{-3}. Explanation : Convert 9.8 m/s29.8 , \text{m/s}^2 to millimeters/millisecond²: 1 meter = 1000 millimeters. 1 second = 1000 milliseconds. 9.8 m/s2=9.8 mm/ms2=9.8×10 − 3 mm/ms2.9.8 , \text{m/s}^2 = 9.8 , \text{mm/ms}^2 = 9.8 \times 10^{-3} , \text{mm/ms}^2. 8. Question
12. Question ________ is an abbreviation for the power of ten equal to 10 −310^{-3}. Answer : mm. Explanation : In the metric system, mm (milli-) represents 10 −310^{- 3}. For example, 1 millimeter (mm) = 10 −310^{-3} meters. 13. Question 3.337 g/cm3= 3.337 , \text{g/cm}^3 = , ________ kg/m3, \text{kg/m}^ Answer : 3337. Explanation : To convert g/cm3\text{g/cm}^3 to kg/m3\text{kg/m}^3: o 1 g/cm3=1000 kg/m3\text{g/cm}^3 = 1000 , \text{kg/m}^3. 3.337 g/cm3×1000=3337 kg/m3.3.337 , \text{g/cm}^3 \times 1000 = 3337 ,
text{kg/m}^3. 14. Question The correct answer (reported to the proper number of significant figures) to the following is ________. (2.01)(6.936)12= ?\frac{(2.01)(6.936)}{12} = ,? Answer : 1.2. Explanation : Perform the multiplication and division: (2.01)(6.936)12=1.16163.\frac{(2.01)(6.936)}{12} = 1.16163. Round to 2 significant figures based on the least precise value (2.01). 15. Question The correct answer (reported to the proper number of significant figures) to the following is ________. (12.67+19.2)(3.99)(1.36+11.366)= ?\frac{(12.67 + 19.2)(3.99)}{(1.36 + 11.366)} = ,? Answer : 9.99. Explanation : Add numbers in parentheses:
(12.67+19.2)=31.87and(1.36+11.366)=12.726.(12.67 + 19.2) = 31.87 \quad \text{and} \quad (1.36 + 11.366) = 12.726. Perform the multiplication and division: (31.87)(3.99)12.726=9.99.\frac{(31.87)(3.99)}{12.726} = 9.99. Round to 3 significant figures.
16. Question The correct result (indicating the proper number of significant figures) of the following addition is ________. 12+1.2+0.12+0.012.12 + 1.2 + 0.12 + 0.012. Answer : 13. Explanation : Add the numbers: 12+1.2+0.12+0.012=13.332.12 + 1.2 + 0.12 + 0.012 = 13.332. Round to the least number of decimal places (0 decimal places for "12"), resulting in 13. 17. Question An object measuring 0.4500 kilograms0.4500 , \text{kilograms} will have a mass of ________ grams\text{grams}. Answer : 450.0. Explanation : Convert kilograms to grams using: 1 kg=1000 g.1 , \text{kg} = 1000 , \text{g}. 0.4500 kg×1000=450.0 g.0.4500 , \text{kg} \times 1000 = 450.0 , \text{g}. 18. Question How many significant figures are in the measurement 5000 g?5000 , \text{g}? Answer : 1. Explanation : If no decimal point is shown, trailing zeros are not significant. Only the digit "5" is significant, meaning there is 1 significant figure.
Isotopes of an element have the same number of protons (atomic number) but a different number of neutrons , leading to a difference in mass numbers. For example, carbon-12 and carbon-14 are isotopes of carbon.
23. Question The element X has three naturally occurring isotopes. The masses (amu) and % abundances of the isotopes are given in the table below. The average atomic mass of the element is ________ amu. Answer : 220.4 amu. Explanation : Average atomic mass is calculated using the formula: Average Atomic Mass= ∑(Fractional Abundance×Isotopic Mass).\text{Average Atomic Mass} = \sum \left( \text{Fractional Abundance} \times \text{Isotopic Mass} \right). If the isotopes and their abundances are provided, substitute their values into the equation and compute the sum. 24. Question In the periodic table, the elements are arranged in ________. Answer : Order of increasing atomic number. Explanation : The modern periodic table is organized based on the atomic number, which is the number of protons in an atom's nucleus. This arrangement reflects periodic trends in chemical and physical properties. 25. Question Elements ________ exhibit similar physical and chemical properties. Answer : In the same group of the periodic table. Explanation : Elements within the same group (vertical column) have similar properties because they share the same number of valence electrons, which determine chemical reactivity. For instance, alkali metals (Group 1A) react similarly with water. 26. Question
Which pair of elements would you expect to exhibit the greatest similarity in their physical and chemical properties? Answer : Ca and Sr. Explanation : Calcium (Ca) and Strontium (Sr) belong to Group 2A, the alkaline earth metals. Elements in the same group have similar properties due to their identical valence electron configuration.
27. Question An element in the upper right corner of the periodic table ________. Answer : Is definitely a nonmetal. Explanation : The upper right corner of the periodic table includes nonmetals such as oxygen, fluorine, and neon. These elements typically have high electronegativity and ionization energy and do not conduct electricity. 28. Question Which one of the following molecular formulas is also an empirical formula? Answer : C2H6SOC_2H_6SO. Explanation : A molecular formula represents the actual number of atoms in a compound. If the ratio of atoms cannot be simplified further, the molecular formula is also the empirical formula. For C2H6SOC_2H_6SO, the ratio 2:6:1:12:6:1:1 is already in its simplest form. 29. Question Of the following, ________ contains the greatest number of electrons. Answer : P3 −P^{3-}. Explanation : To determine the total number of electrons: o Start with the number of protons (atomic number). For phosphorus (PP), the atomic number is 15. o Add or subtract the charge to get the total electrons. For P3 −P^{3-}: 15+3=18 electrons.15 + 3 = 18 , \text{electrons}.
35. Question The correct name for HNO₂ is ________. Answer : Nitrous acid. Explanation : Acids containing anions ending in -ite are named with the suffix -ous. NO₂⁻ is nitrite, so HNO₂ is nitrous acid. 36. Question Which one of the following polyatomic ions has the same charge as the hydroxide ion? Answer : Nitrate. Explanation : Hydroxide (OH⁻) and nitrate (NO₃⁻) both have a charge of -1. 37. Question Elements in Group 1A are known as the ________. Answer : Alkali metals. Explanation : Group 1A elements, like lithium and sodium, are soft metals with high reactivity, particularly with water. 38. Question Potassium is a ________ and chlorine is a ________. Answer : Metal, nonmetal. Explanation : Potassium (K) is located on the left side of the periodic table, classifying it as a metal. Chlorine (Cl) is on the right side, making it a nonmetal. 39. Question When a metal and a nonmetal react, the ________ tends to lose electrons and the ________ tends to gain electrons. Answer : Metal, nonmetal. Explanation : Metals typically lose electrons to achieve a stable configuration, while nonmetals gain electrons. 40. Question What is the formula of the compound formed between strontium ions and nitrogen ions?
Answer : Sr₃N₂. Explanation : Strontium (Sr²⁺) forms a compound with nitrogen (N³⁻). To balance charges, three Sr²⁺ ions combine with two N³⁻ ions.
41. Question Magnesium reacts with a certain element to form a compound with the general formula MgX. What would the most likely formula be for the compound formed between potassium and element X? Answer : K₂X. Explanation : Magnesium (Mg²⁺) and potassium (K⁺) form compounds where their charges balance. For X with a -2 charge, two potassium ions are needed. 42. Question The charge on the manganese in the salt MnF₃ is ________. Answer : 3⁺. Explanation : Fluoride (F⁻) has a charge of -1. With three fluoride ions (total charge -3), manganese must have a +3 charge to balance. 43. Question The correct name for K₂S is ________. Answer : Potassium sulfide. Explanation : Ionic compounds are named with the metal (cation) followed by the nonmetal (anion). Sulfide refers to S²⁻. 44. Question The correct name for CCl₄ is ________. Answer : Carbon tetrachloride. Explanation : In molecular compounds, prefixes indicate the number of atoms. Tetra- means four chlorine atoms bonded to carbon. 45. Question The correct name for H₂SO₄ is ________. Answer : Sulfuric acid. Explanation : Acids containing anions ending in -ate are named with the suffix -ic. SO₄²⁻ is sulfate, so H₂SO₄ is sulfuric acid. 46. Question
The formula of nitrobenzene is C6H5NO2C_6H_5NO_2. The molecular weight of this compound is ________ amu. Answer : 123.11 amu. Explanation : To calculate molecular weight: Weight=(C×12.01)+(H×1.008)+(N×14.01)+(O×16.00).\text{Weight} = (\text{C} \times 12.01) + (\text{H} \times 1.008) + (\text{N} \times 14.01) + (\text{O} \times 16.00). Substituting values gives 123.11 amu.
53. Question The formula weight of potassium dichromate (K2Cr2O7K_2Cr_2O_7) is ________ amu. Answer : 294.18 amu. Explanation : Formula weight is calculated by summing the atomic weights: 2(K)+2(Cr)+7(O)=294.18 amu.2(K) + 2(Cr) + 7(O) = 294.18 , \text{amu}. 54. Question Which of the following contains the largest number of atoms in a mole? Answer : Al2(SO4)3Al_2(SO_4)_3. Explanation : Al2(SO4)3Al_2(SO_4)_3 contains: o 2 Al2 , \text{Al} + 3×(1 S+4 O)=17 atoms per formula unit3 \times (1 ,
text{S} + 4 , \text{O}) = 17 , \text{atoms per formula unit}. o A mole of this compound contains 17×6.022×102317 \times 6.022
times 10^{23} atoms, the largest amount among options. 55. Question How many molecules of CH4CH_4 are in 48.2 g of this compound? Answer : 1.81×10241.81 \times 10^{24}. Explanation : To find the number of molecules: Calculate moles:
Moles=MassMolar Mass=48.216.04.\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} = \frac{48.2}{16.04}. Multiply moles by Avogadro's number: 1.81×1024 molecules.1.81 \times 10^{24} , \text{molecules}.
56. Question A sample of CH4OCH_4O with a mass of 32.0 g contains ________ molecules of CH4OCH_4O. Answer : 6.02×10236.02 \times 10^{23}. Explanation : Molar mass of CH4OCH_4O is 32.04 g/mol. One mole contains 6.022×10236.022 \times 10^{23} molecules. 57. Question The compound responsible for the characteristic smell of garlic is allicin (C6H10OS2C_6H_{10}OS_2). What is the mass (g) of 1.00 mol of allicin? Answer : 162 g. Explanation : Molar mass is calculated as: (6×12.01)+(10×1.008)+(16.00)+(2×32.07)=162 g/mol.(6 \times 12.01) + (10 \times 1.008) + (16.00) + (2 \times 32.07) = 162 , \text{g/mol}. 58. Question The molecular formula of aspartame (NutraSweet®) is C14H18N2O5C_{14}H_{18}N_2O_5. What is the mass (g) of 1.00 mol of aspartame? Answer : 294 g. Explanation : Add the atomic weights of all atoms: (14×12.01)+(18×1.008)+(2×14.01)+(5×16.00)=294 g/mol.(14 \times 12.01) + (18
times 1.008) + (2 \times 14.01) + (5 \times 16.00) = 294 , \text{g/mol}. 59. Question The formula weight of Zn(ClO4)2Zn(ClO_4)_2 is ________ amu.
63. Question Calculate the percentage by mass of oxygen in Pb(NO3)2Pb(NO_3)_2. Answer : 29.0%. Explanation : Determine the total molar mass of Pb(NO3)2Pb(NO_3)_2: Pb: 207.2 g/mol,N: 2×14.01 g/mol,O: 6×16.00 g/mol.\text{Pb: } 207.2 , \text{g/mol}, \quad \text{N: } 2 \times 14.01 , \text{g/mol}, \quad \text{O: } 6
times 16.00 , \text{g/mol}. Total mass = 331.22 g/mol331.22 , \text{g/mol}. Mass % of oxygen: \text{Mass %} = \frac{\text{Mass of O}}{\text{Total mass}} \times 100 = \frac{96.00} {331.22} \times 100 = 29.0%. 64. Question What is the empirical formula of a compound that contains 27.0% S, 13.4% O, and 59.6% Cl by mass? Answer : SOCl2SOCl_2. Explanation : Convert % to moles for each element: S: 27.032.07,O: 13.416.00,Cl: 59.635.45.\text{S: } \frac{27.0}{32.07}, \quad
text{O: } \frac{13.4}{16.00}, \quad \text{Cl: } \frac{59.6}{35.45}. Find the simplest ratio, yielding SOCl2SOCl_2. 65. Question The molecular formula of a compound with 40.0% C, 6.71% H, and 53.29% O by mass and a molecular weight of 60.05 amu is ________. Answer : C2H4O2C_2H_4O_2. Explanation : Use the same steps as for empirical formula, then compare the molecular weight of the empirical formula to the compound's molecular weight to find the molecular formula.
66. Question An electron cannot have the quantum numbers n=1, l=1, ml=1n = 1, , l = 1, , m_l =
Answer : n=1, l=1, ml=1n = 1, , l = 1, , m_l = 1. Explanation : The quantum number ll must be less than nn, so when n=1n = 1, ll can only be 0. This set of quantum numbers violates that rule. 67. Question Of the following, ________ radiation has the shortest wavelength. Answer : X-ray. Explanation : Radiation types are ranked by wavelength: gamma rays have the shortest, followed by X-rays, ultraviolet, visible light, and so on. 68. Question In a pxp_x orbital, the subscript xx denotes the ________. Answer : Axis along which the orbital is aligned. Explanation : pxp_x orbitals are oriented along the x-axis, while pyp_y and pzp_z align along the y- and z-axes, respectively. 69. Question Which electron configuration represents a violation of the Pauli exclusion principle? Answer : Any configuration where two electrons in the same orbital have identical spin quantum numbers. Explanation : The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers. 70. Question The ground-state electron configuration of Ga is ________. Answer : 1s22s22p63s23p64s23d104p11s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^1. Explanation : Gallium has 31 electrons distributed according to the Aufbau principle, filling orbitals in the correct order. 71. Question
Answer : Hydrogen atom. Explanation : The de Broglie wavelength is inversely proportional to the mass of the object. Hydrogen atoms have the smallest mass among the options, resulting in the longest wavelength.
76. Question The wavelength of light that has a frequency of 1.20×1013 s −11.20 \times 10^{13} , \text{s}^{-1} is ________ m. Answer : 2.50×10 −52.50 \times 10^{-5}. Explanation : Use the formula: Wavelength=Speed of LightFrequency=3.00×1081.20×1013.\text{Wavelength} =
frac{\text{Speed of Light}}{\text{Frequency}} = \frac{3.00 \times 10^8}{1.20 \times 10^{13}}. 77. Question A mole of red photons of wavelength 725 nm725 , \text{nm} has ________ kJ of energy. Answer : 165 kJ. Explanation : Calculate the energy using: E=hcλ.E = \frac{hc}{\lambda}. Convert EE to kJ for a mole of photons. 78. Question What is the wavelength (nm) of light emitted when an electron in a hydrogen atom moves from n=4n = 4 to n=2n = 2? Answer : 486 nm. Explanation : Use the Rydberg formula to calculate the wavelength: 1λ=R(1n12 −1n22),\frac{1}{\lambda} = R \left( \frac{1}{n_1^2} - \frac{1}{n_2^2}
right), where RR is the Rydberg constant. 79. Question A 34.0 mg34.0 , \text{mg} object with a de Broglie wavelength of is traveling at what speed?
Answer : 8.12×10 − 7 m/s8.12 \times 10^{-7} , \text{m/s}. Explanation : Use the de Broglie wavelength formula: λ=hmv.\lambda = \frac{h}{mv}.
80. Question There are ________ orbitals in the third shell. Answer : 9. Explanation : The third shell (n=3n = 3) contains orbitals defined by l=0,1,2l = 0, 1, 2, for a total of: 1+3+5=9 orbitals.1 + 3 + 5 = 9 , \text{orbitals}. 81. Question Each pp-subshell can accommodate a maximum of ________ electrons. Answer : 6. Explanation : A pp-subshell contains three orbitals (px,py,pzp_x, p_y, p_z), each capable of holding two electrons. Hence, the total capacity of a pp- subshell is: 3 orbitals×2 electrons/orbital=6 electrons.3 , \text{orbitals} \times 2 ,
text{electrons/orbital} = 6 , \text{electrons}. 82. Question [Ar]4s23d104p3[Ar]4s^23d^{10}4p^3 is the electron configuration of a(n) ________ atom. Answer : Arsenic (As). Explanation : The element arsenic has an atomic number of 33, and this configuration represents the distribution of its electrons across various energy levels. 83. Question What is the actual ground-state electron configuration for chromium? Answer : [Ar]4s13d5[Ar]4s^13d^5. Explanation : Chromium (Cr) has an atomic number of 24. It adopts this configuration due to stability gained from half-filled dd-orbitals. 84. Question
