Chemistry 11: Chemical Reactions

Alex Obray
Flashcards by Alex Obray, updated more than 1 year ago
Alex Obray
Created by Alex Obray over 5 years ago
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Flashcards on Chemistry 11: Chemical Reactions, created by Alex Obray on 02/19/2016.

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Question Answer
1. Difference and examples of: Qualitative Quantatitive 1. Qualitative properties are descriptive. e.g. state, colour, odour, texture taste Quantitative properties are measurable. e.g. density, heat conduction, volatility, boiling point, melting point
2. What is a physical change? Examples. A change in which no new substance is produced. The substance may have some different properties afterwards, but it is still the same substance. e.g. changes of state, bending a nail, breaking a window, tearing paper, melting ice
3. What are chemical properties of matter? Examples? Properties which describe how a substance will react or undergo chemical changes. These properties can vary greatly from one substance to another. Adding potassium to water produces hydrogen and potassium hydroxide. Therefore, this is a chemical reaction. Adding Alka-Seltzer to water releases a gas. Therefore, this is a chemical reaction. Adding sodium chloride to water produces no observable changes. Therefore, it is not a chemical reaction.
4. What is a chemical change? Examples. Results in the formation of a new substance with different physical and chemical properties than the initial substances e.g. change of colour, heat is released (exothermic), heat is absorbed (endothermic), light is produced, a precipitate is formed, a gas is produced (bubbling) change of smell
5. How do most chemical reactions take place? Most chemical reactions take place when particles of reactants collide with enough force to react. Bonds between atoms are broken and new bonds form between different atoms.
6. The statement “methanol boils at 780C” is an example of a: physical property physical change chemical property chemical change physical property
7. The statement “phosphorus ignites in contact with air” is an example of a: physical property physical change chemical property chemical change chemical change
8. The statement “oxygen supports combustion” is an example of a: physical property physical change chemical property chemical change chemical property
9. The statement “melting ice” is an example of a: physical property physical change chemical property chemical change physical change
10. During a chemical reaction, at least one new substance is formed. What is a reactant? What is a product? The substances that undergo the reaction are called reactants. The new substances that are formed are called products.
11. Write a chemical equation for the following reaction: “iron filings react with sulphuric acid to produce hydrogen and iron(II) sulphate iron + sulphuric acid arrow hydrogen + iron (II) sulphate Fe + H2SO4 -------> H2 + FeSO4
12. Follow these steps when writing a chemical equation: What are the steps for writing a chemical equation? -Write the correct chemical formulas for the chemicals involved. -Determine which chemicals are the reactants, and which are the products. -Write the reactants to the left of the arrow, and the products to the right of the arrow.
13. What is the law of conservation of mass? What is an explanation when a reaction appears to gain or lose mass? This law states that matter cannot be created, or destroyed, during a chemical reaction. All atoms present in the reactants are also present in the products. Reactions that seem to gain, or lose, mass actually involve reactions with gases in the air. Although these gases cannot be seen, their masses can be measured.
14. What are the four main types of chemical reactions? Synthesis reactions Decomposition reactions Single displacement reactions Double displacement reactions
15. What is a synthesis reaction? What can they also be called? How is a compound formed? Reactants combine together to form a new substance. Synthesis reactions can also be called addition reactions or combination reactions. A new compound is formed by the combinations of simpler reactions, making a substance from simpler substances
13. What is the law of conservation of mass? What is the explanation for when a reaction appears to have gained or lose mass? This law states that matter cannot be created, or destroyed, during a chemical reaction. All atoms present in the reactants are also present in the products. Reactions that seem to gain, or lose, mass actually involve reactions with gases in the air. Although these gases cannot be seen, their masses can be measured.
14. What are the four different types of chemical reactions? Synthesis reactions Decomposition reactions Single displacement reactions Double displacement reactions
15. What is a synthesis reactions? (Example) What are alternative names for this reaction? How is a new compound formed? reactants combine together to form a new substance. E.g. C + O2 = CO2 Synthesis reactions can also be called addition reactions or combination reactions. A new compound is formed by the combinations of simpler reactions, making a substance from simpler substances.
16. What is a Decomposition Reaction? (Example) The lone reactant breaks up into smaller molecules. It can be thought of as being a reverse of synthesis reactions. e.g. 2H2O -> 2H2 + O2
17. What is a single displacement reaction? (Example) In a single displacement reaction, one of the reactants is an element, which displaces another element from a reactant compound. e.g. Magnesium can displace hydrogen from sulphuric acid: Mg + H2SO4 -> MgSO4 + H2
18. What is a Double Displacement Reaction? (Example) In a double displacement reaction, atoms or groups are exchanged between two reactants. E.g. neutralization reactions and precipitation reactions Sodium hydroxide is neutralized by hydrochloric acid to produce salt and water NaOH + HCl -> NaCl + H2O
19. What is a precipitate? A precipitate is a substance that is formed during a chemical reaction, and which remains insoluble in the solution. It is a solid which deposits to the bottom or sides of the container, or may remain suspended within the solution.
20. What type of reaction is the following? 2Mg + O2 -> 2MgO synthesis decomposition single displacement double displacement synthesis
21. What type of reaction is the following? 2HCl + Na2CO3 -> 2NaCl + H2CO3 synthesis decomposition single displacement double displacement double displacement
22. State the missing reactant in the following single displacement reaction. Blank + 3Fe -> Fe3O4 + 4H2 4H2O
23. State the missing reactant in the following decomposition reaction. 4HNO3, -> blank + 2H2O + O2 4NO2
24. During chemical reactions, there is almost always some type of absorption or release of energy. List some examples that energy can be in the form of? heat (most of the time) light electricity sound or others.
25. What is an endothermic reaction? The symbol Q in a chemical equation is a generic representation for energy in the form of heat. Where is it placed in chemical equation for endothermic reactions? (Examples) Endothermic reactions are reactions which need energy in order to take place. They absorb energy. It is placed to the left of the reaction arrow
26. What are exothermic reactions? The symbol Q in a chemical equation is a generic representation for energy in the form of heat. Where is it placed in chemical equation for exothermic reactions? (Examples) Reactions that produce energy when they take place. They release energy and so the symbol Q is placed to the right of the reaction arrow as shown in the two combustion reactions below. E.g. double displacement reaction, synthesis reaction
27. Why do animals require oxygen? What does oxygen require? in order to carry out the chemical process of cellular respiration in which we react sugar with oxygen to liberate energy. plants, since they release oxygen as a waste product through the process of photosynthesis which makes the sugar in the first place.
28. What is the unbalanced chemical equation for respiration?
29. What is the unbalanced chemical equation for photosynthesis?
30. What is oxidation? Give examples of oxidation Oxidation is the reaction of element and compounds with oxygen rusting and rotting
31. When is oxidation considered combustion? When oxidation occurs quickly, and is accompanied by large amounts of heat and light, it is called combustion
32. When does a combustion reaction occur? When a substance, such as a hydrocarbon, is burned in oxygen.
33. When metals are burned they produce... a metal oxide.
34. When non-metals are burned... a non-metal oxide.
35. When will hydrocarbon combust completely? If there is a sufficient amount of oxygen and heat present
36. What is released in a complete combustion? Great amounts of carbon dioxide gas and water are released
37. What has rising carbon dioxide gas levels been linked to? to an enhanced greenhouse effect and the overall rise in atmospheric temperatures, the result of which is global warming.
38. When does incomplete combustion take place? Without sufficient oxygen present
39. Incomplete combustion results in two additional substances being produced: carbon and carbon monoxide
40. Oxygen gas is formed when two atoms of oxygen bond together. True
41. Oxygen gas may participate in chemical reactions as either a reactant or product. True
41. Combustion is a chemical reaction that takes place slowly and releases oxygen gas. False…combustion occurs rapidly and releases carbon dioxide and water.
42. As long as fuels burn completely, there is no environmental risk or damage. False…carbon dioxide contributes to the enhanced greenhouse effect.
43. Carbon monoxide gas is extremely dangerous and difficult to detect. True
44. Write the balanced chemical equation for combustion of C7H6O.
45. What is an oxidation reaction? When an element or compound combines with oxygen
46. Most metal oxides are _________ that react with water to form ________, and are called ______ ionic compounds hydroxides Basic oxides
47. Non-metal oxides tend to be... Give a few examples gases, liquids or low-melting solids carbon dioxide (in air), nitrogen dioxide (in smog) and sulphur trioxide (pollutant that causes acid rain).
48. Give a few examples of metal oxides iron interacts with oxygen to form rust. Copper can also "rust" but its oxide is green.
49. Where is nitrogen dioxide found? Nitrogen dioxide is a component of smog and forms when nitrogen and oxygen combine in the air.
50. Non-metal oxides react with water to form ___, so they are called ____. acid acidic oxides
51. Which one of the following oxides is considered to be acidic? CaO SrO CO2 Na2O c. CO2
52. Copper(II) oxide is more acidic than carbon dioxide. False The copper(II) oxide is more basic than carbon dioxide.
53. Phosphorus pentoxide is more basic than sulphur trioxide. True Metallic properties increase in the periodic table from right to left. Therefore, oxides formed with elements to the left of the table will be more basic. Phosphorus is to the left of sulphur, so its oxide is more basic.
54. Molecules that contain an H+ ion, such as HCl and H2SO4, are called _____________. Molecules that contain an OH- ion, such as NaOH and Ba(OH)2 are called _____________. acids bases
55. What is a neutralization reaction? A reaction in which a hydrogen ion neutralizes a hydroxide ion "A neutralization reaction is when an acid and a base react to form water and a salt and involves the combination of H+ ions and OH- ions to generate water. " acid + base ---> salt + water e.g. HCl + NaOh --> NaCl + H2O
56. What are spectator ions? When they play no part in the neutralization process.
57. Some common examples and applications of neutralization are: acid cleanup of acid spills cooking, such as adding lemon juice (acidic) to fish (basic) antacids to neutralize stomach
58. Will 1 mL of acid neutralize 1 mL of any base Not necessarily. It depends on their nature and their concentration
59. How do you dilute an acid or base? Adding pure water lowers the concentration of the charged H+ and OH- ions in the solution.
60. If there are H+ ions left over after the neutralization reaction, then the solution is _____ acidic
61. If there are OH- ions left over after the neutralization reaction, then the solution is _____ basic
62. What are the products of the following neutralization reaction? H2SO4 + RbOH --> Rb2SO4 + 2H2O
63. What did Avagardo state regarding the volume of gases? Equal volumes of gases, at the same temperature and pressure, contain the same number of molecules regardless of their chemical nature and physical properties.
64. Avogadro's number 6.022 x 10^23
65. one mole contains as many entities as there are ... one mole contains as many entities as there are in 12 g of carbon-12 (or 0.012 kg). There are 6.022 x 10^23atoms in 12 g of carbon-12.
66. How many atoms are in 0.5 mol of sodium?
67. How many moles of magnesium are there in 3.01 x 1022 atoms of magnesium?
68. How many moles of tungsten correspond to 5.05 x 10^20 atoms? 5.05 x 10^20 atoms x 1 mol/6.02 x 10^23 atoms = 0.000839 mol of W
69. Formula for molar mass
70. What is molar mass? The mass of one mole of a substance
71. Calculate the molar mass of Al(NO3)3. There is 1 atom of Al There are 3 atoms of N There are 9 atoms of O The atomic mass of Al is 26.9815 g/mol The atomic mass of N is 14.0067 g/mol The atomic mass of O is 15.9994 g/mol For Al, 1 mol x 26.9815 g/mol = 26.9815 g/mol For N, 3 moles x 14.0067 g/mol = 42.0201 g/mol For O, 9 moles x 15.9994 g/mol = 143.9946 g/mol For the entire molecule: 26.9815 + 42.0201 + 143.9946 = 212.9962 g/mol The molar mass of aluminum nitrate is 212.996 g/mol Note: The decimal places of the answer are consistent with the decimal places in the atomic masses, your periodic table might be less precise (less decimals).
72. What is a hydrate? A compound that contains water
73. How do you name a hydrate? To name a hydrate, you name the molecule, then add the Greek prefix corresponding to how many water molecules are attached and end with "hydrate". e.g. CuSO4 *5H2O is copper (II) sulphate pentahydrate.
74. Convert 2.5 mol of KClO3 to grams. MM (KClO3) = 122.55 g/mol (the combined mass of 1 K, 1 Cl and 3 O atoms) 2.5 mol x 122.55 g/mol = 306.375 g
75. Calculate how many moles are in 17.0 g of H2O2 moles = mass / molar mass = 17.0 g / 34.0146 g/mol = 0.500 mol
76. What is the mass of one molecule of H2O?
77. What is the law of definite proportions/ constant composition A chemical compound always contains exactly the same proportion of elements by mass. I.e. the proportion of the mass of the elements in a compound always stays the same
78. Calculate the percentage composition (by mass) of Al2O3. MM(Al2O3) = 2(27 g/mol) + 3(16 g/mol) = 102 g/mol % Al = 2(27 g/mol)/102 g/mol x 100% = 52.9% % O = 3(16 g/mol)/102 g/mol = 47.1% So Al2SO3 is 52.9% aluminum and 47.1% oxygen.
79. 13.0 g of tin is burned in the presence of oxygen to form 16.5 g of tin (IV) oxide. Which of the following represents the percentage composition of tin by mass in this compound? 33.5% 44.1% 78.8% 85.1% 78.8%
80. What does the empirical formula indicate? It indicates the simplest ratio in which the different atoms are combined.
81. A sample of calcium chloride contains 1.82 g of calcium and 3.23 g of chlorine. What is the empirical formula for the compound? Ca: 1.82 g/40.1 g/mol = 0.0454 mol Cl: 3.23 g/35.5 g/mol = 0.0910 mol mole ratio = Cl:Ca = 0.0910 mol:0.0454 mol = 2:1 So there are 2 mol of Cl for every 1 mol of Ca The empirical formula is CaCl2.
82. The elemental analysis of an unknown organic compound returns the following data: %C = 64.6% %H = 10.8% %O = 24.6% What is the empirical formula for this compound? C: 64.6 g / 12.001 g/mol = 5.38 mol C H: 10.8 g / 1.008 g/mol = 10.7 mol H O: 24.6 g / 16.00 g/mol = 1.54 mol O Divide the number of moles by the smallest number of moles to determine the relative ratios of the elements. C:H:O = 5.38 / 1.54 : 10.7 / 1.54 : 1.54 / 1.54 = 3.49:6.95:1.00 This gives the formula C3.49H6.95O1.00 Remember that elements only combine in whole number ratios. If the ratios are close to whole numbers then we know the empirical formula. If they are not, then you must multiply the ratios by a whole number until all are relatively close to an integer value. Here, we multiply the above formula by 2. Therefore, the empirical formula is C6.98H13.9O2.00 You can round this off to C7H14O2
83. What does the molecular formula indicate? How is it determined? The number of atoms of each element in a molecule Using the empirical formula and the molar mass.
84. Hydrogen peroxide is made of 5.03% hydrogen and 79.87% oxygen. Its molar mass is 34.01 g/mol. Find its molecular formula. Hydrogen peroxide is made of 5.03% hydrogen and 79.87% oxygen. Its molar mass is 34.01 g/mol. Find its molecular formula. First, you need to find the empirical formula: Percentages are given, so you can assume that you are working with a 100 g sample that is 5.03 g of hydrogen and 79.87 g of oxygen. H: 5.03 g/1.0079 g/mol = 4.99 mol O: 79.87 g/15.9994 g/mol = 4.99 mol mole ratio = H:O = 4.99 mol:4.99 mol = 1:1 So there is 1 mol of H for each mole of O. The empirical formula is HO. Now, you can find the molecular formula: MM(HO) = 17.0073 g / mol MM(hydrogen peroxide) = 34.01 g/mol MM(hydrogen peroxide)/MM(HO) = 34.01 g/mol / 17.0073 g/mo = 2 the molecular formula of hydrogen peroxide is H2O2.
85. If 4.04 g of nitrogen combine with 11.46 g of oxygen to produce a compound with a molar mass of 108.0 g/mol, what is the molecular formula of this compound? N: 4.04 g N2 x 1 mol/28.013 g = 0.144 mol O: 11.46 g O2 x 1 mol/31.999 g = 0.358 mol Divide by lowest amount to get simplest ratio: N: 0.144 mol / 0.144 mol = 1 O: 0.358 mol / 0.144 mol = 2.5 Therefore, multiply by 2 to give 2N and 5O (can’t have 2.5 atoms of O) This gives an empirical formula of N2O5 and has a mass of 108.01 g/mol This matches the molar mass given, so the molecular formula is N2O5
86. What does quantitative chemical analysis determine? The quantity of a substance in a sample
87. What is Stoichiometry the study of? What is an analogy to this? of the amount of reactants and products involved in chemical reactions. It is like considering a chemical reaction as a recipe. For example, to build a car, you need a body (B), an engine (E) and tires (T).
88. How many moles of product could 10 moles of nitrogen produce? N2 + 3H2 → 2NH3 1:3:2 ratio of moles 10 mol of N2 would take 30 mol of H2 and would produce 20 mol of NH3
89. How many moles of oxygen are produced by the decomposition of 2.8 mol of potassium chlorate? 2KClO3 → 2KCl + 3O2 2:2:3 (simplify ratio) 3 mol O2/ 2 mol KCLO3 = 1.5 mol O2/1 mol KCLO3 1.5 mol O2 / 1 mol KClO3 x 2.8 mol KCLO3 = 3.4 mol O2
90. Calculate the number of moles of silver nitrate that are needed in order to completely react with 7.1 mol of copper. Cl2 + 2Na --> 2NaCl 7.1 mol*1 = 7.1 mol Cu 7.1 mol* 2 = 14.2 mol AgNO3
91. Propane is a gas that is commonly used in BBQs. Its formula is C3H8. Calculate the mass of water that is produced by the combustion of 13.8 mol of propane. C3H8 + 5O2 --> 3CO2 + 4H2O 13. 8 mol propane / 1 mol propane x 4 mol water = 13.8 mol propane x (4 mol water/ 1 mol propane) = 55.2 mol 55.2 mol popane x MM[propane] = 55.2 mol x 44.096 g/mol = 2434.11 g
92. How many moles of chlorine are required to react completely with 48.6 g of sodium to produce sodium chloride? 2NA + Cl2 --> 2NaCL moles(Na) = mass(Na)/MM[Na] = 48.6g / 58.443 g/mol = 0.832 mol 0.832 mol propane x 1 mol chlorine / 2 mol sodium = 0.416 mol
93. Calculate how many grams of ammonia can be produced when 206.9 g of nitrogen reacts with hydrogen. N2 + 3H2 --> 2NH3 moles(nitrogen) = 206.9 g / 28.013 g/mol = 7. 39 mol 7.39 mol N2 x 2 mol NH3 / 1 mol N2 = 14.78 mol NH3 14.78 mol NH3 x MM[NH3] = 24.78 mol x 17.03 g / mol = 251.709 g
94. What is the theoretical yield? The maximum amount of product that could be formed from given amounts of reactants.
95. What is the actual yield? the amount of product that actually forms when the reaction is carried out in the laboratory
95. What is the period yield? the ratio of the actual yield to the theoretical yield expressed as a percentage
96. organic chemist reacts 10 g of CH4 with excess Cl2. She obtained 10 g of CH3Cl and some H2. a) What is the theoretical yield? b) What is her percentage yield? 2CH4 + Cl2 --> 2CH3Cl + H2 percentage yield = (actual yield / theoretical yield) x 100% = 10 g / 31.47 g = 31.78%
97. 36 g of ethyl ethanoate (CH3CO2C2H5) are obtained from 23 g of ethanol (C2H5OH) using the following equation: C2H5OH + CH3CO2H --> CH3CO2C2H5 + H2O What is the % yield? percentage yield = (actual yield / theoretical yield) x 100% = 36 g / 43.987 g = 81.84%
98. What is the limit reagent/reactant? What does it mean when a reactant is in excess? The reactant that is entirely used up before the other reactants (so the reaction stops). This limit how much product we get. The reactant that is not completely used up in a reaction and which there is EXCESS of. This reactant limits the maximum yield of the product.
99. Methane, CH4, burns in oxygen to give carbon dioxide and water according to the following equation: CH4 + 2O2 --> CO2 + 2H2O In an experiment, a mixture of 0.25 mol of methane is burned in 1.25 mol of oxygen in a sealed steel vessel. Find the limiting reactant. You can recognize a limiting reactant problem because there is more than one amount that is given in the question. (2 values given in question) Convert all of the reactants to the SAME product (pick any product you choose.) 0.25 mol CH4 * 1 mol CO2/1 mol CH4 = 0.35 mol CO2 1.25 mol O2 * 2 mol CO2 / 2 mol O2 = 0.625 mol CO2 The lowest answer corresponds to the substance that is the limiting reagent. CH4 is the limiting reagent since it produces the least amount of CO2 The other reactant(s) are in excess. O2 is in excess; there is some left over in the end.
100. What is the solubility of a substance? It is the mass required to make a saturated solution in a given quantity of water at a certain temperature.
101. The solubility of a substance can be affected by: The nature of the substances For example, ionic compounds and hydrates dissolve in aqueous solutions. The polarity of the substances For example, polar substances dissolve in polar solvents. The temperature Some substances only dissolve above certain temperatures. The pressure Some substances only dissolve when under pressure.
102. The rate at which a substance dissolves is affected by: 1. Particle size Finely divided substances have more surface area and dissolve more rapidly. 2. Motion Stirring or shaking brings more solvent into contact with more solute particles, increasing solubility. 3. Temperature The solubility of most solids increases with temperature. The solubility of gases decreases with temperature.
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