“A WINNER knows how much he has to LEARN, even when he is considered an EXPERT by others. A LOSER wants to be considered an EXPERT by others before he has learned enough to know how LITTLE he knows.” CHEMISTRY - From egyptian kēme, meaning “earth” - the science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions. Hypothesis – A statement or idea that describes or attempts to explain observable information. Experiment – Is a controlled testing of the properties of a substance or system through carefully recorded measurements. Theory – The result of thorough testing and confirmation of a hypothesis. A theory predicts the outcome of new testing based on past experimental data. Law – A hypothesis or theory that is tested time after time with the same resulting data and thought to be without exception 1. Who is said to be the founder of the scientific method? A. Alexander Fleming B. Joseph Priestly C. Galileo Galilei D. Antoine Lavoisier 2. In the universe, it is anything that occupies space and has mass. A. Matter B. Isotope C. Atom D. Solid Matter - anything that occupies space and has mass (i.e., anything that has density). It commonly exists in three phases: solid, liquid, and gas. 3. Electron came from the greek word: A. Helios B. Elektra C. Amber D. Volta 4. Which of the following falls under fluids? A. gas B. solid C. liquid. D. both a & c. 5. The state of matter which occupies the whole space available is A. gas B. solid C. liquid D. both a & c. 6. It is a property of matter which can be measured by changing the identity and composition of a substance. A. Chemical B. extensive C. physical D. extrinsic 2/2/2020 13 7. Which of the following is not an extensive property? A. Energy B. Weight C. Boiling point D. Length THE ATOM Atom is the basic building block of matter. It is the smallest particle of element. An ELEMENT is a fundamental type of matter in which all of the atoms in the material are the same. The atomic number of an element is the number of protons that is contained in the nucleus of each of its atoms. Mass number or atomic weight is the sum of the number of protons and neutrons in the nucleus of the atom. A compound is a substance with a particular ratio of atoms of particular chemical elements which determines its composition, and a particular organization which determines chemical properties. The standard nomenclature of chemical substances is set by the International Union of Pure and Applied Chemistry (IUPAC). 8. What do you call chemically identical atoms of the same element but with different numbers of neutrons and different mass numbers. A. Isotones B. Isobars C. Isotopes D. homogenous 9. Tritium has A. 1 electron and 1 proton B. 1 proton and 1 neutron C. 1 proton and 2 neutron D. 2 proton and 1 neutron Protium – most common hydrogen isotope Deuterium – 1 neutron, 1 proton - non radioactive, -“heavy hydrogen” Tritium – 2 neutrons, 1 proton radioactive Hydrogen is the only element that has different names for its isotopes in common use today. 10. What is the most abundant element in the universe? A. nitrogen B. hydrogen C. oxygen D. helium 11. What is the most abundant element in the Earth’s atmosphere? A. nitrogen B. hydrogen C. oxygen D. helium 12. The net electrical charge of an atom under normal state is: A. negative B. positive C. neutral D. infinite 13. A substance that cannot be decomposed into simpler substances by ordinary chemical reactions A. Compound B. Mixture C. Element D. Homogenous 14. The subdivision of an element that can take part in a chemical reaction A. Element B. Hydrogen C. Electron D. Atom 15. The sub-atomic part consisting of neutrons and protons is known as A. Nuclear fusion B. Nucleons C. Neurons D. Neutron-proton spatial formation IV. ATOMIC NUMBER AND MASS NUMBER The atomic number of an element is the number of protons that is contained in the nucleus of each of its atoms. Mass number or atomic weight is the sum of the number of protons and neutrons in the nucleus of the atom. 16. The no. of protons in the nucleus on an atom A. Atomic number B. Mass number C. Atomic mass D. Atomic mass unit 17. The no. of protons and neutrons in the nucleus of an atom A. Atomic number B. Mass number C. Atomic mass D. Atomic mass unit 18. 1 amu is approximately equal to A. 6.23 x 10 ^ -27 kg B. 2.36 x 10 ^ -27 kg C. 3.62 x 10 ^ -27 kg D. 1.66 x 10 ^ -27 kg 19. The group of elements that do not normally combine with other elements to form compounds A. Alkali Metals B. Chalcogens C. Inert gases or noble gases D. Halogens 20. What do you call the electrons in the outermost orbitals? A. Valence electrons B. super electrons C. holes D. active electrons 21. Calculate the mass of the product of reaction of 6.54 g of zinc with 3.21 g of sulfur. A. 21 g B. 3.33 g C. 9.75 g D. 10.15 g 22. Calculate the mass of the oxygen that reacts with 1.24 g of methane (natural gas) to form 3.41 g of carbon dioxide and 2.79 g of water. A. 7.38 g B. 1.86 g C. 0.62 g D. 4.96 g ATOMIC MASS The atomic mass (or atomic weight) of an element is the average of the element’s isotopic masses. Atomic mass m1p1 m2p 2 m3p3 ... Where mn mass of isotopes 1,2,3... pn percent abundance of isotopes 1,2,3... 23. Calculate the atomic mass of an element if 60.4% of the atoms have a mass of 68.9257 amu and the rest have a mass of 70.9249 amu. A. 67.9 amu B. 69.7 amu C. 79.6 amu D. 97.6 amu 24. Calculate the atomic mass of an element if 60.4% of the atoms have a mass of 68.9257 amu and the rest have a mass of 70.9249 amu. A. 79.6 amu B. 67.9 amu C. 96.7 amu D. 69.7 amu Practice Problem: Calculate the percentage of bromine atoms that have a mass of 78.9183 amu and the percentage that have a mass of 80.9163 amu. The atomic mass of bromine is 79.909 amu, and theses are the only two naturally occurring isotopes. A. 35.3%, 64.7% C. 50.4%, 49.6% B. 47.5% , 52.5% D. 63.2%, 36.8% FORMULA MASS The formula mass (or formula weight) is the sum of the masses of all atoms in a given formula. THE MOLE A mole is the amount of pure substance containing the same number of chemical units, as there are atoms in exactly 12 grams of carbon-12. AVOGADRO’S NUMBER One mole refers to Avogadro’s number of particles of anything: 23 NA 6.02 10 MOLE – MASS CONVERSIONS The formula for calculating among mass, gramformula mass (also known as molar mass), and the number of moles: m n FM Where: n = number of moles m = mass of the substance in grams M= molar mass in grams per mole MOLE – NUMBERS OF PARTICLES CONVERSION Conversion factor: 1 mole 6.02 1023 particles • EXAMPLE: How many particles are in 2.00 moles of SO2? Ans. 1.2 x 1024 particles 25. Calculate the formula mass of (NH4)2HPO4 (one type of fertilizer). A. 125 amu B. 132 amu C. 110 amu D. 148 amu 26. Calculate the number of moles of Al atoms in 5.75 x 1024 Al atoms. A. 19.1 mol Al atoms B. 9.55 mol Al atoms C. 4.77 mol Al atoms D. 14.3 mol Al atoms 27. Calculate the number of moles of H2 molecules in 5.75 x 1024 H2 molecules. A. 19.1 mol H2 molecules B. 9.55 mol H2 molecules C. 4.77 mol H2 molecules D. 14.3 mol H2 molecules 28. Calculate the number of molecules in 30 g NH3. A. 1.06 x 1024 molecules B. 3.08 x 1024 molecules C. 1.06 x 1023 molecules D. 3.08 x 1023 molecues 29. In a 5.00-g sample of carbon, how many of the atoms have a mass of 12.01 amu? A. None B. 2.507 x 1023 molecules C. 2.507 x 1024 molecules D. 1.44 x 1024 molecules EMPIRICAL FORMULA An empirical formula is a formula that gives the simplest wholenumber ratio of atoms in a compound. Steps for Determining an Empirical Formula Start with the number of grams of each element, given in the problem. If percentages are given, assume that the total mass is 100 grams so that the mass of each element = the percent given. 2. Convert the mass of each element to moles using the molar mass from the periodic table. 3. Divide each mole value by the smallest number of moles calculated. Round to the nearest whole number. This is the mole ratio of the elements and is represented by subscripts in the empirical formula. (If one of the numbers is 1.5, you would multiply each number by 2, and get a whole number of 3). 30. Calculate the empirical formula of “hypo,” used in photographic development, consisting of 29.1% Na, 40.5% S, and 30.4% O. A. NaS2O2 B. NaS2O3 C. Na2S4O3 D. Na2S2O3 MOLECULAR FORMULA Once the empirical formula is found, the molecular formula for a compound can be determined if the molar mass of the compound is known. Steps for Determining molecular Formula 1. Find the empirical formula 2. Find the mass of the empirical unit. 3. Divide the molecular mass of the compound by the mass of the empirical formula. 4. Multiply all the atoms (subscripts) of the empirical formula by this ratio to find the molecular formula. 31. Calculate the molecular formula of a compound with molar mass 104 g/mol composed of 92.3% carbon and 7.7% hydrogen. A. C8H8 B. C7H14 C. C2H3 D. C7H8 CHEMICAL REACTION A chemical reaction is a process in which a substance or a combination of substances undergo a change in appearance or properties, and further transform into a different substance or a combination of new substances. CLASSIFICATION OF CHEMICAL REACTIONS DIRECT COMBINATION OR SYNTHESIS A B AB DECOMPOSITION AB A B SINGLE – REPLACEMENT REACTIONS A BC AC B Double – Replacement Reactions AB CD AD CB 32. The reaction Na2O + H2O 2NaOH illustrates a A. Synthesis Reaction B. Metathesis Reaction C. Single Replacement Reaction D. Decomposition Reaction 33. The reaction Ba(OH)2 + 2CuCNS Ba(CNS)2 + 2CuOH is an example of A. Synthesis Reaction B. Metathesis Reaction C. Single Replacement Reaction D. Decomposition Reaction 34. The decomposition of a given compound can be carried out A. by heating the compound B. by passing the electric current while heating C. by passing the electric current D. either by passing electric current or heating I. UNITS OF CONCENTRATION MOLE FRACTION The number of moles of solute divided by the number of moles of solvent and all solutes. XA nA nA nB or XB nB nA nB NORMALITY The number of gram equivalent weights of solute per liter. A solution is “ normal” if there is exactly one gram equivalent weight per liter. nORMALITY Equivalent weight in grams Vsolution in liters MOLARITY Molarity (M) is defined as the number of moles of solute dissolved in 1 liter of solution. In other words, molarity is a ratio between number of moles of solute and the number of liters of solution. nsolute M Vsolution ( L ) FORMALITY The number of gram formula weights (i.e., molecular weights in grams) per liter of solution. FORMALI TY Formula weight in grams Vsolution in liters MOLALITY Molality (m) is defined as the number of moles of solute dissolved in 1 kg of solvent. In other words molality is the ratio between the number of moles of solute and the mass of the solvent expressed in kilograms. m nsolute kg solvent mass solute MM solute kg solvent PERCENT OF VOLUME Percent of volume refers to the number of millilitres of solute dissolved in 100 ml of solution. volume solute % volume x100 volume solution DILUTION Dilution is the process of adding solvent (usually water) to a concentrated solution to achieve a solution of the desired concentration. When we dilute a solution, we do not change the number of moles of solute present, we simply add more solvent. Thus, Molesofsolute afterdi luti on=Molesofsolute before di luti on nafter nbefore MV after MV before 35. Calculate the molarity of a 250-mL solution containing 80.0 mmol of solute. A. 0.567 M B. 0.320 M C. 0.118 M D. 0.235 M 36. Calculate the number of moles of solute required to make 50.00 mL of 1.500 M solution A. 0.025 mol B. 0.75 mol C. 0.075 mol D. 0.25 mol 37. Calculate the molarity of a solution after 1.70 L of 2.06 M solution is diluted to 2.50 L. A. 1.20 M B. 2.10 M C. 1.50 M D. 1.40 M 38. Calculate the mole fraction of a solution of 0.015 mol of NaCl in 50.0 g of water if the solution has a density of 1.02 g/mL. A. 0.00536 B. 0.0536 C. 0.536 D. 0.000536 39. Calculate the molality of an alcohol in aqueous solution if the mole fraction of the alcohol is 0.150. A. 3.60 m alcohol B. 5.40 m alcohol C. 9.80 m alcohol D. 10.12 m alcohol ACIDS AND BASES ACIDS Acid is any compound that dissociates H+ ions into water . Acids with 1,2, and 3 ionizable hydrogen atoms are called monoprotic, diprotic, and triprotic acids, respectively. Properties of Acids: 1. 2. 3. 4. 5. 6. 7. Acid conducts electricity in aqueous solutions Acids have a sour taste Acids turn blue litmus paper to red Acids have pH between 0 and 7 Acids neutralizes bases Acids react with active metals to form hydrogen Acids react with oxides and hydroxides to form salts and water pH Equation: 1 pH log H For a partially ionized compound, X, in a solution of known molarity, M, the ionic concentration is: X fraction ionized M BASES Base is any compound that dissociates OH- ions into water. Bases with 1, 2, and 3 replaceable hydroxide ions are called monohydroxic, dihydroxic, and trihydroxic bases, respectively. Properties of Basis: 1. 2. 3. 4. 5. Bases conduct electricity in aqueous solutions Bases have bitter taste Bases turn red litmus paper to blue Bases have pH between 7 and 14 Bases neutralize acids, forming salts and water pOH Equation: 1 pOH log OH pH and pOH Relationship: pH pOH 14 40. Battery acid is the common name for A. formic acid B. hydrochloric acid C. nitric acid D. sulfuric acid 41. When one element causes the oxidation of another element, it is A. oxidized B. an acid C. reduced D. a base 42. According to the Bronsted Theory, an acid is A. a proton donor B. a proton acceptor C. an electron donor D. an electron acceptor 43. The pH of an acid solution is A. 3 B. 7 C. 9 D. 10 44. The pH of a solution with a hydrogen ion concentration of 1 x 103 is A. +3 B. -3 C. ±3 D. +11 45. The pH concentration of a solution that has a hydroxide ion concentration of 1 x 10-4 mol/L is A. 4 B. -4 C. 10 D. -10 46. A 10-6 M HCl solution is diluted to 100 times. The pH of the diluted solution would be A. between 6 to 7 B. between 7 to 8 C. equal to 7 D. equal to 10 47. A substance which can act both an acid and a base is: A. allotropic B. amphoteric C. isotopic D. amorphous
