CHEM103/ CHEM 103 Module 4 – General Chemistry I with Lab | Portage Learning | Latest Exam Questions & Answers | Verified Study Material | Grade A

CHEM103/ CHEM 103 Module 4 – General Chemistry I with Lab | Portage Learning | 2026 2027 Latest Exam Questions & Answers | Verified Study Material | Grade A 2026 / 2027 Academic Year Q: Avogadro's number Answer 6.022 x 10^23 atoms = 1 mole Q: 1 u = ___ g Answer 1.661 x 10 ^-24 g Q: formula mass Answer the sum of the average atomic masses of each atom represented in the chemical formula and is expressed in atomic mass units. --The formula mass of a covalent compound is also called the molecular mass. Q: The chemical identity of a substance is defined by Answer the types and relative numbers of atoms composing its fundamental entities (molecules in the case of covalent compounds, ions in the case of ionic compounds). Q: A compound's percent composition provides Answer the mass percentage of each element in the compound. Q: calculate the formula mass of a substance by Answer summing the average atomic masses of all the atoms represented in the substance's formula. Q: A mole is defined as Answer the amount of substance containing the same number of discrete entities (such as atoms, molecules, and ions) as the number of atoms in a sample of pure 12-C weighing exactly 12 g Q: percent composition Answer the percentage by mass of each element in a compound i.e. mass X / mass compound x 100% Q: stoichiometry Answer refers to the quantitative relationships between amounts of reactants and products in a chemical reaction. Q: Combustion Answer a reaction in which an element or compound burns in air or oxygen --The combustion of compounds containing hydrogen and carbon (CxHy) will always produce two products: water (H2O) and carbon dioxide (CO2). --The same is true for the combustion of compounds containing hydrogen, carbon and oxygen (CxHyOz) Q: Chemical formulas provide the identities of the reactants and products involved in the chemical change, allowing classification of the reaction Q: Coefficients provide the Answer relative numbers of these chemical species, allowing a quantitative assessment of the relationships between the amounts of substances consumed and produced by the reaction. Q: stoichiometric factor Answer ratio of coefficients in a balanced chemical equation, used in computations relating amounts of reactants and products Q: Limiting Reactant Answer A reactant that is totally consumed during a chemical reaction, limits the extent of the reaction, and determines the amount of product. Q: theoretical yield Answer The amount of product that may be produced by a reaction under specified conditions, as calculated per the stoichiometry of an appropriate balanced chemical equation, is called the theoretical yield of the reaction Q: actual yield Answer the amount of product that forms when a reaction is carried out in the laboratory Q: percent yield Answer actual yield/theoretical yield x 100 Q: Mass percent Answer Mass % = Mass x / total mass times 100% (assume 1 mole of X) Q: Use mass percent to calculate molecular formula Answer Assume 100 g, not 1 mole Convert % X into g; ex. 64% N = 64 g of Nitrogen Convert to moles Put smaller quantity in the denominator; divide to find ratio of # mol X to # mol Y Q: To determine an empirical formula, you must Answer find the smallest whole-number ratio of atoms in a molecule. --If you begin with the mass of each element in the compound, you must first convert these masses to moles before determining the ratio. Q: A compound's percent composition provides the Answer mass percentage of each element in the compound, and it is often experimentally determined and used to derive the compound's empirical formula. Q: The empirical formula mass of a covalent compound may be compared to Answer the compound's molecular or molar mass to derive a molecular formula. Q: Combustion analysis can be used to Answer identify an unknown hydrocarbon because the identity of the products are known to be CO2 and H2O. Q: Empirical formulas are derived from experimentally measured element masses by Answer --Deriving the number of moles of each element from its mass --Dividing each element's molar amount by the smallest molar amount to yield subscripts for a tentative empirical formula --Multiplying all coefficients by an integer, if necessary, to ensure that the smallest whole number ratio of subscripts is obtained Q: Empirical formula Answer a formula with the lowest whole-number ratio of elements in a compound Q: Ionization Energy Answer Measures how much energy is needed to remove an electron from an atom or how difficult it is for an atom to form a positive ion. Q: Ionization Energy (Increase) Answer Property increases as you go L -- R across a horizontal row of elements b/c more energy is needed to remove an electron that's being attracted by a greater nuclear charge. Q: Ionization Energy (Decrease) Answer Property decreases as you go down a vertical column of element b/c the element are becoming larger and less is needed to remove an electron that's further away from the attracting nucleus. Q: Electronegativity Answer The attraction an atom has for its outer shell electron or how tightly it holds its valence electrons. Q: Electronegativity (Increase) Answer Property increases as you got L -- R across a horizontal row of elements and greater nuclear charge holds the outer shell electrons more tightly Q: Electronegativity (Decrease) Answer Property decreases as you go down a vertical column of elements b/c elements are becoming larger and the outer shell electrons are more distant from the attracting nucleus. Atomic Size Answer The distance from the center of the nucleus to the outer shell of an atom. Atomic Size (Increase) Answer representation of a molecule that uses chemical symbols to indicate the types of atoms followed by subscripts to show the actual number of atoms of each type in the molecule (CH4) or (C_6H_12O_6) Increases as you go down a vertical column of elements because the element have outer shells that are further away from the nucleus. Atomic Size (Decrease) Answer Decreases as you go L -- R across the horizontal row of elements because the outer shell is being attracted by a greater nuclear charge molecular formula Answer structural formula Answer gives the same information as its molecular formula (the types and numbers of atoms in the molecule) but also shows how the atoms are connected in the molecule Models Answer Ball and stick (geometric arrangement, not to scale) Space Filling (shows relative sizes) Coefficient vs Subscript Answer H = one H atom 2H = Two H atoms H_2 = one H_2 molecule 2H_2 = Two H_2 molecules Empirical Formula Answer Gives us the relative number of atoms in their whole number ratio (DOES NOT REFLECT THE STRUCTURE, true nature or anything about the compound itself) a chemical formula showing the ratio of elements in a compound rather than the total number of atoms Answer Ex: Acetic Acid = CH_3COO = HCH_3COO = HC_2H_3O_2 = C_2H_4_O2 The Empirical Formula is CH_2_O reducted from the final most consolidated form *NOTE: Molecular Formula is ALWAYS a whole number multiple of the empirical formula Isomer Answer compounds with the same chemical formula but different molecular structures Formula Mass Answer the sum of the average atomic masses (in amu) of all the atoms represented in the formula of any molecule, formula unit, or ion (the substance's formula) Formula Mass for Covalent Substances Covalent Formula = Molecular Formula Formula Mass = Molecular Mass Element Quantity * Average Atomic Mass = subtotal (amu) Mole The mole provides a link between an easily measured macroscopic property, bulk mass, and ROUNDING: Same sig figs as the least decimals for addition/substraction Formula Mass for Ionic Substances Ionic Formulas DO NOT equal molecular formulas (ionic formula gives the lowest whole number ration of ions) the formula for an ionic compound does not represent the composition of a discrete molecule, so it may not correctly be referred to as the "molecular mass". Ex: Al_2(SO_4)_3 = 2xAl + 3xS + 12xO amu an extremely important fundamental property, number of atoms, molecules, and so forth. A mole of substance is that amount in which there are 6.022 × 10^23 discrete entities (atoms or molecules) Avogadro's number (NA) experimentally determined value of the number of entities comprising 1 mole of substance, equal to 6.022 × 10^23 mol−1 Molar Mass the mass in grams of one mole of a substance (g/mol) - Differs for elements and substances - Numerically equivalen in grams to its atomic or formula mass in amu - Enables calculations between moles, molecules, atoms and mass - Average Atomic Mass C = 12.01 amu - Molar Mass (g/mol) = 12.01 - Atoms/Mole = 6.022 x 10^23 Percent Composition - Chemical formulas represent elemental make up of a compound, percent composition gives us the relative abundance of any given element in known compound formulas - Must be determined experimentally - % = mass of element / mass of compound *100% Determining Empirical Formulas Chemical formulas represent relative numbers, not masses, of atoms Therefore, to derive numbers of atoms from mass, we must convert to moles Moles can be used to compute who number ratios to derive the empirical formula These are NOT molecular formulas - can ONLY give Empirical Formula Empirical Formula Steps 1. Convert mass to moles 2. Divide each element's molar amount by the smallest molar amount found in step 1 3. Multiply all coefficients by an integer, if necessary, to get to smallest whole-number ratio Empirical Formula From Percent Comp % = mass of element (g) (mass of element / mass of compound) 100 = (mass of element (g) / 100 g compound) 100 Deriving the Molecular Formula - must know molecular / molar mass which is experimentally determined - always a muliple of the empirical fomula, and molecular mass similarly is a multiple of the empirical formula mass - Empirical Formula Mass = sum of average atomic masses of all atoms represented in formula = molecular or molar mass (amu or g/mol) / empirical formula mass (amu or g/mol) = n formula units/molecule Solvent In a solution, the substance in which the solute dissolves (or the medium in which the other components are dispersed) Solution A homogeneous mixture of two or more substances Aqueous Solution a solution in which water is the solvent Dilute small amount of solute Concentrated relatively high concentration of solute Solute the substance that is dissolved typically present at lower concentration than the solvent Concentration Relative amount of a given solution component Molarity (M) - concetration unit for solutions - expressed as the number of moles of solute dissolved in exactly 1 liter of solution - M = mol of solute / L of solution Dilution the process whereby the concentration of a solution is lessened by the addition of solvent MOLARITY (M) * (L) of Solution = mol of solute (n) n= ML Before dilution: n1 = M1*L1 After Dilution: n2 = M2 * L2 NOTE: mole concertration does not change, dilute does not change the amount of solute in the solution (n1 = n2) M1 L1 = M2 L2 Dilution Equation M1 L1 = M2 L2 where C1 V1 = C2 V2 C = concentration V = volume mass percentage ratio of solute-to-solution mass expressed as a percentage "percent mass" "percent weight" "weight / weight percent" symbol: %, % mass, % weight, and (w/w)% Volume Percentage Ratio of the volume of a liquid solute to the solution total VP = volume solute / volume solution * 100% Symbol: %vol or (v/v)% Mass-Volume Percentage Ratio of a solute's mass to the solution's volume expressed as % Symbol: % mass-volume, (m/v)% PPM & PPB Used for very low solute concentations how many pyruvic acids can be made from 2 sucrose molecules in glycolysis? 8 Can be based on mass, volume, or mixed units or numbers of atoms / molecules % = pph = parts per hundred ppm = parts per million ppb = parts per billion what % of energy in glucose is saved in glycolysis? 2% how much CO2 is produced from 2 glucose molecules in human glycolysis only? 0 what steps in glycolysis represents substrate level phosphorylation? step #7 & #10 what step in glycolysis is oxidation? step #6 what step in glycolysis is dehydration? step #9 why is phosphatase found only in the liver? glycogen in the liver must provide glucose for the entire body which reaction in the connecting step to Krebs cycle is endothermic? synthesis what type of functional group is found at the very end of a coenzyme A molecule? thioalcohol what is the high energy bond in acetyl - CoA? thio ester what reaction in the connecting step to Krebs cycle is exothermic? oxidation anaerobic conditions - without oxygen - humans - lactic acid formed in muscles - yeast - fermentation and ethanol produced aerobic conditions - has oxygen - krebs cycle - electron transport phosphate highest energy compound, cannot move through protein channel endothermic reaction - needs energy - putting phosphate on enzyme #1 in glycolysis glycogen phosphorylase enzyme #2 in glycolysis phosphatase (liver only) substrate-level phosphorylation making of ATP without O2 or electron transport staring points of gluconeogenesis - lactic acid - glycerol - some amino acids phosphatase - removes phosphate group - found ONLY in the liver bc provides glucose to entire body - converts glucose 6 phosphate to glucose when glucagon affects liver cell, a phosphate is attached to both glycogen synthetase and glycogen phosphorylase, which enzyme is activated? glycogen phosphorylase Which cells need insulin for glucose entry? muscle cells, liver, adipose If glycogen synthetase were allosteric, what effect would ATP have on it? activate what happens to most of the glucose 6 phosphate in liver vs muscle tissue? - in muscle it is used for energy, in liver it is converted to glucose to be transported by the blood - they can both be converted to glycogen if not needed what can not be converted back to glucose 1 phosphate fructose 1,6 bisphosphate because step #3 is irreversible proteins glucagon, insulin, lactic acid dehydrogenase, and amino acids Polysaccharides glycogen, starch, cellulose can move through cell membrane glucose and cortisol can stimulate fatty acid synthesis from acetyl-CoA insulin can stimulate the immediate conversion of glycogen to glucose 1 phosphate in the liver glucagon and epinephrine Fructose-1,6-bisphosphatase produces most ATP in glycolysis can stimulate the conversion of certain amino acids to glucose in gluconeogenesis cortisol Anabolism Metabolic pathways that construct molecules, requiring energy. Catabolism Metabolic pathways that break down molecules, releasing energy. glucose simple sugar, produces least ATP in glycolysis in anaerobic exercise, the pH of the muscles will ... decrease processes that need a lot of ATP muscle activity and synthesizing protein from amino acids (active transport, all anabolic reactions) starting point of glycolysis in a red blood cell glucose starting point of glycolysis in a muscle cell glycogen purpose of converting pyruvic acid to lactic acid is to regenerate NAD cannot move through cell membrane - glycogen - glucose-1-phosphate - protein hormones - epinephrine - polypeptides cAMP secondary messenger, used for protein hormones Digestion is the process of breaking down food into molecules the body can use, hydrolysis diabetes - occurs when there are not enough insulin receptor sites - will occur when not enough insulin is secreted b the pancreas - kidney will excrete large amounts of water in order to remove excess sugar from the blood covalent modification when a phosphate is added to an enzyme to either activate or deactivate it Glucagon A protein hormone secreted by pancreatic endocrine cells that raises blood glucose levels; an antagonistic hormone to insulin - famine hormone Where is galactose converted to glucose? liver epinephrine A substance secreted from the adrenal glands in response to a threat, strenuous exercise or stress - reaches receptor sites on muscle/liver and stimulates glycogenolysis where does digestion start? carbohydrates - mouth proteins - stomach lipids - small intestine the enzyme in step 4 of the Krebs cycle is an allosteric enzyme with sites for ATP, ADP and NADH, which will active the enzyme? ADP, needs more what produces the most CO2? Krebs cycle electron transport - uses electrons from the Krebs cycle to change ADP to ATP - uses O2 - converts FADH2 to FAD - oxidative phosphorylation Produce the most ATP per glucose glucose metabolism in a typical cell under aerobic conditions high energy more hydrogens and less oxygens percent of energy stored as ATP in aerobic oxidation of glucose 40% NADH highest energy compound mitochondria - a cell which must do a lot of work will have more than one that doesn't work - a cell can produce more mitochondria if it needs to do more work blood glucose primary source of energy in red blood cells and brain during healthy eating ketone bodies the product of the incomplete breakdown of fat when glucose is not available in the cells - primary source of energy in the brain during starvation - too much in blood can cause ketosis - since 2/3 ketone bodies are acids it can lead to acidosis - synthesized by liver fatty acids long carbon chains that make up most lipids - primary source of energy in resting muscle and liver glycogen primary source of energy in muscle during strenuous activity if no oxygen present, which processes occur? Krebs cycle, glycolysis, and glycogenolysis Pyruvate to Acetyl CoA 1. decarboxylation 2. oxidation 3. synthesis how many COs are produced from the complete aerobic oxidation of 4 acetyl-CoA 8 how many ATP are produced from anaerobic oxidation of 9 glucose molecules? 18 complete aerobic oxidation of 5 pyruvic kids will produce how many CO2? 15 For 6 glucose molecules going to pyruvic acid, how many NAD molecules are used up? 12 fermentation Process by which cells release energy in the absence of oxygen - pyruvic acid to ethanol metabolism of fatty acids - long chains are broken down into groups of carbons body temperature energy from glucose metabolism is not stored as ATP and is used for maintaining step #1 Krebs cycle - enzyme = synthetase - substrates - acetyl CoA and oxaloacetic acid - product - citric acid ketone body that is not acidic acetone