Presentation on theme: "Mass Relationship in Chemical Reaction"— Presentation transcript:
1 Mass Relationship in Chemical Reaction CHEMISTRY - DACS 1232Fakulti Kejuruteraan Mekanikal, UTeMLecturer:IMRAN SYAKIR BIN MOHAMADMOHD HAIZAL BIN MOHD HUSINNONA MERRY MERPATI MITANMass Relationship in Chemical ReactionChapter 3
2 Atomic mass is the mass of an atom in atomic mass units (amu) By definition:1 atom 12C “weighs” 12 amuOn this scale1H = amu16O = amu
3 Average atomic mass of lithium: 3LiNatural lithium is:7.42% 6Li (6.015 amu)92.58% 7Li (7.016 amu)Average atomic mass of lithium:7.42 x x 7.016100= amu
5 Dozen = 12 Pair = 2 The mole (mol) is the amount of a substance that Mole, Molar Mass & NADozen = 12Pair = 2The mole (mol) is the amount of a substance thatcontains as many elementary entities as thereare atoms in exactly grams of 12C1 mol = NA = x 1023Avogadro’s number (NA)
6 atomic mass (amu) = molar mass (grams) Molar mass is the mass of 1 mole of in gramsatoms1 mole 12C atoms = x 1023 atoms = g1 12C atom = amu1 mole 12C atoms = g 12C1 mole lithium atoms = g of LiFor any elementatomic mass (amu) = molar mass (grams)
8 Do You Understand Molar Mass? How many atoms are in g of potassium (K) ?
9 molecular mass (amu) = molar mass (grams) Molecular mass (or molecular weight) is the sum ofthe atomic masses (in amu) in a molecule.SO21S32.07 amu2O+ 2 x amuSO264.07 amuFor any moleculemolecular mass (amu) = molar mass (grams)1 molecule SO2 = amu1 mole SO2 = g SO2
10 Do You Understand Molecular Mass? How many H atoms are in 72.5 g of C3H8O ?
11 C2H6O Percent Composition Percent composition of an element in a compound =n x molar mass of elementmolar mass of compoundx 100%n is the number of moles of the element in 1 mole of the compoundC2H6O
12 Determination of empirical formula shows the simplest whole-number ratio of the atoms in a substanceWhat are the empirical formula of the compounds with the following composition:a. 2.1 % H, 65.3 % O, 32.6 % Sb % Al, 79.8 % Cl
13 Molecular formulashows the exact number of atoms of each element in the smallest unitof a substanceThe molar mass of caffeine is g. The empirical formula is C4H5N2O. What is its molecular formula?
14 3 ways of representing the reaction of H2 with O2 to form H2O Chemical Reaction & EquationA process in which one or more substances is changed into one or more new substances is a chemical reactionA chemical equation uses chemical symbols to show what happens during a chemical reaction3 ways of representing the reaction of H with O2 to form H2Oreactantsproducts
15 How to “Read” Chemical Equations 2 Mg + O MgO2 atoms Mg + 1 molecule O2 makes 2 formula units MgO2 moles Mg + 1 mole O2 makes 2 moles MgO48.6 grams Mg grams O2 makes 80.6 g MgOIS NOT2 grams Mg + 1 gram O2 makes 2 g MgO
16 Balancing Chemical Equations Write the correct formula(s) for the reactants on the left side and the correct formula(s) for the product(s) on the right side of the equation.Ethane reacts with oxygen to form carbon dioxide and waterC2H6 + O2CO2 + H2OChange the numbers in front of the formulas (coefficients) to make the number of atoms of each element the same on both sides of the equation. Do not change the subscripts.2C2H6NOTC4H12
17 Balancing Chemical Equations Start by balancing those elements that appear in only one reactant and one product.C2H6 + O2CO2 + H2Ostart with C or H but not O1 carbonon right2 carbonon leftmultiply CO2 by 2C2H6 + O22CO2 + H2O6 hydrogenon left2 hydrogenon rightmultiply H2O by 3C2H6 + O22CO2 + 3H2O
18 Balancing Chemical Equations Balance those elements that appear in two or more reactants or products.multiply O2 by72C2H6 + O22CO2 + 3H2O2 oxygenon left4 oxygen(2x2)+ 3 oxygen(3x1)= 7 oxygenon rightC2H O22CO2 + 3H2O72remove fractionmultiply both sides by 22C2H6 + 7O24CO2 + 6H2O
19 Balancing Chemical Equations Check to make sure that you have the same number of each type of atom on both sides of the equation.2C2H6 + 7O24CO2 + 6H2O14 O (7 x 2)14 O (4 x 2 + 6)12 H (2 x 6)12 H (6 x 2)4 C (2 x 2)4 CReactantsProducts4 C12 H14 O
20 Mass Changes in Chemical Reactions Amounts of Reactants & ProductsMass Changes in Chemical ReactionsWrite balanced chemical equationConvert quantities of known substances into molesUse coefficients in balanced equation to calculate the number of moles of the sought quantityConvert moles of sought quantity into desired units
21 Methanol burns in air according to the equation 2CH3OH + 3O CO2 + 4H2OIf 209 g of methanol are used up in the combustion,what mass of water is produced?
22 Limiting Reagents6 red left over6 green used up
23 Do You Understand Limiting Reagents? In one process, 124 g of Al are reacted with 601 g of Fe2O32Al + Fe2O Al2O3 + 2FeCalculate the mass of Al2O3 formed.
24 Actual Yield x 100 % Yield = Theoretical Yield Reaction Yield Theoretical Yield is the amount of product that wouldresult if all the limiting reagent reacted.Actual Yield is the amount of product actually obtainedfrom a reaction.% Yield =Actual YieldTheoretical Yieldx 100
25 Example :If 3 gram C6H11Br is prepared by treating 3 gram C6H12 with5 gram Br2, What is the percent yield?
26 Reaction in Aqueous Solution A solution is a homogenous mixture of 2 or more substancesThe solute is(are) the substance(s) present in the smaller amount(s)The solvent is the substance present in the larger amountSolutionSolventSoluteSoft drink (l)Air (g)Soft Solder (s)
27 Solution Stoichiometry The concentration of a solution is the amount of solute present in a given quantity of solvent or solution.M = molarity =moles of soluteliters of solutionWhat mass of KI is required to make 500. mL ofa 2.80 M KI solution?
29 Dilution is the procedure for preparing a less concentrated solution from a more concentrated solution.DilutionAdd SolventMoles of solutebefore dilution (i)after dilution (f)=MiViMfVf=
30 How would you prepare 60.0 mL of 0.2 M HNO3 from a stock solution of 4.00 M HNO3?
31 Equivalence point – the point at which the reaction is complete TitrationsIn a titration a solution of accurately known concentration is added gradually added to another solution of unknown concentration until the chemical reaction between the two solutions is complete.Equivalence point – the point at which the reaction is completeIndicator – substance that changes color at (or near) theequivalence pointSlowly add baseto unknown acidUNTILthe indicatorchanges color
35 P2O5 is a drying agent because it reacts with water to form H3PO4 via the unbalancedequation:P2O5(s) + H2O(g) H3PO4(l)Balance the equation above.Give the chemical name of P2O5 and H3PO4Calculate the molecular weight of H3PO4.A sample of air that contains 47 mg of water is thoroughly dried by passing it over a bed of P2O5. Calculate the mass of H3PO4 produced.
36 Mustard gas (C4H8Cl2S) is a poisonous gas that was used in World War I and banned afterward. It causes general destruction of body tissues, resulting in the formation of large water blisters. There is no effective antidote.Calculate the percent composition by mass of the elements in mustard gas.
37 a)Calculate the average atomic mass of bromine if naturally occurring bromine is composed of 50.69% 79Br and 49.31% 81Br.(Estimate the relative atomic mass for each isotope to 3 significant figures.)b)What is the final concentration of a mixture of 1.50 liters of 1.50 M H2SO4 and 5000 mL of water?