Basic Concepts on Stoichiometry Mr. Ronnie Z. Valenciano Jr.Bachelor of Secondary Education Major in Biological Science
What is a MOLE?• It is the SI unit of the quantity of matter.• It represents a specific quantity of atoms, ions or molecules. 23 1 mole = 6.02 x 10 Avogadro’s number
Mole – Mass RelationshipSteps:1. Get the molecular mass of the given substance.2. Then use the conversion factor remembering that one mole of any substance has a mass, in grams, equal to its molecular (atomic) mass.3. Accomplish the mathematical equation.
Exercises on mole – mass relationship.• What is the mass of 2 mol of NH3?• A container holds 45 g of sugar (C6H12O6). How many moles of sugar are present?• How many moles are present in 27.0 g of water?
Balancing Equations Steps:1. Determine the reactants and products.2. Assemble the parts of the chemical reaction.3. Balance the equation
Balance the following equation:1. N2 + H2 NH32. NH3 + O2 N2 + H203. Al + S Al2S34. C6H12O6 CO2 + H2O
Mass – Mass RelationshipSteps:1. Write the balanced equations.2. Find the number of moles of the given substance.3. Inspect the balance equation to determine the ratio moles of required substance to moles of given substance.4. Express the moles of required substance in terms of gram, then convert moles to grams.
Stoichiometry overview•Recall that in stoichiometry the mole ratio provides a necessary conversion factor: molar mass of x molar mass of ygrams (x) moles (x) moles (y) grams (y) mole ratio from balanced equation• We can do something similar with solutions: mol/L of x mol/L of yvolume (x) moles (x) moles (y) volume (y) mole ratio from balanced equation
Problem SolvingConsider the reaction of ammonia with oxygen to produced nitrogen monoxide and water. 4NH3 + 5O2 4NO + 6H2O If 2.85 g of ammonia reacts completely with excess oxygen what mass of water can be obtained?
• The principal constituent of natural gas is methane, which burns in air according to the reaction. CH4 + 2O2 CO2 + 2H2O How many grams of oxygen gas are needed to produce 3.50 g of carbon dioxide?
• Tungsten (W) metal, which is used to make incandescent bulb filaments is produced by the reaction, WO3 + 3H2 3H2O + W How many grams of hydrogen gas are needed to produced 1.00g of tungsten?
Calcium hydroxide is sometimes used in water treatment plants to clarify water for residential use. Calculate the volume of 0.0250 mol/L calcium hydroxide solution that can be completely reacted with 25.0 mL of 0.125 mol/L aluminum sulfate solution. Al2(SO4)3(aq) + 3Ca(OH)2(aq) 2Al(OH)3(s) + 3CaSO4(s) # L Ca(OH)2= 0.0250 0.125 mol Al2(SO4)3 3 mol Ca(OH)2 L Ca(OH)2 x x xL Al2(SO4)3 L Al2(SO4)3 1 mol Al2(SO4)3 0.0250 mol Ca(OH)2 = 0.375 L Ca(OH)2
• H2SO4 reacts with NaOH, producing water and sodium sulfate. What volume of 2.0 M H2SO4 will be required to react completely with 75 mL of 0.50 mol/L NaOH?H2SO4(aq) + 2NaOH(aq) 2H2O + Na2SO4(aq)# L H2SO4= 0.50 mol NaOH 1 mol H2SO40.075 L NaOH x x L NaOH 2 mol NaOH L H2SO4 x = 0.009375 L = 9.4 mL 2.0 mol H2SO4
How many moles of Fe(OH)3 are produced when 85.0 L of iron(III) sulfate at a concentration of 0.600 mol/L reacts with excess NaOH? Fe2(SO4)3(aq) + 6NaOH(aq) 2Fe(OH)3(s) + 3Na2SO4(aq)# mol Fe(OH)3=85 L Fe2(SO4)3 x 0.600 mol Fe2(SO4)3 x 2 mol Fe(OH)3 L Fe2(SO4)3 1 mol Fe2(SO4)3 = 102 mol