Quantitative RelationshipsQuantitative Relationships

(Stoichiometry)(Stoichiometry)

Lets take a moment… sit back… Lets take a moment… sit back… relax… and review some relax… and review some previously learned concepts…previously learned concepts…

Review of Classifying and Review of Classifying and Balancing Chemical Balancing Chemical

EquationsEquations

6 main types of chemical reactions:6 main types of chemical reactions:

Formation (simple composition):Formation (simple composition): elements elements compoundcompound

Simple decomposition:Simple decomposition: compound compound elements elements

Single replacement:Single replacement: element + compound element + compound element + compoundelement + compound

Double Replacement:Double Replacement: compound + compound compound + compound compound + compoundcompound + compound

Complete combustion:Complete combustion: substance + oxygen substance + oxygen most common oxidesmost common oxides

Other:Other: any reaction that does not fit in the above any reaction that does not fit in the above categoriescategories

The coefficients that are placed in front of the The coefficients that are placed in front of the compounds and elements represent the compounds and elements represent the mole-to-mole-to-molemole ratio of the reactants and products. ratio of the reactants and products.

Ex. 2NaClEx. 2NaCl(aq)(aq) + MgSO + MgSO4(aq)4(aq) → Na→ Na22SOSO4(aq)4(aq) + MgCl + MgCl2(s)2(s)

2 moles2 moles of sodium chloride reacts with of sodium chloride reacts with one moleone mole of of magnesium sulfate to produce magnesium sulfate to produce one moleone mole of sodium sulfate of sodium sulfate and and one moleone mole of magnesium chloride of magnesium chloride

When you are making quantitative calculations, When you are making quantitative calculations, please use the please use the mole-to-molemole-to-mole ratio in your ratio in your calculationscalculations

::

Mole-to-Mole StoichiometryMole-to-Mole Stoichiometry

Calculations that make use of a balanced Calculations that make use of a balanced equation and information about one equation and information about one substance to calculate information about a substance to calculate information about a differentdifferent substance are called substance are called stoichiometric calculationsstoichiometric calculations

The simplest stoichiometric calculations The simplest stoichiometric calculations are those where the quantities are are those where the quantities are measured in moles.measured in moles.

Follow these steps for mole-to-mole Follow these steps for mole-to-mole questions:questions:

1)1) Write balanced equation for the reaction. Write balanced equation for the reaction. Determine the two substances involved Determine the two substances involved as being the as being the givengiven or the or the unknownunknown..

2)2) Determine the number of moles of one Determine the number of moles of one substance.substance.

3)3) Set up a mole ratio using coefficients of Set up a mole ratio using coefficients of the balanced equation for the two the balanced equation for the two substances. Substitute values in mole substances. Substitute values in mole ratio for the given and unknown.ratio for the given and unknown.

4)4) Solve the equation.Solve the equation.

ExampleExample

How many moles of oxygen gas are needed to How many moles of oxygen gas are needed to react completely with 3.50 mol of hydrogen gas react completely with 3.50 mol of hydrogen gas to produce water vapor?to produce water vapor?

1)1) Write balanced equation for the reaction.Write balanced equation for the reaction.

2H2H2(g)2(g) + O + O2(g)2(g) → 2H→ 2H22OO(g)(g)

2) Determine the two substances involved as 2) Determine the two substances involved as being thebeing the knownknown or the or the unknownunknown..

Known:Known: 3.50 mol of hydrogen 3.50 mol of hydrogenUnknown:Unknown: ? mol of oxygen ? mol of oxygen

2H2H2(g)2(g) + O + O2(g)2(g) → 2H→ 2H2200(g)(g)

3) 3) MultiplyMultiply the known amount of moles by the the known amount of moles by the unknown molar coefficientunknown molar coefficient and and dividedivide by the by the known molar coefficientknown molar coefficient..

n xn x nn unknown unknown nn known known

3.50 mol H3.50 mol H22 x x 1 mol O1 mol O22

2 mol H 2 mol H22

4) Solve the equation.4) Solve the equation.

nnO2O2 = 1.75 mol = 1.75 mol

Try this one…Try this one…Example 1:Example 1:

Nitrogen monoxide gas may be prepared by reacting copper metal Nitrogen monoxide gas may be prepared by reacting copper metal with dilute nitric acid. with dilute nitric acid.

3Cu3Cu(s)(s) + 8HNO + 8HNO3(aq)3(aq) → 3Cu(NO→ 3Cu(NO33))2(aq)2(aq) + 2NO + 2NO(g)(g) + 4H + 4H2200(l)(l)

Determine the number of moles of nitrogen monoxide that can be Determine the number of moles of nitrogen monoxide that can be obtained from the reaction of 0.75 moles of copper with an excess obtained from the reaction of 0.75 moles of copper with an excess of nitric acid.of nitric acid.

Mole-to-Mass StoichiometryMole-to-Mass Stoichiometry When we carry out a chemical reaction, we usually When we carry out a chemical reaction, we usually

measure solids by their masses. measure solids by their masses. To perform mole to mass stoichiometric calculations, To perform mole to mass stoichiometric calculations,

follow these steps:follow these steps:

1)1) Write a balanced equation for the reaction. Write a balanced equation for the reaction.

2)2) Determine the number of moles of one substance.Determine the number of moles of one substance.

3)3) From the balanced equation, set up a mole ratio From the balanced equation, set up a mole ratio using coefficients of the balanced equation for the using coefficients of the balanced equation for the two substances. Substitute values in mole ratio for two substances. Substitute values in mole ratio for the given and the unknown. Solve the equation for the given and the unknown. Solve the equation for the unknown number of moles.the unknown number of moles.

4)4) Convert unknown moles into mass. Convert unknown moles into mass. (m=nxM)(m=nxM)

Example 2:Example 2:Copper metal reacts with a solution of silver nitrate to produce Copper metal reacts with a solution of silver nitrate to produce silver and copper (II) nitrate. What mass of silver can be silver and copper (II) nitrate. What mass of silver can be produced by reacting 0.250 mol of copper?produced by reacting 0.250 mol of copper?

Example 3:Example 3:Sulfuric acid is neutralized by sodium hydroxide solution. Sulfuric acid is neutralized by sodium hydroxide solution. What mass of sodium sulfate can be produced by reacting What mass of sodium sulfate can be produced by reacting 0.350 mol of NaOH0.350 mol of NaOH(aq)(aq)??

Mass-to-Mole StoichiometryMass-to-Mole Stoichiometry In a mass-to-mole problem, you will be given the In a mass-to-mole problem, you will be given the

mass of a substance and you will determine the mass of a substance and you will determine the number of another substance.number of another substance.

For these types of questions, please follow these For these types of questions, please follow these steps:steps:

1)1) Write a balanced equation for the reaction.Write a balanced equation for the reaction. 2)2) Calculate the number of moles for the given Calculate the number of moles for the given

substance. substance. (n = m/M)(n = m/M)

3)3) Set up a mole ratio using coefficients of the balanced Set up a mole ratio using coefficients of the balanced equation for the two substances.equation for the two substances. Substitute values Substitute values in the mole ratio for the in the mole ratio for the knownknown and the and the unknownunknown..

4)4) Solve the equation for the unknown number of Solve the equation for the unknown number of moles.moles.

Example 4:Example 4:How many moles of water vapor can be produced by reacting How many moles of water vapor can be produced by reacting 101g of oxygen gas with sufficient hydrogen gas?101g of oxygen gas with sufficient hydrogen gas?

V. Mass-to-Mass V. Mass-to-Mass StoichiometryStoichiometry

In this type of question, you are provided with the In this type of question, you are provided with the mass of one substance and asked to calculate the mass of one substance and asked to calculate the mass of another substance in the equation.mass of another substance in the equation.

To solve these types of problems, follow these steps.To solve these types of problems, follow these steps.

1)1) Write a balanced equation for the reaction.Write a balanced equation for the reaction.

2)2) Calculate the number of moles for the given Calculate the number of moles for the given substance. substance. (n = m / M)(n = m / M)

3)3) Set up a mole ratio for the known and unknown. Set up a mole ratio for the known and unknown. Solve the equation for the unknown number of moles.Solve the equation for the unknown number of moles.

4)4) Convert unknown number of moles to mass. Convert unknown number of moles to mass. (m = n x M)(m = n x M)

Example 5:Example 5:What mass of aluminum oxide must be decomposed to What mass of aluminum oxide must be decomposed to produce 80.0 g of oxygen gas?produce 80.0 g of oxygen gas?

Hint of Gravimetric (Mass) Hint of Gravimetric (Mass) StoichiometryStoichiometry

**When dealing with mass **When dealing with mass stoichiometry, be sure to convert stoichiometry, be sure to convert all masses to moles before all masses to moles before performing the mole ratio.performing the mole ratio.

Volume to Volume Volume to Volume StoichiometryStoichiometry

In this type of question, you are working with solutions.In this type of question, you are working with solutions. To perform solution problems, follow these steps:To perform solution problems, follow these steps:

1)1) Write a balanced chemical equation. Determine the Write a balanced chemical equation. Determine the two substances involved as being the given quantity two substances involved as being the given quantity and the unknown quantity.and the unknown quantity.

2)2) Calculate the number of moles of the given substance Calculate the number of moles of the given substance using n = c x vusing n = c x v

3)3) From the balanced equation, set up a mole ratio using From the balanced equation, set up a mole ratio using coefficients of the balanced equation for the two coefficients of the balanced equation for the two substances. Substitute values in mole ratio for the substances. Substitute values in mole ratio for the given and the unknown. Solve the equation for the given and the unknown. Solve the equation for the unknown number of moles.unknown number of moles.

4)4) Convert the number of moles to a volume.Convert the number of moles to a volume.

Example 6:Example 6:What volume of a 0.250 mol/L hydrochloric acid is needed to What volume of a 0.250 mol/L hydrochloric acid is needed to completely react with 250 mL of a 0.156 mol/L magnesium completely react with 250 mL of a 0.156 mol/L magnesium hydroxide solution?hydroxide solution?

Combined QuestionsCombined Questions

You will encounter questions where You will encounter questions where you will have to convert from mass you will have to convert from mass to volume or volume to mass, etc.to volume or volume to mass, etc.

Use the steps previously provided for Use the steps previously provided for you, but adjust the steps to the you, but adjust the steps to the specific situation in the question.specific situation in the question.

Review of StoichiometryReview of Stoichiometry

Calculations that make use of a balanced Calculations that make use of a balanced chemical equation are known as stoichiometric chemical equation are known as stoichiometric calculations. calculations.

The common feature to all stoichiometric The common feature to all stoichiometric calculations is the use of the mole calculations is the use of the mole relationships indicated in a balanced equation.relationships indicated in a balanced equation.

Summary of steps for Summary of steps for anyany stoichiometry question: stoichiometry question:

1)1) Always write a correctly balanced chemical Always write a correctly balanced chemical equation. equation.

2)2) Change the given / Change the given / knownknown quantity to mole using quantity to mole using one of the following equations.one of the following equations. { { n = m/M or n = C∙Vn = m/M or n = C∙V}}

3)3) Find the required or Find the required or unknownunknown number of moles number of moles using the mole to mole ratio.using the mole to mole ratio.

4)4) Convert the required number of moles to volume, Convert the required number of moles to volume, mass, or concentration using the appropriate mass, or concentration using the appropriate formula. formula. {{v = n/c or m = nM or c = n/vv = n/c or m = nM or c = n/v}}

Question 1:Question 1:Aluminum metal can be refined from the ore of aluminum called bauxite. In the Aluminum metal can be refined from the ore of aluminum called bauxite. In the refining process aluminum oxide decomposes to aluminum and oxygen gas. What refining process aluminum oxide decomposes to aluminum and oxygen gas. What mass of aluminum can be produced from 2.04 kg of aluminum oxide?mass of aluminum can be produced from 2.04 kg of aluminum oxide?

2 Al2 Al22OO3(s)3(s) → 4 Al→ 4 Al(s)(s) + 3 O + 3 O2(g)2(g)

Question 2:Question 2:

Iron (III) phosphate reacts with tin (IV) nitride to produce iron (III) nitride and tin (IV) Iron (III) phosphate reacts with tin (IV) nitride to produce iron (III) nitride and tin (IV) phosphate.phosphate.

4 FePO4 FePO4(aq04(aq0 + Sn + Sn33NN4(aq)4(aq) → 4 FeN→ 4 FeN(aq)(aq) + Sn + Sn33(PO(PO44))4(aq)4(aq)

a)a) How many moles of tin (IV) nitride are needed to produce 0.0500 mol of iron (III) nitride?How many moles of tin (IV) nitride are needed to produce 0.0500 mol of iron (III) nitride?

b)b) How many moles of iron (III) phosphate are used when 0.045 mol of tin (IV) nitride also How many moles of iron (III) phosphate are used when 0.045 mol of tin (IV) nitride also reacts?reacts?

Question 3:Question 3:Ammonia reacts with hydrochloric acid to produce ammonia chloride. What Ammonia reacts with hydrochloric acid to produce ammonia chloride. What mass of ammonia is needed to produce 36.1g of ammonium chloride?mass of ammonia is needed to produce 36.1g of ammonium chloride?

NHNH3(g)3(g) + HCl + HCl(aq)(aq) → NH→ NH44ClCl(s)(s)

Question 4:Question 4:150 mL of a 0.367 mol/L solution of sodium nitrate reacts with 225 mL of 150 mL of a 0.367 mol/L solution of sodium nitrate reacts with 225 mL of potassium carbonate. What is the concentration of the potassium carbonate potassium carbonate. What is the concentration of the potassium carbonate solution?solution?

2 NaNO2 NaNO3(aq)3(aq) + K + K22COCO3aq)3aq) → Na → Na22COCO3(asq)3(asq) + 2 KNO + 2 KNO3aq3aq

Question 5:Question 5:Sodium chloride solution reacts with 100 mL of a 1.50 mol/L solution Sodium chloride solution reacts with 100 mL of a 1.50 mol/L solution of silver nitrate. Using the following equation, calculate the mass of of silver nitrate. Using the following equation, calculate the mass of precipitate produced.precipitate produced.

NaNa22SS(aq)(aq) + 2 AgNO + 2 AgNO3(aq)3(aq) → 2 NaNO→ 2 NaNO3(aq)3(aq) + Ag + Ag22SSs)s)