Bellwork Wednesday Dig around in your brain and fill in the following… 1 mole = ___________________ atoms 1 mole = ___________________ liters 1 mole = ___________________ g H2O 3 mole = ________________ molecules

CHEMISTRY Unit 8 CHAPTER 12 Stoichiometry

Just What is a Chemical Ratio? A mole ratio is like making a s’more. The “chemical reaction for a s’more would be… 3 chocolate squares + 1 marshmallow + 2 graham crackers  1 s’more If you want to make 3 s’mores, how many marshmallows would you need? 3 s’mores = 3 marshmallows If you have 27 chocolate squares, how many smores can you make? 3 chocolate squares = 1 s’more so 27 chocolate squares = 9 s’mores

12.1 Stoichiometry – study of calculations of quantities in chemical reactions using balanced chemical equations. 2Mg + O2  2MgO 2 moles Mg + 1mole O2  2 moles MgO

2Mg + O2  2MgO The mole ratios can be obtained from the coefficients in the balanced chemical equation. What are the mole ratios in this problem? Mole ratios can be used as conversion factors to predict the amount of any reactant or product involved in a reaction if the amount of another reactant and/or product is known.

Mole Ratio! What’s that mean? Well, a stoichiometry problem gives you an amount of one chemical and asks you to solve for a different chemical. To get from one type of chemical to another, a MOLE RATIO must be found between the two chemicals. You get the MOLE RATIO from the BALANCED CHEMICAL EQUATION!

The mole map Always follow the road map… Do not make up new paths! R.P. of substance given R.P. of substance wanted Coefficients in a balanced equation! Atoms, formula units, molecules 6.02 x 1023 1mol Atoms, formula units, molecules 6.02 x 1023 1mol Mass of substance given Moles of substance given Moles of substance wanted Mass of substance wanted gfm 1mol gfm 1mol grams mol mol grams 22.4 L 1mol 22.4 L 1mol Always follow the road map… Do not make up new paths! Volume of substance given Volume of substance wanted L, mL L, mL

*the coefficients are* A balanced chemical equation tells the quantity of reactants and products as well as what they are. 2 mol 1 mol 2 mol *the coefficients are* Mole Ratios

The MOLE RATIO is the bridge between the two different chemicals The MOLE RATIO is your mechanism of transition between the chemical that is your starting given and the chemical you are solving for. The MOLE RATIO is the bridge between the two different chemicals moles moles (given) (want) Mole Ratio ? want given

12.2 Mole - Mole Calculations – Mole ratios are used to calculate the number of moles of product from the given number of moles of reactant, or vice versa. Lets get back to those s’mores. If you have the following reaction… 3 chocolate squares + 1 marshmallow + 2 graham crackers  1 s’more You have 325 chocolate squares and you want to make the maximum number of s’mores possible. Show a calculation for this reaction. 325 c.s. 1 s’more = 108.3333 or 108 s’mores 3 c.s.

EXAMPLE Calculate the number of moles of Na2O that will be produced when 5.00 moles of Na completely react with oxygen gas. 4Na + O2  2Na2O 5.00 mol Na 2 mol Na2O = 2.50 mol Na2O 4 mol Na mol-mol ratio

Mole-Mass Calculations: We use mole ratios from balanced chemical equations and the molar conversions from Ch. 7 to calculate amounts (grams) of substances needed or produced in chemical reactions.

EXAMPLE mol-mol ratio GFM How many grams of KClO3 must decompose to produce KCl and 1.45 moles O2? 2KClO3 → 2KCl + 3O2 1.45 moles O2 2 mol KClO3 122.6 g KClO3 = 3 mol O2 1 mol KClO3 119 g KClO3 mol-mol ratio GFM

Mass-Mass Calculations: Same as mole-mass calculations, with an additional step of converting mass to moles.

EXAMPLE GFM mol-mol ratio GFM When 24.0 g of Na are mixed with Cl2, are 52.0 g of NaCl produced? Explain. 2 Na + Cl2 → NaCl 2 1 mol Na 2 mol NaCl 58.5 g NaCl 24.0 g Na = 23.0 g Na 2 mol Na 1 mol NaCl GFM mol-mol ratio GFM 61.0 g NaCl Are 52.0 g produced? Actually more than 52.0 g were produced.

CaCO3, limestone, is heated to produce calcium oxide, CaO, and CO2 CaCO3, limestone, is heated to produce calcium oxide, CaO, and CO2. What mass of limestone is required to produce 156.0 g of CaO? CaCO3 (s)  CaO (s) + CO2 (g) 156.0 g CaO 1 mol CaO 1 mol CaCO3 100.1 g CaCO3 56.1 g CaO 1 mol CaO 1 mol CaCO3 GFM mol-mol ratio GFM 278.4 g CaCo3 =

I will take up the lab in a moment Summary part 1 p.139

Bellwork Thursday Magnesium metal reacts with oxygen in a synthesis reaction. Write and balance the equation, then fill in the chart concerning the particles and mass. Total Particles of Reactants  Total Particles of Products Total Moles of Reactants Total Moles of Products Total Mass of Reactants Total mass of Products