topic: stoichiometry daily question: what is the importance of the coefficients in a chemical...

Topic: Stoichiometry

Daily Question: What is the importance of the coefficients in a chemical equation?

Do now: Complete the do-now on the worksheet.

Sandwiches

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Sandwiches

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Stoichiometry

Problem

Methane combustion

Topic: The Mole Concept

Daily Question: What is a mole?

Do now: Complete the do-now on the worksheet.

Avogadro’s #

1 mole of any substance is defined as 6 x 1023 of that substance. So if I had 1 mol of Mr. Bennetts, I’d have 6 x 1023 Mr. Bennetts. (that would be awesome ).

Think of a mole as a CRAZY BIG dozen. It’s the same concept.

The mass of one mole of any atom is its atomic weight in grams. That is the origin of the number.

Molar Mass

To calculate molar mass of a substance, take the # of each type of atom and multiply it by the atomic mass (found on the periodic table).

Ex: ethanol (C2H6O).

C : 2 x 12 g/mol = 24 g/molH : 6 x 1 g/mol = 6 g/molO : 1 x 16 g/mol = 16 g/molTotal: 46 g/mol

Factor Label Method

To convert between moles and grams we use the factor label method. We use the molar mass as a conversion factor (think of a ratio).

Ex: How many grams are in 2.5 moles of ethanol

Topic: Stoichiometry - 2

Daily Question: How can we predict the amount of matter than can be made?

Do now: If I start with 44 g of oxygen gas in a combustion reaction, how many moles are there?

Worksheet problems

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#18 6.25 mol of CH4 and 6.25 mol of O2

Worksheet problems

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#21 O2 runs out first

Worksheet problems

#22 Since O2 runs out first, you can make 3.13 mol of CO2.

#23 44 g/mol

#24

Worksheet problems

#25 18 g/mol

#26 Start with moles of O2 because we know it

runs out first.

Worksheet problems

#27

Practice problems

If 32 g of propane, C3H8, are combusted, how much oxygen is consumed? Start by writing the balanced chemical equation.

Practice problems

C3H8 + 5O2 3CO2 + 4H2O

Practice problems

A solution containing 25 g of aluminum nitrate is mixed with a solution of 40 g of sodium hydroxide. How much solid can be made.

Start with the chemical formulas, make a balanced chemical equation, then determine the solid.

Practice problems

Aluminum nitrate = Al(NO3)3

Sodium hydroxide = NaOH

Al(NO3)3(aq) + 3NaOH(aq) Al(OH)3(?) + 3NaNO3(?)

Practice problems

Al(NO3)3(aq) + 3NaOH(aq) Al(OH)3(S) + 3NaNO3(aq)

Aluminum nitrate runs out first, so 9.15 g can be made

Topic: The Breathing Diet

Daily Question: How much weight do we lose in a year from breathing?

Do now: If an iphone is made from 1 screen, 3 circuit boards and 2 cameras, how many iphones can be made from 200 screens, 500 circuit boards, and 500 cameras. What piece limits the amount that can be made?

Limiting Reactant

• In most chemical reactions, one of the reactants will run out before the others. This is called the limiting reactant. To find the limiting reactant, determine how much product can be made from each reactant. The one that produces the least product runs out first and is the limiting reactant.

Percent Yield

• In real-world chemical reactions, we don’t obtain 100% of what we would expect. This is due to losses of product on the walls of container, incomplete reactions, and other reasons. To determine the percent yield, use the equation below:

Practice ProblemIf 10 g of methane, CH4, is burned in 30 g of O2, how much CO2 is produced? If only 17 g was collected what is the percent yield?

Practice ProblemCH4 + 2O2 CO2 + 2H2O

O2 is the limiting reactant

Practice Problem

82.5% yield