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I’m hiring!. Homework Graders Pay = 1 extra credit point/10 papers graded Qualifications : No TUs, BD, LD Availability before/after school or 5 th period lunch. No nepotism/cronyism will be tolerated. HOMEWORK DUE MIErCOLES. If you haven’t done so already, read chapter 3!

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I m hiring
I’m hiring!

Homework Graders

  • Pay = 1 extra credit point/10 papers graded

  • Qualifications:

    • No TUs, BD, LD

    • Availability before/after school or 5th period lunch.

    • No nepotism/cronyism will be tolerated


Homework due miercoles
HOMEWORK DUE MIErCOLES

  • If you haven’t done so already, read chapter 3!

  • P114 - 115: #22, #32, #34


Stoichiometry
Stoichiometry

The quantitative study of chemical reactions


Use stoichiometry to answer these questions
Use stoichiometry to answer these questions:

How much product will form from a given amount of reactants?

How much of the reactants is necessary to form a given amount of product?



Step 1
Step 1

  • Predict products of a reaction if they are not given to you

  • Balance the coefficients of the reaction


Step 2
Step 2

  • Use molar conversion to change whatever is given (volume, mass or concentration) to moles


Step 3
Step 3

  • Use the molar ratio from the balanced reaction to convert the moles of what is given to the moles of what’s asked for.


Step 4
Step 4

  • Use conversion factors (moles  mass, volume or M) to change the moles of what is asked for to the proper unit


Calculate the volume of nh 3 formed at stp when 5 0 kg of h 2 react with excess n 2 to form nh 3
Calculate the volume of NH3 formed at STP when 5.0 kg of H2 react with excess N2 to form NH3



Calculate the mass of solid product formed when 18.4 g of MgBr2 is combined with a solution containing excess K2CO3.


Limiting reactant
Limiting Reactant MgBr

  • The reactant that gets used up

  • The reactant that determines the amount of product formed


Excess reactant
Excess Reactant MgBr

  • The reactant that Does Not get used up


When i give you quantities of more than one reactant
When I give you quantities of more than one reactant: MgBr

 You must figure out which one is limiting


3a 2b a 3 b 2 which reactant is limiting
3A + 2B MgBr A3B2Which reactant is limiting?

  • Do Step 1 and then Step 2 for both A & B.

  • Pick A (your chemistry grade?)

  • Use the molar ratio that relates A to B to determine how much of B would be needed to completely use up the moles of A

  • If there are more than enough moles of B, A is limiting

  • If there not enough moles of B, then B is limiting

  • Use limiting reactant for steps 3 & 4


Calculate the mass of glucose (C MgBr6H12O6) formed when 880 g of carbon dioxide is combined with 720 g of water in photosynthesis


Calculate the mass of baso 4 formed when 104 g of bacl 2 is combined with 250 ml 1 00 m k 2 so 4
Calculate the mass of BaSO MgBr4 formed when 104 g of BaCl2 is combined with 250 mL 1.00 M K2SO4


How to make a blt sandwich
How to make a BLT sandwich: MgBr

2 LL

(lettuce

leaves)

5 BS

(bacon

slices)

3 TS

(tomato

slices)

2 PB

(pieces

bread)

+

+

+


So reaction is
So reaction is: MgBr

  • 2 PB + 3 TS + 5 BS + 2 LL  1 BLT

    1 BLT


Masses of reactants product
Masses of reactants + product: MgBr

  • 1 PB = 50.0 g

  • 1 TS = 60.0 g

  • 1 BS = 20.0 g

  • 1 LL = 5.0 g

  • 1 BLT = 390.0 g


How many blts
How many BLTs? MgBr

  • PB = 3,356.7 g

  • TS = 4,789.2 g

  • BS = 2,789.4 g

  • LL = 789.2 g

    Get answer in significant digits and then round down to whole number of BLTs.


Theoretical yield
Theoretical Yield MgBr

  • The amount determined through stoichiometry

  • The amount solved for on paper


Experimental yield
Experimental Yield MgBr

  • The amount obtained in the lab

  • Actual yield


Percent yield
Percent yield MgBr

  • % Yield = (Exp/Theo) x 100 %


68 g nh 3 was obtained when 140 g of n 2 reacts with excess h 2 calculate percent yield
68 g NH MgBr3 was obtained when 140 g of N2 reacts with excess H2. Calculate percent yield.


510 g PH MgBr3 was obtained when 0.62 kg of P4 reacts with excess H2. Calculate percent yield.


4.61 g of lead(II)iodide was obtained when 66.2 g of lead(II)nitrate was added to 750 ml 0.10 M potassium iodide. Calculate the % yield.



Determine the volume of NH 12 kg of erythrose (C3 formed at STP when 2.0 x 1027 molecules N2 reacts with 4.0 kg of H2:


Determine the volume of O 12 kg of erythrose (C2 released at STP when 32 kg of Fe2O3 is purified making

Fe & O2


Calculate the mass of solid product formed when 41.6 g of barium chloride is added to 250 ml of 0.40 M potassium sulfate giving a 50.0 % yield:


Calculate the mass of solid product formed when 2.00 g of calcium bromide is added to 250 ml of 0.40 M sodium sulfate:


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