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Quarter test Thursday 4/7Quarter test Thursday 4/7 What will be on this test?What will be on this test? Redox,net ionic, emp formula, molecular Redox,net ionic, emp formula, molecular
form, % comp, moles and molarity.form, % comp, moles and molarity. Some stuff from throughout the first 3 Some stuff from throughout the first 3
quarters. Still only have 48 minutes quarters. Still only have 48 minutes
Emp. FormulaEmp. Formula4/4/114/4/11
A compound contains 25.9% nitrogen and A compound contains 25.9% nitrogen and 74.1% oxygen. What is the empirical 74.1% oxygen. What is the empirical formula of the compound?formula of the compound?
Oh, and welcome back, hopefully refreshed and Oh, and welcome back, hopefully refreshed and excited. 75% of this school year is over!!!excited. 75% of this school year is over!!!
assume 100gram sample and convert % to gramsassume 100gram sample and convert % to grams
convert to moles convert to moles
divide by smallest molesdivide by smallest moles
make sure the ratios are whole numbersmake sure the ratios are whole numbers
Emp. FormulaEmp. Formula
4/4/114/4/11
25.9g N x 1 mole N/14 g N = 1.85 mol N25.9g N x 1 mole N/14 g N = 1.85 mol N
74.1g O x 1mol O/16g O = 4.63 mol O74.1g O x 1mol O/16g O = 4.63 mol O
NN1.851.85 O O4.63 4.63 which is weirdwhich is weird
1.85mol/1.85 =1 4.63/1.85 = 2.501.85mol/1.85 =1 4.63/1.85 = 2.50
NN11OO2.5 2.5 still can’t have fraction of atoms must bestill can’t have fraction of atoms must be
NN22 O O5 5
Molecular FormulaMolecular Formula
Calculate the molecular formula of a Calculate the molecular formula of a compound whose molar mass is 60.0 g/mol compound whose molar mass is 60.0 g/mol and empirical formula is CHand empirical formula is CH44N.N.
Molecular FormulaMolecular Formula
Either same as Emp Formula or a simple whole Either same as Emp Formula or a simple whole number multiple of the EFnumber multiple of the EF
Molar mass must be given to you, calculate efm.Molar mass must be given to you, calculate efm.
Emp. Emp. FormulaFormula
efmefm Molar Molar mass/efmmass/efm
Molecular Molecular FormulaFormula
CHCH44NN 30.030.0 60.0/30.060.0/30.0CC22HH88NN22
take this slowtake this slow
Warm-up 4/4/11Warm-up 4/4/11
What is the percent composition of Iron in What is the percent composition of Iron in Iron (II) carbonate?Iron (II) carbonate?
What is the empirical formula of a compound What is the empirical formula of a compound that is 54.1% Calcium, 43.2 % Oxygen, that is 54.1% Calcium, 43.2 % Oxygen, and 2.7% Hydrogen? and 2.7% Hydrogen?
YeeHaw!! Test Thursday! WHOOHOO!YeeHaw!! Test Thursday! WHOOHOO!
Molecular FormulaMolecular Formula
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A compound is 75.46% carbon, 4.43% A compound is 75.46% carbon, 4.43% hydrogen, and 20.10% oxygen by mass. It hydrogen, and 20.10% oxygen by mass. It has a molecular weight of 318 g/mol. has a molecular weight of 318 g/mol. What is the molecular formula?What is the molecular formula?
Molecular formulaMolecular formula
75.46g/12=6.28 75.46g/12=6.28
4.43g/1 = 4.434.43g/1 = 4.43
20.10g/16 = 1.2620.10g/16 = 1.26
Divide by smallest molesDivide by smallest moles
/ 1.26
/ 1.26
/ 1.26
= 4.98 or 5
= 3.5
= 1
So Ratio is C5H3.5O1 Which is not whole numbers
So multiply by 2
Empirical Formula is C10H7O2
Molecular formulaMolecular formula
So multiply by 2
Empirical Formula is C10H7O2
Emp. Emp. FormulaFormula
efmefm Molar Molar mass/efmmass/efm
Molecular Molecular FormulaFormula
C10H7O2 159159 318/159318/159
Multiple of 2Multiple of 2C20H14O4
HomeworkHomework
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Answer question 26-31 p 303 on notebook Answer question 26-31 p 303 on notebook paper by tomorrowpaper by tomorrow
Read Section 16.2 p480 and take notesRead Section 16.2 p480 and take notes
Answer questions 8,9 on p481Answer questions 8,9 on p481
Due tomorrow 10,11 on p 482Due tomorrow 10,11 on p 482
So quarter test, Huh!?So quarter test, Huh!?
Warm-up 4/5/11Warm-up 4/5/11
Predict product and write the net ionic Predict product and write the net ionic equation for the following.equation for the following.
MgS + CuNOMgS + CuNO3 3 ? ? Mg(NO3)2 + Cu2SNet Ionic Equation1st Find the precipitate using solubility rules
all Nitrates are solubleall Sulfides insoluble except Group 1&2 and ammonium
(S) precipitate
Net ionic ReviewNet ionic Review
MgSMgS(aq)(aq) + 2CuNO + 2CuNO3 (aq) 3 (aq) Mg(NOMg(NO33))2 2 (aq)(aq) + Cu + Cu22S S (s)(s)
Break up all aqueous solutions, DO NOT break apart the solid
Mg+2 + S-2 + 2Cu+1 + 2NO3–1 Mg+2 + 2NO3
–1 + CuCu22S S (s)(s)
Net Ionic Equation S-2 + 2Cu+1 CuCu22S S (s)(s)
Must have charges.
/ / / /
Short cut : What 2 ions make up the solid and writeShort cut : What 2 ions make up the solid and write
Daily EQ:What is molarity?Daily EQ:What is molarity?
4/6/11 warm-up4/6/11 warm-up
What is the mass of lithium dichromate What is the mass of lithium dichromate needed to make 473 ml of a 2.5M needed to make 473 ml of a 2.5M solution?solution? Must convert to liters .473 L
Substitute in equation 2.5M = X
.473L
Solve for X
What is formula and Mass?
Li2Cr2O7
X = 1.18 moles
229.8 g/mol
X 229.8 g/mol
271.2 grams
Molarity LabMolarity Lab3/22/103/22/10Let’s make a solution or 2.Let’s make a solution or 2.1) With a partner, make 20 milliliters of a 2.0 Molar 1) With a partner, make 20 milliliters of a 2.0 Molar
solution of NaCl.solution of NaCl.2)Next, make exactly 175 mL of a 0.147M solution 2)Next, make exactly 175 mL of a 0.147M solution
of NaCl.of NaCl.3) How much solution is created, if a 0.45M solution 3) How much solution is created, if a 0.45M solution
if we use 25.6 grams of sucrose (in yellow if we use 25.6 grams of sucrose (in yellow packet) to make the solution.packet) to make the solution.
Be sure to record the mass of salt used in each. Be sure to record the mass of salt used in each. Make this neat and easy for me to read/grade.Make this neat and easy for me to read/grade.
Molarity cont.Molarity cont.
4) Now actually do this. Dilute the 0.147M 4) Now actually do this. Dilute the 0.147M solution to a 0.08 M solution? How do you solution to a 0.08 M solution? How do you do this? What is new volume? How much do this? What is new volume? How much water?water?