Chemistry Study Guide 1 - Chapter 16

Reads: 1575  | Likes: 0  | Shelves: 0  | Comments: 0

More Details
Status: Finished  |  Genre: Other  |  House: Booksie Classic
Regular Chemistry, chapter 16

Submitted: September 21, 2009

A A A | A A A

Submitted: September 21, 2009

A A A

A A A


Chapter 16 Test Review for Chemistry
Example Questions
1. 27.4 mL of 0.0154 M Ba(OH)2 is added to a 20.0 mL sample of HCl soln. What is molarity of HCl?
 
Step one:
Write balanced equation
Ba(OH)2 + 2HCl –> 2H2O + BaCl2
^Known^Unknown
 
Step two:
Find mol of known
M= moles Ba(OH)2/volume of soln. = # = MxVol.
# of Ba(OH)2 = (0.0154M/ L of soln)(0.0274)
=4.22e-4 mol Ba(OH)2
Step Three:
Use mole ratio to convert moles from known to unknown
(4.22e-4)(2 mol)= 8.44e-4
Step Four:
Calc. Molarity of unknown
M= moles HCl/L of soln. = 8.44e-4/0.020 L = 4.22e-2 M HCl
 
2. In a laboratory experiment involving the neutralization of HCl using 0.500 M KOH, the following data were collected:
 
Trial One: 10.00 mL 19.8mL
Trial Two:15.00mL 30.05mL
Trial Three20.00mL 40.00mL
 
Write a balanced equation:
HCl + KOH –> H2O + KCl
 
Write Net Ionic:
H + OH –> H2O
 
What is the molarity of the acid in each trail? What is the average acid molarity?
 
VaMa = VbMb
Trial ONE
Ma-> (.0198 L) (0.5M KOH)/ 0.01 L = 0.99 M HCl
Trial TWO
Ma-> (.03005) (0.5)/ 0.015 L = 1.001 M HCL
Trial THREE
Ma-> (.040) (0.5)/.02 L = 1 M HCl
Add All/3 = Average (0.997 M HCl)
 
3. What is the pH of 0.00125 M HBr? If 175mL of this soln is diluted to a total volume of 3L, what is the pH of the diluted soln?
 
pH = -log([H3O+])
pH = -log(0.00125) <- type in to calc.
(Make sure it’s a one to one ratio)
HBr -> H3O + Br
1st answer: pH = 2.9
For Diluted soln.:
Step one:
Find V1M1=V2M2
(0.175 L)(0.00125M) = (3)(?)
= 7.29e-5 M
Step Two:
pH = -log(7.29e-5)
2nd answer = 4.14pH
 
4. What is [OH-] in 5.4e-5 M MgOH?
Write balanced equation:
Mg(OH)2 -> Mg+2 + 2OH-
Mg(OH)2 = 2 times concentration [OH-]
Double it.
(5.4e-5)(2)
=1.08e-4
 
5. Determine the pH of 0.00118 M HBr acid.
Balanced equation
HBr -> H3O + Br-
pH = -log(H3O)
-log(0.00118)
= 2.92 pH
 
6. What is the molarity of a CaOH soln w/ pH of 10.8?
Balanced equation
Ca(OH)2 -> 2OH + Ca2+
14= pH + pOH
14-10.8= 3.2
3.2= pH
Find molarity
3.2 = -log[OH-]
Take anti-log
-3.2 = OH
10^-3.2 in calc.
OH = 6.3e-4
Use mole ratio
6.3e-4/2 = 3.15e-4 M CaOH
7. Calc the pH of soln w/ [OH] of 6.9e-10 M
Calc pOH -> -log(6.9e-10) = 9.16 pOH
pOH + pH = 14
14-9.16 = 4.84 pH
 
8. What is [OH-] in chocolate milk if [H3O+] = 4.5e-7 M? Is it acidic, basic, or neutral?
OH- = 2.18e-8
It’s acidic
 
Notes
[H3O+][OH-] = 1e-14 together, 1e-7 apart.
Kw = [H3O][OH] = 1.0e-14 M
Temp Variances:
0 degrees C 1.2e-15
10 degrees C3.0e-15
25 degrees C1.0e-14
50 degrees C5.3e-14
 
Calculating [H3O] and [OH] {given:1.0e-2}
Write out equation
NaOH -> Na + OH
1.0e-2 mol NaOH x one mol OH/ one mol NaOH = 1.0e-2 OH/ L soln.
= 1.0e-2 M OH
If pH = 2, [H3O] = 10^-2
If pH = 2.2, [H3O] = 10^-2.2 (enter in calc.) = 1.0063
pH = -log(H3O)
pOH = -log(OH)
pH + pOH = 14
 
Vocabulary
Self ionization of water: Two water molecules produce a hydronium ion and a OH- by transfer of a proton.
Acid-Base Indicators: compounds whose colors are sensitive to pH.
Transition Interval: the pH range over which an indicator changes color.
pH Meter: determines the pH of a soln by measuring the voltage between the two electrodes that are placed in a soln.
Titration: controlled addition and measurement of the amt of a soln of known concentration required to react completely with a measured amt of a soln of unknown concentration.
Equivalence Point: the point at which the two solns used in a titration are present in chemically equal amts.
End Point: point of titration at which an indicator changes its color.
Standard soln: soln that contains the precisely known concentration of a solute
Primary Standard: highly purified solid compound used to check the concentration of the known soln in a titration.


© Copyright 2019 TheStudentHelper. All rights reserved.

Add Your Comments: