If HA and NaOH were titrated to determine the molar mass of the unknown monoprotic acid and the NaOH was not completely dry, would the calculated molar mass be lower, higher, or equal to than the exact.
What is too high? (excess water adds to the final molar mass)
100
This gas results in a reinitiation of a flame on a splint.
What is oxygen?
100
This apparatus is used in the process commonly as titration.
What is a buret?
100
List an error that would cause the calculated molar mass to be too low in a gravimetric analysis
What is the end sample being weighed when still damp/wet?
100
The device used to calculate the heat of a reaction.
What is a calorimeter?
200
Type of solution needed in the Erlenmeyer flask in a titration.
What is an indicator, acid, or base?
200
Which is a precipitate reaction?
1.) SO3 + H2O --> H2SO4
2.) 2AgNO3 + Na2S --> Ag2S + 2NaNO3
3.) CH4 + 2O2 --> CO2 + 2H2O
What is number 2?
(2AgNO3 + Na2S --> Ag2S + 2NaNO3)
200
List at least three materials necessary to perform the dehydration of a solution.
What is an Erlenmeyer flask, filter paper, filter, vacuum tubing, ring stand, spatula, and clamp.
200
A 10g sample of a hydrate BaCl2 was heated, and only 7.2g of anhydrous salt remained. What was the percentage of water?
What is 28%?
10g - 7.2g = 2.8g/10 = .28 x 100 = 28%
200
q of water = -17,600J
~the initial temp. = 43.6 degrees C
~the C of water = 4.184J/degrees C
~mass of water = 1600g
FIND THE FINAL TEMPERATURE
What is 40.97 degrees C
300
Which indicator would be most useful in identifying the equivalence point of a titration for a solution that has an [H+] of .0040 at the equilvalence point?
What is Methyl violet (pH range for color change is 0.1-2.0)?
300
Which reactant is in excess and how many moles are there when 2 parts H2 gas react with 4 parts O2 gas?
What is 3 moles of O2 gas?
300
The process of strong heating and rapid cooling followed by gentle reheating and slow cooling.
What is tempering?
300
FIND THE PERCENT BARIUM IN BaSO4 SAMPLE
~3.09x10-3 mol Ba
~137.33 g/mol Ba
~1.45g sample BaSO4
What is 29.3% Barium
3.09x10-3 x 137.33 = 0.424 g
0.424 g / 1.45 g =0.293 x 100 = 29.3%
300
In a Southwest Steak Breakfast Burrito from Dunkin Donuts, there are 18 calories/ 1 gram. The value of food burned was 7 grams. What is the q of food?
What is 2.57 cals/gram
400
A 30mL solution of 0.5M NaOH is titrated with a 60mL sample of HCl. Determine the unknown concentration of HCl.
What is
[OH-]=0.5M
0.5M x .030L NaOH = 0.015 mol NaOH= 0.015 mol HCl (1:1)
0.015 mol / .060L = 0.25M HCl
400
How is NO gas most commonly produced? Which reactant is oxidized during this process?
(Show reaction.)
What is being reacted with ammonia? Ammonia is oxidized.
4 NH3 + 5 O2 → 4 NO + 6 H2O
(brown gas)
400
Why and how are volumetric flasks used? What is their purpose?
What is to measure specific volume at a certain temperature. They are used in the preparation of standardized solutions.
400
What percentage of water is found in Na2S x 9H2O?
What is 67.5%?
(9H2O/Na2S x 9H2Og) =
(162.18g H2O/240.23g Total) x100 = 67.5%
400
FIND THE MASS OF WATER
~total mass of sample = 90.0 grams
~temperature increases from 35.5 degrees C to 47 degrees C
~1.0-gram sample burned
~q of food = -690
What is 60.0 grams water?
500
What volume of a 3.0M solution of hydrochloric acid is required to neutralize 125 mL of 1.0M NaOH solution?
What is 375 mL?
(.125L x 3.0 moles/L = .375 moles NaOH; .375 moles NaOH x 1 mole NaOH/1 mole HCl = .375 mole HCl; .375 mole HCl/1.0M NaOh = .375; .375L = 375mL)
500
Explain how a flame will release light and the reason for which the color may be different.
What is when an electron goes from a high level to a low level, it releases photons of light. Colors are generated from the specific wavelengths and absorption of light of specific wavelengths from numerous photons. The color for each element is defined by the line emission spectrum.
500
Devise a procedure in which 1L of 0.5M NaCl solution is formed.
What is
1. Weigh 29.22g of NaCl. (58.44g/mol x 0.5M)
2. Place the NaCl in a volumetric flask (1L).
3. Gradually add distilled water to dissolve the salt.
4. Fill the flask until it reaches the 1L point.
500
A student is given 3.00g of a mixture containing anhydrous MgCl2 and KNO3. To determine the percentage by mass of MgCl2, the student uses excess AgNO3 to precipitate the chloride ion. The mass of the AgNO33.7%3 precipitate is 6.07g. What is the percent by mass of MgCl2 in the original mixture?
What is 67.3%
6.07g / 143.32 g/mol AgNO3 = 0.0424 mol AgNO3
0.0424 mol / 2 mol Cl = 0.0212 mol MgCl2
0.0212 mol x 95.20 g/mol = 2.02 g MgCl2
2.02 / 3.00 g x 100 = 67.3%
500
A 2.05 gram sample of benzoic acid reacted in a calorimeter. The heat capacity of the calorimeter was 11.0 kJ K. The heat of reaction of benzoic acid is -3300 kJ mol. What is the change in internal energy during this reaction?
~molar mass benzoic acid = 122.1 g/mol
~2.05g benzoic acid/122.1g = 0.0168 mol C7H6O2
~-3300 kJ are released for every 1 mol
~-3300 x 0.0168 = -55.44 kJ