Chem Lab Exam 2
When testing the pH of a solution with pH paper, dip _________ in the solution. Add a _______ of the solution to the paper. Compare the _____ of the pH paper to the scale that appears on the container.
1. Stiring Rod 2. Drop 3. Color
When taking a measurement with a pH meter, keep the instrument in the _______1_________ until it is needed. Rinse the pH meter with _______2_______ and gently pat dry. Place the meter in the sample solution, and record the measurement when the pH _________3_________.
1. Storage Solution 2. Deionized water 3. Stabilizes
When diluting acid with water, it is important to always add the ______________ to the ______________.
1. acid 2. water
Unlike a strong acid, a weak acid ____________ Thus, the weak acid disassociation is considered _______________.
1. does not dissociate completely 2. Reversible
C2H6 + O2 --> CO2 + H2O
2C2H6+7O2⟶4CO2+6H2O
Erlenmeyer flask
For heating and holding reactions
test tube holder
Holds test tubes
test tube rack
Holds test tubes
Molarity equation
M=n/v n=Moles of solute v= liters of solution
Conductivity NaCl, AlCl3, and CaCl2
NaCl - lowest CaCl2 - Medium AlCl3 - Highest
non-electrolyte, Weak electrolyte, or strong electrolyte? O2
Non-electrolyte
Contains a complete solution
Non-electrolyte Solute
Has little or no Conductivity
Non-electrolyte Solution
Identify the products for the reaction of lead(II) nitrate (Pb(NO3)2) and potassium iodide (KI)
PbI2 and K(NO3)
The ferric chloride test shows the presence of __________
Phenols
Identify the reagents that are used in the synthesis of aspirin.
Phosphoric Acid Salicylic Acid Acetic Anhydride
non-electrolyte, Weak electrolyte, or strong electrolyte? H2CO3
Weak Electrolyte
Has a medium level of conductivity
Weak electrolyte solution
Determine when you should remove your goggles in the lab room.
When everyone in the room is done handling any chemicals or glassware.
Can Iron(III) chloride be used to assess the purity of aspirin synthesized from salicylic acid?
Yes!
Parts per million (ppm)
You want to measure a very small, trace element in water.
molality (m)
You want to study the impact of the solute on the solvent's properties.
Molarity (M)
You want to study the reaction between two solutes when mixing their solutions.
[2]C2H2+C2H2+ [5] O2⟶O2⟶ [4] CO2+CO2+ [2] H2OH2O
[2]C2H2+C2H2+ [5] O2⟶O2⟶ 4 CO2 + 2 H2O
electronic balance
a balance that measures mass automatically
volatile
a characteristic that describes substances that evaporate readily, and produce large amounts of vapors
Hot plate
a lab tool used to heat substances
test tube
a thin glass tube closed at one end, used to hold small amounts of material for laboratory testing or experiments.
The difference between the solutions is a concentration and volume change by 10%. Why does the difference in pH make sense for this difference? a. The pH is logarithmically related to concentration of H3O+. b. The pH is linearly related to concentration of H3O+. c. The pH is inversely proportional to the volume of the solution. d. The pH increases as the volume of the solution increases.
a. The pH is logarithmically related to concentration of H3O+.
Law of Conservation of Matter
atoms of matter are not created or destroyed during a chemical reaction.
Which change to the coffee solution changed the pH of the solution? a. Adding more coffee to the coffee initially in the container. b. Adding more water to the coffee in the container. c. Draining some of the coffee solution from the container. d. All the changes to the solution changed the pH.
b. Adding more water to the coffee in the container.
A cleaning product company is having trouble with the pH control of one of their products. The product should be slightly basic but the pH is too high. What could the company try to correct the pH of the product? a. Increasing the amount of product in each container. b. Diluting the contents of each container by adding water. c. Allowing some water to evaporate from each container. d. Adding drain cleaner from this activity to each container.
b. Diluting the contents of each container by adding water
To increase the pH of the solution, did you need to add more drain cleaner or more water and why? a. More drain cleaner needed to be added because drain cleaner is more acidic than water. b. More drain cleaner needed to be added because drain cleaner is more basic than water. c. More water needed to be added because the drain cleaner needed to be more concentrated. d. More water needed to be added because the drain cleaner needed to be more dilute.
b. More drain cleaner needed to be added because drain cleaner is more basic than water.
Did the same change(s) affect the pH for drain cleaner as they did for coffee and why? a. The same change(s) affected the pH because pH does not depend on the identity of the solute. b. The same change(s) affected the pH because changing the concentration affects the pH for any acidic or basic solution. c. Different change(s) affected the pH because different solutes behave completely differently. d. Different change(s) affected the pH because volume affects basic solutions differently than acidic solution.
b. The same change(s) affected the pH because changing the concentration affects the pH for any acidic or basic solution.
Select the statement that best answers the following question Can you determine the pH of a solution by knowing only the pOH for a solution? a. Yes, because the product of pH and pOH is constant. b. Yes, because the sum of pH and pOH is constant. c. No, because pH and pOH relate to two different ions. d. No, because pH and pOH are not related.
b. Yes, because the sum of pH and pOH is constant.
Suppose this lab allowed you to mix two of the solutions. What type of solution would you expect to result from mixing the drain cleaner with the battery acid? a. A strongly acidic solution would result. b. A strongly basic solution would result. c. A solution near neutral would result. d. Two layers of different pH would result.
c. A solution near neutral would result.
What is the best definition of an acid with the characteristics from the table? a. An acid has a high pH and more H3O+ than OH− present in solution. b. An acid has a high pH and more OH− than H3O+ present in solution. c. An acid has a low pH and more H3O+ than OH− present in solution. d. An acid has a low pH and more OH− than H3O+ present in solution
c. An acid has a low pH and more H3O+ than OH− present in solution.
What is the relationship between [H3O+] and [OH−] for the solutions? a. The product of [H3O+] and the [OH−] is greater for a solution with a higher pH. b. The product of [H3O+] and the [OH−] is lower for a solution with a higher pH. c. The product of [H3O+] and the [OH−] is constant for any pH. d. The product of [H3O+] and the [OH−] is not predictable, even if you know the pH.
c. The product of [H3O+] and the [OH−] is constant for any pH.
Oxygen (O2)
is a colorless, odorless gas that supports combustion. A glowing wooden splint will brighten or burst into flames when inserted into a container.
bumping
liquid boils out of the container
evaporating dish
liquids are heated over a flame so that they evaporate, leaving a solid residue
ring stand and ring
metal rod upright heavy base a support with many uses
Examples of solution
mouth wash rubbing alcohol sanitizing chemicals in a pool vinegar tea
non-electrolyte, Weak electrolyte, or strong electrolyte? C
non-electrolyte
Spatula
small scoop used to transfer powder and crystal chemicals
pH strips
test a substances' acidity (1 (acidic)-14 (basic))
Work surface
the horizontal, flat area in a fume hood upon which experiments are carried out.
Degassing
the removal of dissolved gases from liquids.
Watch Glass
to hold solids while being weighed, or as a cover for a beaker
glass stirring rod
to mix or stir substances; made of glass to resist heat, stains, corrosion
Sidearm flask
triangular flask with a side jet to assist in vacuum filtration (always used with a Buchner funnel)
Bunsen burner
used to heat substances
striker
used to light bunsen burner
Dropper
used to move small amounts of liquids or to measure volume by counting drops
wire gauze
used to support a container (such as a beaker or flask) during heating
Contains a partially dissociated solute
weak electrolyte solution
Composition (Combination) Reaction
𝐀 + 𝐁 ⟶ 𝐀𝐁 2 reactants 1 product
percent by mass for a solution
% mass of a solution= Mass of Solute/Mass of Solution x 100
percent mass of a solution
% mass of solution = mass of solute/mass of solution x 100
Percent recovery formula
(Product mass)/(initial mass) x 100
In the experiment, the Synthesis and Analysis of Aspirin, which steps need to be carried out in the fume hood?
- Adding salicylic acid and acetic acid together. - adding 5 drops of phosphoric acid to the flask with salicylic acid and acetic acid - measuring out acetic anhydride -loosely capping the flask with the reaction mixture before it is heated.
What is the pOH of a 0.41 M KOH solution?
0.39
What is the pH of a 0.38 M HCl solution?
0.42
Once the vacuum filtration set-up is complete, start by ______ in the filter funnel. Then, _______ ine the mixture ___________________.
1. Adding a small amount of water 2. Slowly decant 3. In the MIDDLE of the funnel paper
Iron(III) chloride can be used to assess the purity of aspirin synthesized from salicylic acid. Iron(III) chloride ______ react with aspirin because the reaction requires ____ which is present in ______
1. Does not 2. phenolic Functional Group 3. Salicylic Acid and not Asprin.
what can understanding concentration help you do?
1. Provide the correct amount of medication in a liquid medicine 2. Control the amount of sanitizing chemicals in a pool.
spot well plate
Used for holding several substances at once
Aspirin can be prepared from salicylic acid (C7H6O3C7H6O3), which has a molar mass of 138.12 g/mol, and acetic anhydride (C4H6O3C4H6O3), which has a molar mass of 102.04 g/mol. The density of acetic anhydride is 1.082 g/mL. C7H6O3+C4H6O3⟶C9H8O4+C2H3O2C7H6O3+C4H6O3⟶C9H8O4+C2H3O2 What is the theoretical yield of aspirin (C9H8O4C9H8O4), which has a molar mass of 180.15 g/mol, possible when reacting 3.10 g of salicylic acid with 3.73 mL of acetic anhydride?
4.04 g⟶mol⟶mol⟶g (Go back and look at prelab quiz if extra help is needed) (The formula is also listed on the questions and problems worksheet)
Sulfuric acid, H2SO4H2SO4, is an important industrial chemical, typically synthesized in a multi-step process. What is the percent yield if a batch of H2SO4H2SO4 has a theoretical yield of 3.7 kg, and 2.6 kg are obtained at the end of the process?
70.72% 2.6kg/3.7kg x 100
cold water bath
????
Single Replacement Reactions
A + BC ⟶ B + AC element + compound ⟶ Element + compound
Solute
A chemical that is dissolved
A positive ferric (phenols) chloride test appears as _______
A color change to purple
A negative ferric (no phenols) chloride test appears as ______
A colorless solution
Solution
A liquid consisting of one substance dissolved in another
Solvent
A liquid that dissolves another substance
concentration
A value used to describe the amount of one substance dissolved in another
Double Replacement Reactions
AB + CD ⟶ AD + CB 2 compounds + 2 New Compounds
Decomposition Reactions
AB ⟶ A + B 1 reactant 2 products
Beaker
An open cylindrical container with a pouring lip; used for mixing larger amounts of substances
When working in a fume hood, what is the best position of the hood sash?
As low as possible, no more than halfway up
When is the best time to clean glassware during the lab session?
As soon as practical after use.
Acid or Base? Ba(OH)2 RbOH HNO2 HClO4 KOH
Ba(OH)2 - Base RbOH - Base HNO2 - Acid HClO4.- Acid KOH - base
Combustion Reactions
C_H_ + O2 ⟶ xCO2 + H2O Fuel + Oxygen ⟶ Carbon Dioxide + Water
Physical Change
Change in state Change in size Tearing apart Breaking into pieces Grinding into powder Dissolving
Decomposition Example using copper
Cu(OH)2(s)Δ−→CuO(s)+H2O(g)
Low conductivity --> Highest Conductivity
Deionized Water --> Fresh water --> Brackish water --> Seawater
observation of conductance: nolight, red light only, red and green light
Distilled water --------- No light Soap -- ---------------- No light C12H22O11 (sucrose) -- No light HCl -------------------- Red/Green lights Ethanol (alcohol) ------ Red light NaOH ------------------ Red/Green lights Vinegar ---------------- Red light Ammoniac ------------- Red light Gatorade -------------- Red/Green lights Pedialyte --------------- Red light only
pH of different solutions
Drain cleaner 13.00 Hand soap 10.00 Blood 7.40 Spit 7.40 Water 7.00 Milk 6.50 Chicken Soup 5.80 Orange Juice 3.50 Soda pop 2.50 Vomit 2.00 Battery Acid 1.00
Which types of hazards can a fume hood help protect the user against?
Explosions, Fires, and Fumes
Glucose (molar mass=180.16 g/mol) is a simple, soluble sugar. Glucose solutions are used to treat patients with low blood sugar. Suppose you prepare a glucose solution using the described procedure. Step 1: Dissolve 247.5 g of glucose in enough water to make 500.0 mL of solution. Step 2: Transfer 22.2 mL of the solution to a new flask and add enough water to make 250.0 mL of dilute solution. What is the molar concentration of the glucose solution at the end of the procedure? use M1V1=M2V2
Step 1 convert the given grams to moles =1.374 moles of glucose convert ml to L 500ml = .5 L divide the moles of sugar by the volume of solution in liters to calculate the molarity of the solution in Step 1 =2.748 Step 2 (2.748 molarity) (22.2 ml) = M2 (250.0 ml) M2 =0.244
non-electrolyte, Weak electrolyte, or strong electrolyte? MgCl2
Strong Electrolyte
non-electrolyte, Weak electrolyte, or strong electrolyte? NaCl
Strong Electrolyte
Contains a completely dissociated solute
Strong Electrolyte Solution
non-electrolyte, Weak electrolyte, or strong electrolyte? (NH4)3PO4
Strong electrolyte
Has the highest conductivity
Strong electrolyte solution
Chemical Changes
Temperature increase* Formation of gas bubbles* Permanent color change Formation of precipitate Odor change Change in pH
Actual Yield
The amount of product experimentally produced
theoretical yield
The calculated amount of product under ideal conditions.
Percent Yield
The comparison of the experimental amount of product to the calculated amount
Why do you need to support a vacuum filtration apparatus with a clamp?
The filter funnel makes the apparatus top-heavy.
Airfoil
The front vent of a fume hood, which helps maintain proper air circulation.
Sash
The glass panel in front of the fume hood that shields the user from fumes and other hazards
supernatant
The liquid on top of the material deposited by settling or centrifugation.
Decanting
The process of separating a liquid/solid mixture by slowly pouring the liquid component into a new vessel as the solid settles to the bottom of the original vessel.
How should the mass of copper metal at the end of the reactions compare to the starting mass of copper?
The produced mass of copper should equal the starting mass of copper.
What does a percent recovery of more than 100% likely indicate?
The product still contains some water.
What is the purpose of stirring a solution while it is being heated?
To help evenly distribute heat throughout the solution
ring stand
Used as a support; Rings and clamps attach to the stand
To increase the pH of the solution, did you need to add more coffee or more water and why? a. More coffee needed to be added because coffee is more acidic than water. b. More coffee needed to be added because coffee is more basic than water. c. More water needed to be added because the coffee needed to be more concentrated. d. More water needed to be added because the coffee needed to be more dilute
d. More water needed to be added because the coffee needed to be more dilute
Buchner funnel
filters solids from liquids using a mild vacuum
hot water bath
in the science laboratory, usually a large beaker of water heated on a hot plate; used to heat test tubes that contain a flammable liquid such as alcohol
graduated cylinder
instrument used to measure volume of a liquid
Hydrogen (H2)
is a colorless, odorless gas that burns in air. Hydrogen is less dense than air that can be captured in an inverted vessel, or in a test tube with a paper towel plug. A mixture of hydrogen and air in a test tube will burn with a "pop" when exposed to a lit wooden splint.
Carbon dioxide (CO2)
is a colorless, odorless gas that does not burn in air or support combustion. For that reason, it is used to extinguish fires. When dissolved in water, it forms a mildly acidic solution containing carbonic acid, H2CO3(aq). A lit wooden splint will go out when inserted into a container of carbon dioxide.
