Chemistry Lab Midterm
7.32 x 10^-4
0.000732
4.65 x 10^-3
0.00465
How many kilometers is 2013.5 cm?
0.020135 km 2013.5 cm x (1 x 10^-2) m/1 cm x 1km/(1X10^3) m = 0.020135 km
How many liters is 32.5 mL?
0.0325 liters 32.5 mL x (1 x 10^-3) L/ 1 mL = 0.0325 liters
A block has a mass of 4.465 g and a volume of 132.8 cm3. Calculate the density in g/cm3.
0.03362 g/cm3 d = m/v d = 4.465 g/132.8 cm3
Predict the products of hydrochloric acid reacting with zinc metal.
1. ZnCl2 2. H2 The balanced equation is: Zn + 2HCl -> ZnCl2 + H2
Identify the common indicators that a chemical reaction has occurred.
1. a color change 2. precipitate being formed 3. a change in temperature 4. bubbles being produced
Fill in the words to complete each step in liquid spill cleanup. 1. Surround the area with BLANK, then cover the spill. 2. Scoop up the material and place in a BLANK. 3. Place the bagged waste in a BLANK. 4. Wipe down the area with BLANK.
1. absorbent material 2. plastic bag 3. solid waste container 4. detergent and water
What parts are present in every chemical equation?
1. an arrow 2. at least one product 3. at least one reactant
A BLANK is a number to the left of a formula and it applies to BLANK.
1. coefficient 2. the entire formula it precedes
In the context of a balanced chemical equation, a BLANK is a number to the lower right of an element or ion within formula and it applies to BLANK.
1. subscript 2. only the part of the formula it follows
A 2.67 g piece of zinc (density = 7.14 g/mL) is added to a graduated cylinder that contains 12.13 mL H2O. What will be the final volume reading on the graduated cylinder, in mL?
12.50 v = m/d v = 2.67 g/7.14 g/mL = 0.3739 + volume of water 12.13 mL
Suppose you are titrating an acid of unknown concentration with a standardized base. At the beginning of the titration, you read the base titrant volume as 2.61 mL. After running the titration and reaching the endpoint, you read the base titrant volume as 15.17 mL. What volume, in mL, of base was required for the titration?
12.56 mL To find the volume of titrant used in any titration, subtract the starting volume reading from the final volume reading.
A graduated cylinder contains 10.00 mL water. A 14.74 g piece of aluminum is added to the water, and the volume rises to 15.46 mL. What is the density of the aluminum in g/mL?
2.70 g/mL d = m/v d = 14.74 g/5.46 mL = 2.70 g/mL
Knowing that one day is 24 hours, how many days is 66.9 hours?
2.79 days 66.9 x 1 day/24 hours = 2.79 days
Balance C2H2 + O2 -> CO2 + H2O
2C2H2 + 5O2 -> 4CO2 + 2H2O
Balance C2H6 + O2 -> CO2 + H2O
2C2H6 + 7O2 -> 4CO2 + 6H2O
Magnesium + oxygen equation
2Mg + O2 -> 2MgO(s)
A 24.5 g sample of solution has a density of 0.768 g/mL. What is the sample volume (in mL)?
31.9 mL v = m/d v = 24.5g/0.768 g/mL = 31.9 mL
How many oxygen atoms are in four unit of Ca3(PO4)2?
32 atoms 1 unit has O: 4 x 2 = 8 So, 4 units has 8 x 4 = 32
A series of measurements in the lab led to an experimental result of 32.9 mL, with a calculated standard deviation of 0.3 mL. What is the standard way to report this result?
32.9 +- 0.3 mL
In a technique to separate 3.1502 grams of a combined sample of SiO2, NH4Cl, and NaCl, none of the sample was lost. What is the percent recovery of NaCL if at the end of the separation process, 0.6215 grams of SiO2 and 1.4005 grams of NH4Cl were recovered?
35.81% original mass: 3.1502 g mass of SiO2 + NH4Cl = 0.6215 g + 1.4005 g = 2.022 g mass of NaCl = original mass - 2.022 g --> 3.1502 g - 2.022 g = 1.1282 g To find the percent recovery: % recovery of NaCl = (1.1282/3.1502) x 100% = 35.81%
Identify the section in which each type of information can be found on a Safety Data Sheet. recommended personal protective equipment (PPE)
Exposure Controls/Personal Protection
Identify the section in which each type of information can be found on a Safety Data Sheet. recommendations in case of accidental contact with the chemical
First Aid Measures
What practice will not help you make an accurate volume reading on a buret at the beginning of a titration?
Make sure that the meniscus starts exactly at 0.00 mL
After clamping a buret to a ring stand, you notice that the set-up is tippy and unstable. What should you do to stabilize the set-up?
Move the buret clamp to a ring stand with a larger base.
When sodium chloride is mixed with silver nitrate, what is or are the products?
NaCl + AgNO3 -> NaNO3 + AgCl Because NaCl + AgNO3 + - + - So, Na goes with NO3 & Ag goes with Cl.
Sodium bicarbonate + hydrochloric acid equation
NaHCO3 + HCl -> NaCl + CO2 + H2O
Most laboratory chemical spills are cleaned up in a similar manner, but acid and base spills require an extra step. What is this extra step?
Neutralize the spill before cleaning it up.
Potassium iodide + lead (II) nitrate equation
Pb(NO3)2 + KI -> PbI2 + 2KNO3
A football field is 120 yards by 53.333 yards. What is the area of the football field in acres if 1 acre=43560 ft2? Use correct significant figures when answering this question.
Solution: 1.3 Convert yards to feet: 120 yds x 3ft/1yd = 360 ft 53.333 yds x 3ft/1yd = 159.9999 ft Find the area in feet: 360 ft x 159.9999 ft = 57596.4 ft^2 Then, convert to acres: 57596.4 ft^2 x 1 acre/43560 ft^2 = 1.32223 acres Only two sig figs in 120 yards so 1.3 acres
a. funnel b. primary container c. waste label d. secondary container
Using the letters on the image, identify each component of the liquid waste set-up.
40.5 mL
What is the correct reading for the graduated cylinder in the close-up?
40.5 mL Note that volume markings increase going up the graduated cylinder. Therefore, with the meniscus above the 40 mL line, the correct volume is slightly greater than 40 mL. The bottom of the meniscus falls right in the middle of the space between the tick mark for 40 mL and 41 mL. Therefore, a good estimate of the volume is 40.5 mL.
What is the correct reading for the graduated cylinder in the close-up?
39.95 mL Note that volume markings increase going down the buret. Therefore, with the meniscus above the 40 mL line, the correct volume is less than 40 mL. The bottom of the meniscus falls right in the middle of the space between the tick mark for 39.9 mL and 40.0 mL. Therefore, a good estimate of the volume is 39.95 mL.
What is the correct reading of the volume in the pictured buret?
15.60 cm
What is the correct way to report the length of the rectangle in centimeters?
Name the compound Zn3(PO4)2
Zinc (II) Phosphate
Zinc metal + hydrochloric acid equation
Zn + HCl -> ZnCl2 + H2
Identify the precautions to take with exits in the lab. Select one or more: a) Do not block a door with an EXIT sign. b) Keep the exit door locked at all times. c) Locate the exits prior to the start of lab. d) Make sure lab windows are always open.
a) Do not block a door with an EXIT sign. c) Locate the exits prior to the start of lab.
Which types of signs are posted to convey information about chemical storage? Select one or more: a) Hazard signs such as "Flammable," "Oxidizer," and "Corrosive" b) National Fire Protection Association (NFPA) diamond c) Gas Cylinder sign d) Exit sign e) Safety equipment signs such as "Safety Shower" and "Eyewash Station"
a) Hazard signs such as "Flammable," "Oxidizer," and "Corrosive" b) National Fire Protection Association (NFPA) diamond c) Gas Cylinder sign
Which signs are typically posted in areas of active lab work? Select one or more: a) Personal protective equipment (PPE) sign b) Safety equipment signs c) Chemical storage signs d) Sign prohibiting food and drink
a) Personal protective equipment (PPE) sign b) Safety equipment signs c) Chemical storage signs d) Sign prohibiting food and drink
In general, which characteristics are necessary for a location to be suitable for chemical storage? Select one or more: a) dark b) poorly-ventilated c) dry d) cool e) warm
a) dark c) dry d) cool
Identify tools that are ideal for cleaning glassware.
brushes & detergent and water
Identify the types of information that are necessary to communicate with emergency responders. Select one or more: a) The history of safety incidents in the lab b) How the incident happened c) Any chemicals involved in an incident d) Any other hazards present in the lab
c) Any chemicals involved in an incident d) Any other hazards present in the lab
Under what conditions should a student inform the instructor of a lab injury? Select one: a) The instructor should be alerted only if the lab injury appears different from injuries the student has experienced previously. b) The instructor should be alerted only if the injury involves broken skin. c) The instructor must be informed of all laboratory injuries. d)The instructor needs to be alerted only if he or she needs to call 911.
c) The instructor must be informed of all laboratory injuries.
Name the compound CF4
carbon tetrafluoride
Potassium thiocyanate + iron (III) nitrate proof of reaction
change in color - when mixed the solution becomes dark red color and resembles fake blood
Potassium iodide + lead (II) nitrate proof of reaction
change in color and production of a precipitate (ppt); when liquids are mixed a bright yellow substance is produced
A precipitate is formed from two solutions.
chemical change
A solution heats up upon mixing with another.
chemical change
Bubbles are produced upon mixing two solutions.
chemical change
The color of a substance changes over time.
chemical change
Mixtures are characterized by two fundamental properties: 1. Each of the substances in the mixture retains its BLANK identity. 2. Mixtures are separable into these components by BLANK means.
chemical; physical
Only BLANK should be added or changed when balancing chemical equations.
coefficients
Potassium thiocyanate (KSCN) appearance
colorless liquid
hydrochloric acid appearance
colorless, liquid
What are the substances making up a mixture called?
components
Identify each described physical separation technique. A liquid is carefully poured out, leaving the solid behind in the container.
decantation
This is the process of separating a liquid from a solid (sediment) by gently pouring the liquid from the solid so as not to disturb the solid.
decantation
Name the compound N2O3
dinitrogen trioxide
How can a solid dissolved in water be separated from the water?
evaporation
Identify each described physical separation technique. A solvent is added to dissolve only one mixture component and then the liquids are separated.
extraction
Which process is used to separate soluble compounds from insoluble compounds?
extraction
Identify the safety equipment designed to deal with each emergency listed. Choices: first aid kit fire extinguisher fire blanket eyewash station safety shower chemicals in eyes
eyewash station
Identify each described physical separation technique. A solid is caught on paper or a membrane while the liquid passes through.
filtration
This is the process of separating a solid from a liquid by means of a porous material.
filtration
Identify the safety equipment designed to deal with each emergency listed. Choices: first aid kit fire extinguisher fire blanket eyewash station safety shower fire on a person
fire blanket
Identify the safety equipment designed to deal with each emergency listed. Choices: first aid kit fire extinguisher fire blanket eyewash station safety shower large fire on the benchtop
fire extinguisher
Identify the safety equipment designed to deal with each emergency listed. Choices: first aid kit fire extinguisher fire blanket eyewash station safety shower cute or minor burns
first aid kit
Magnesium Mg appearance
flat dull silver ribbon
Zinc metal + hydrochloric acid proof of reaction
gas produced - bubbles are produced in the test tube and zinc color changes and becomes darker/black
Sodium bicarbonate + hydrochloric acid proof of reaction
gas produced only
Capable of measuring a range of volumes of liquid
graduated
Which procedure cannot be performed on a hot plate, requiring a Bunsen burner instead?
heating a crucible to remove water from a hydrate
What are minor components in a mixture called?
impurities
When a vinegar and oil salad dressing separates into two layers, the oil floats on top of the vinegar. The density of the oil BLANK the density of the vinegar.
is less than
Pb(NO3)2 appearance
liquid and colorless
KI appearance
liquid and pale-yellow to colorless color
Which of the following would not be helpful in separation a mixture of sand and salt?
magnet
Most of the BLANK people encounter in everyday life consists of BLANK of different substances.
matter; mixtures
Determine the relative order of the metric prefixes of kilo-, micro-, centi-, and milli-.
micro- 10^-6 milli- 10^-3 centi- 10^-2 kilo- 10^3
BLANK are combinations of two or more substances.
mixtures
Is this an example of combustion? 2N2O5 -> 4NO2 + O2
no
Is this an example of combustion? CO2 + 4H2 -> CH4 + 2H2O
no
Iron (III) nitrate Fe(NO3)3 appearance
orange-yellow liquid
Name the compound PCl3
phosphorus trichloride
A liquid freezes into a solid.
physical change
A solid dissolves into water.
physical change
The separation of the components of a mixture is based upon the fact that each component has different BLANK properties. The components of a mixture are separated based on their BLANK properties.
physical; physical
Magnesium + oxygen proof of reaction
production of light - bright white light is produced, and Mg ribbon turns to black ash
When BLANK substances have BLANK compositions, the composition of BLANK can vary.
pure; fixed; mixtures
Identify the safety equipment designed to deal with each emergency listed. Choices: first aid kit fire extinguisher fire blanket eyewash station safety shower chemicals on clothes
safety shower
Zinc metal appearance
silver chunk, with rugged edges
Sublimation is a phase change from BLANK to BLANK. The BLANK phase is not present in this change.
solid; gas; liquid
Identify each described physical separation technique. A solid mixture is heated. One component transitions directly between solid and gas.
sublimation
press the BLANK button to cancel out mass on a balance
tare/zero
The composition of homogeneous mixtures is ______________.
uniform
The composition of heterogeneous mixtures is ______________.
variable
Designed to measure one specific volume of liquid & Used for applications in which great accuracy is needed
volumetric
Sodium bicarbonate appearance
white powdery solid
Is this an example of combustion? 2C2H6 + 7O2 -> 4CO2 + 6H2O
yes
Is this an example of combustion? 2NO + O2 -> 2NO2
yes
Is this an example of combustion? C + O2 -> CO2
yes
percent error formula
|accepted value-measured value| / accepted value x100
Changing gloves often will minimize the spread of chemicals. To properly remove gloves, first, BLANK, and then, BLANK. Then insert BLANK between the interior edge of the second glove and the skin, and remove the second glove.
1. grasp the exterior of one glove with a gloved hand 2. peel off the first glove 3. a bare finger
It is often helpful to remember the acronym PASS when using a fire extinguisher. Fill in the word that corresponds with each letter to complete the steps needed for operation of this device. 1. BLANK the pin. 2. BLANK the nozzle at the base of the fire. 3. BLANK the lever slowly. 4. BLANK the spray from side to side over the fire.
1. pull 2. aim 3. squeeze 4. sweep
When heating a solution to boiling on a hot plate, start by BLANK. Then, turn the heat to BLANK to start. If necessary, BLANK after waiting about 10 minutes without seeing boiling.
1. starting and stabilizing the stir function 2. a medium heat setting 3. turn up the heat setting
4.65 x 10^3
4650
Convert 6.5 mm to nm
6.5mm x 1m/1000mm x 10^9nm/1m = 6,500,000 nm = 6.5 x 10^6 nm
7.32 x 10^6
7320000
Zinc metal + hydrochloric acid what is the gas?
H2
Identify the section in which each type of information can be found on a Safety Data Sheet. incompatibility or reactivity with other chemicals
Handling and Storage
Identify the section in which each type of information can be found on a Safety Data Sheet. possible dangers and health effects
Hazards Identification
Identify the section in which each type of information can be found on a Safety Data Sheet. chemical name and formula
Identification
Potassium thiocyanate + iron (III) nitrate equation
KSCN + Fe(NO3)3 -> FeSCN2+
