Midterm Lab

What is the oxidation number for copper in CuSO4?

+2

What is the first step for response to an emergency situation?

Remain calm and quiet, gather information, and assess the situation.

What should you do every time before you leave the lab?

Remove your gloves. Remove your labcoat, if you are wearing one. Wash your hands.

Choose the best graduated cylinder to make each measurement in a single use. 18.5 mL of a NaClNaCl solution 36 mL of water 5.75 mL of a sucrose solution

a 25 mL graduated cylinder with markings every 1 ml a 50 mL graduated cylinder with markings every 10 ml a 10 mL graduated cylinder with markings every 0.1 ml

When describing the uncertainty of a measurement, the term ___ refers to the closeness between a measurement and its accepted value, whereas the term ___ refers to the closeness among a set of measurements.

accuracy precision

If you drop or break glassware in lab, first ___ . Then, ___. Finally, place all that material into the ___.

get thick gloves or dustpan carefully collect all the broken glassware broken glass container

Calculate the moles of ammonia present in a 5.141 g sample if the molar mass of ammonia is 17.030 g/mol.

0.3019

1. Surround the area with ____, then cover the spill. 2. Scoop up the material and place in a ___. 3. Place the bagged waste in a ___. 4. Wipe down the area with ___.

1. absorbent material 2. plastic bag 3. solid waste container 4. detergent and water

Suppose you are performing an experiment in which you produce a solid and measure its mass. You run the six trials reported in the table to find the best average mass of the product. Trial number Mass of product 11.67 g1.67 g21.74 g1.74 g31.95 g1.95 g42.08 g2.08 g52.43 g2.43 g61.07 g1.07 g What is the average mass, in grams, of the product based on the six trials? Type answer:

1.82

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

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 1.94 mL. After running the titration and reaching the endpoint, you read the base titrant volume as 23.82 mL. What volume, in mL, of base was required for the titration?

21.88

The lab experiment introduces you to the chemistry of elemental copper. Copper will undergo several chemical transformations, represented by the chemical formulas given. What is the correct sequence of chemical transformations with the correct phases? Begin with 1 and and with 6. Cu(OH)2 (s) Cu(NO3)2 (aq) CuSO4 (aq) CuO (s) Cu (s) wire Cu (s)

3 2 5 4 1 6

What is the last step of any spill cleanup procedure?

Wipe down the affected area with detergent and water.

The cycle of copper reactions starts with solid copper metal and ends with solid copper metal. Suppose you start with 0.506 g of Cu. After performing all the reactions, you have 0.441 g of Cu. What percentage of the copper did you recover?

87.2

When drawing up liquid into a micropipette, put the tip in the liquid at a ___ degree angle, push the plunger to the ___ point of resistance, and then ___ the plunger. When dispensing that liquid from the micropipette, hold the micropipette at a ___ degree angle in the desired container and push the plunger to the ___ point of resistance. ___ the plunger until dispensing is done.

90 first release 45 second hold down

What information does not need to be included a chemical waste label?

A description of the experiment the chemicals were used for

Select the correct value for each letter to complete the formula for percent error. In order to calculate the percent error, you need to know the accepted value and the experimental value. A=|accepted value−B|C×100

A: percent error B: experimental value C: accepted value

What are the best practices while sharing a lab balance with other students? Select one or more:

Alert your TA or instructor about any issues with the balance. Brush off any chemical dust around the balance after each use.

What are the best practices for safely handling waste in the lab? Select one or more:

Always wear appropriate Personal Protective Equipment. Check labels or instructions before any disposal

When inputting a formula into Excel or other spreadsheet software, what components are required for the formula to function properly? Select one or more:

An equal sign at the beginning of the formula Closing parentheses for any opening parentheses

Identify the types of information that are necessary to communicate with emergency responders.

Any other hazards present in the lab Any chemicals involved in an incident How the incident happened

Determine when to put on disposable gloves for work in the lab.

Before handling any glassware or chemicals for the experiment

Which compounds could be represented by the empirical formula CH2? Select one or more:

C2H4 C3H6 C8H16

A 7.298 g sample of copper reacts with oxygen, forming a copper oxide. The final mass of the copper oxide is 8.217 g. What is the formula of the copper oxide?

Cu2O

When using a properly stabilized balance, how should you ensure that you get the most accurate mass reading possible?

Close the side shields on the balance during reading. Measure the mass of the sample at room temperature.

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

How do you determine the last digit in any measured number?

Estimate one digit past the smallest precisely known digit or marking.

Identify the recommended practices when putting a tip on a micropipette. Select one or more:

Gently push the micropipette into the tip and tap lightly to load the tip. Use the tip size designed for the micropipette size in use.

Which types of signs are posted to convey information about chemical storage?

Hazard signs such as "Flammable," "Oxidizer," and "Corrosive" National Fire Protection Association (NFPA) diamond Gas Cylinder sign

Identify the section in which each type of information can be found on a Safety Data Sheet. chemical name and formula recommended personal protective equipment (PPE) possible dangers and health effects recommendations in case of accidental contact with the chemical incompatibility or reactivity with other chemicals

Identification Exposure controls/personal protection Hazards identification First aid measures Handling and storage

Read the Safety Data Sheet (click SDS icon below) of hydrogen peroxide to identify the recommended way to store this substance.

In a tightly closed container in a dry and well-ventilated place

What information is needed in order to be prepared for an emergency?

Location of lab phone and first aid kit Location of all exits Contact information for emergency personnel Understanding of where to go should an emergency occur

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.

Identify the type of each reaction in the copper cycle. Cu(NO3)2 (aq) + 2NaOH (aq) --> Cu(OH)2 (s) + 2NaNO3 Cu (s) + 4HNO3 (aq) --> Cu(NO3)2 (aq) + 2NO2 (aq) + 2H2O (l) Cu(OH)2 (s) --> CuO (s) + H2O (g) CuO (s) + H2SO4 (aq) --> CuSO4 + H2O (l) CuSO4 (aq) + Zn (s) --> ZnSO4 (aq) + Cu (s)

Metathesis redox dehydration metathesis redox

___ are combinations of two or more substances.

Mixtures

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.

Pull the pin Aim the nozzle at the base of the fire Squeeze the lever slowly Sweep the spray from side to side over the fire

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.

Determine whether or not each chemical formula is an empirical formula. C6H12O6 K2C2O4 Ba3(PO4)2 NaMnO4 CaCO3

Not empirical not empirical empirical empirical empirical

Identify the equipment best suited for extinguishing each type of fire. Small benchtop fire Clothing fire Large fire on floor

Overturned beaker Fire blanket Large fire on floor

Review the Safety Data Sheet (SDS) (click the SDS icon below) for hydrogen peroxide, then identify the best course of action for each type of chemical exposure. In case of eye contact ___. If swallowed ___. In case of skin contact ____. If inhaled ___.

Rinse with water for 15 minutes. Rinse mouth with water. Take off any contaminated clothing and rinse thoroughly. Move person to fresh air.

Which steps are necessary for cleaning a spill involving broken glass?

Stop the spread of the spill. Soak up any spilled liquid with absorbent material. Pick up large pieces of glass with gloved hands.

Identify the following errors as systematic or random. A micropipet is improperly calibrated, and the balance dispensed is always smaller than expected. A few drops of water are on a balance pan, causing the mass output on the balance to be high each time it is used. The last digit on a pH meter fluctuates up and down as a measurement is taken. A thermometer is placed such that the bulb makes poor contact with the measured substance, giving erratic temperature readings.

Systematic systematic random random

In the reaction of magnesium metal with hydrochloric acid, how do you determine when the magnesium metal has reacted completely?

The magnesium metal is gone. Gas bubbles are no longer produced.

Read each statement regarding food and beverages in the lab and determine if each is true or false. Food items should not be brought into the lab. Chewing gum is okay in the lab as long as you don't blow bubbles. Beverages are allowed in lab as long as they are in containers with lids. Tobacco products of all kinds are prohibited in lab.

True False False True

In lab, you may need to evaluate the odor or smell of a chemical. What is the best way to smell a chemical sample?

Use your hand to gently waft the smell toward you.

Determine the safest option in the lab if you need your vision to be corrected.

Wear corrective glasses or lenses under your safety goggles for the whole experiment, but always check with your TA or Instructor for your school's policy

Determine when you should remove your goggles in the lab room.

When everyone in the room is done handling any chemicals or glassware

When should you start a new chemical waste container in the lab?

When the contents of the current container are a couple inches below the brim of the container

A lower case letter between parentheses and next to a molecular formula in a chemical reaction represents a physical state or phase of that substance. For example, H2SO4(aq) means that this substance is in the ___________________ state.

aqueous

Identify the phase of the copper product after each reaction in the copper cycle. The addition of HNO3 to Cu The addition of H2SO4 to CuO The addition of NaOH to Cu(NO3)2 The addition of Zn to CuSO4 The heating of Cu(OH)2

aqueous aqueous solid solid solid

Mixtures are characterized by two fundamental properties: Each of the substances in the mixture retains its ___identity. Mixtures are separable into these components by ___ means.

chemical physical

What are the substances making up a mixture called?

components

Suppose you are given the mass of each element in a compound sample. To calculate the empirical formula, start by ___ using ____. Then, ___ by ___.

converting the mass of each element to moles each element's molar mass calculate the ratio between the elements dividing the moles of each element by the smallest number of moles present

How can a solid dissolved in water be separated from the water?

evaporation

Determine whether each quantity is a measured value or an exact value. 1 ft = 12 in 18 meters 2 cups of milk 2 avocados 3 teacups 144 grams of sugar

exact measured measured exact exact measured

Which process is used to separate soluble compounds from insoluble compounds?

extraction

This is the process of separating a solid from a liquid by means of a porous material.

filtration

Match each lab incident to the item of PPE that will protect you from it. Each item of PPE will only be used once. While picking up a buret, an unknown solution left by a previous solution drips onto your hand. While transferring a solution from a flask to a beaker, the solution accidentally spills down the front of the lab bench. While checking on a stirring solution, the solution splashes up towards your face. While pulling an empty beaker off the shelf at the beginning of lab, it slips out of your hand onto the floor.

gloves lab coat goggles closed-toe shoes

Changing gloves often will minimize the spread of chemicals. To properly remove gloves, first, ____, and then, ___. Then insert ___ between the interior edge of the second glove and the skin, and remove the second glove.

grasp the exterior of one glove with a gloved hand peel off the first glove a bare finger

Systematic error is caused by ___, while random error is caused by

improper use of a measuring device random fluctuations in a measuring device

What are minor components in a mixture called?

impurities

Magnesium reacts with oxygen in the air when ___ . Unlike other reactions, you should not ___ this reaction

lit with a Bunsen burner look directly at

Which of the following would not be helpful in separation a mixture of sand and salt?

magnet

Most of the___ people encounter in everyday life consists of ___of different substances.

matter mixtures

Determine whether each practice is recommended to keep a micropipette clean and functioning properly. Place the micropipette on the bench between uses. Save tips after removal to reuse them later. Turn the micropipette upside down after loading with liquid. Use a new tip any time you change solutions. Place the micropipette on a rack after using it.

not recommended not recommended not recommended recommended recommended

The separation of the components of a mixture is based upon the fact that each component has different ___ properties. The components of a mixture are separated based on their___ properties.

physical physical

When using the Tare function on a balance, start by ___. Then, ___ to cancel out that mass. Finally, ___ and record the mass of your sample.

placing the glassware on the balance press the Tare/Zero button add your sample to the glassware

Whereas ___ substances have ___ compositions, the composition of ___ can vary.

pure fixed mixtures

Determine the best way to deal with each of the following items that may dangle into the way during lab work. long necklaces loose bracelets long hair long earrings flowy sleeve

remove remove tie back or secure remove tie back or secure

Determine where to dispose of each type of waste Syringe tips unused solid reagent broken flask titrant solution

sharps container solid waste container box lined with puncture resistant bag nalgene bottle with cap

Move to the safety shower if you spill hazardous chemicals on your ___. Stand under the shower and ___ the lever. Remove clothing and continue flushing the area for ___.

skin or clothing pull 15 minutes

Sublimation is a phase change from ___ to ___. The ___ phase is not present in this change.

solid gas liquid

Suppose that two students perform a titration experiment multiple times, resulting in the average concentrations reported here. Student A 0.125 ± 0.008 ' Student B 0.12 ± 0.03 M The more precise work was done by ___ because ___

student A that student's data has a smaller standard deviation

A solid mixture is heated. One component transitions directly between solid and gas. A solvent is added to dissolve only one mixture component and then the liquids are separated. A solid is caught on paper or a membrane while the liquid passes through. A liquid is carefully poured out, leaving the solid behind in the container.

sublimation extraction filtration decantation

Mass is conserved in an experiment if the___ of the individual component masses equals the mass of the ___

sum mixture of the components

To measure out a volume of liquid, start by choosing the appropriate graduated cylinder and moving the bumper to the ___of the graduated cylinder to protect it from breakage. Then, pour the liquid into the graduated cylinder until the ___ of the meniscus aligns with the desired volume marking when you look at the graduated cylinder from ___.

top bottom eye level

The composition of homogeneous mixtures is ______________.

uniform

The composition of heterogeneous mixtures is ______________.

variable

Determine whether each of the properties described applies to volumetric or graduated glassware. Used for applications in which great accuracy is needed Designed to measure one specific volume of liquid Capable of measuring a range of volumes of liquid

volumetric volumetric graduated

Which is NOT a good source of information about the hazards that affect waste disposal in a chemistry lab?

your lab partner