chem 1a labflow
Identify the meaning of each chemical equation symbol.
+ There are two separate substances on either the products side or the reactants side. Δ→ Heat is applied. ⟶ Substances on the reactants side are converted to the substances on the products side. (l) The substance is a liquid.
What is the freezing point (in degrees Celcius) of 4.11 kg of water if it contains 191.8 g of CaBr2? The freezing point depression constant for water is 1.86oC/m and the molar mass of CaBr2is 199.89 g/mol.
-1.30 calculate the moles of solute from the mass and molar mass of the solute and divide by the mass of water in kilograms. Substitute these values into the equation for freezing point depression. ΔTf=3×1.86∘C/m×m
suppose you are titrating a sulfuric acid solution of unknown concentration with a sodium hydroxide solution according to the equation H2SO4 + 2NaOH -> 2H2O +Na2SO4 if you require 25.42 mL of .604 M NaOH solution to titrate 196.5 mL of H2SO4 solution, what is the concentration of the H2SO4 solution?
.0391
How many kilometers is 4190.3 cm? Type answer:
.04190
What is the value of the gas constant, R, in units of L⋅atm/mol⋅K? Report the value with at least three significant figures.
.08206
How many moles of H2 can be formed if a 2.25 g sample of Mg reacts with excess HCl?
.093 2.25 g Mg× (1 mol Mg/24.3 g Mg)×(1 mol H2/1 mol Mg)
how many grams of KOH are needed to neutralize 14.8 mL of .18 M HCl in stomach acid?
.146 g
Calculate the moles of ammonia present in a 3.067 g sample if the molar mass of ammonia is 17.030 g/mol.
.1801 moles of substance=mass in g×1 molE of substance/molar mass
If the freezing point depression for a solution is 2.5°C and Kf = 4.5°C/m, what is the molality of the solution?
.56m divide temperature by Kf
Select the coefficients necessary to balance each equation. Choose a coefficient for every compound.
1,1,1 3,2,1,6
Fill in the words to complete each step in liquid spill cleanup.
1. absorbent material 2. plastic bag 3. solid waste container 4. detergent and water
a concentrated salt solution has a mass of 5.33g for a 5.00mL sample, what is the specific gravity of this solution?
1.066 specific gravity=density of substance/density of water
What mass, in grams, of NaCl needs to be added to 1.6 kg of water in order to create a solution with a freezing point of -5.6 °C? The freezing point depression constant of water is 1.86 ºC/m.
140 m=-(−5.6)∘C/ 1.86∘C/m×2 Multiply the molality by the number of kilograms of solvent to obtain the number of moles of NaCl, then multiply by the molar mass to obtain the answer in grams. m∗1.6kg∗58.44g
Suppose that you add 22.6 g of an unknown molecular compound to 0.250 kg of benzene, which has a Kf of 5.12oC/m. With the added solute, you find that there is a freezing point depression of 3.30oC compared to pure benzene. What is the molar mass (in g/mol) of the unknown compound?
140.37 m=ΔTf/iKf=3.30∘C/(1)(5.12∘C) divide the mass of the sample by the moles to find the molar mass.
What is the heat, q, in joules transferred by a chemical reaction to the reservoir of a calorimeter containing 105g of dilute aqueous solution (c=4.184 J/g⋅ºC) if the reaction causes the temperature of the reservoir to rise from 21.0 ºC to 25.0 ºC?
1757.28 q=mcΔT
a student performed a density experiment in triplicate and recorded the data shown. calculate the average density (in g/mL) for this experiment trial 1: 2.99 g/mL trial 2: 2.82 g/mL trial 3: 2.85 g/mL
2.89 g/mL sum the values and divide the sum by the number of values
calculate the mass percent of a vinegar solution with a total mass of 96.41 g that contains 2.80 g of acetic acid
2.904 % mass = mass of solute/mass of solution x 100
What information does not need to be included a chemical waste label?
A description of the experiment the chemicals were used for
Potassium hydrogen phthalate is
A primary standard
Determine whether each observation generally corresponds to a physical change or a chemical change.
A solution heats up upon mixing with another. Chemical change The color of a substance changes over time. Chemical change A precipitate is formed from two solutions. Chemical change A solid dissolves into water. Physical change A liquid freezes into a solid. Physical change Bubbles are produced upon mixing two solutions. Chemical change
When a known quantity of compound, at a known concentration, is added to a known volume of another compound to determine the concentration of the latter, the process is referred to as
A titration
Using the letters on the image, identify each component of the Bunsen burner.
A. barrel B. air inlet C. gas inlet D. gas regulator
Determine where each type of cleaning solution should be discarded after use.
Acid solution used to clean a crucible- waste container Solvent used to rinse chemicals out of a beaker- waste container Water used to rinse detergent out of a flask- sink
Determine what type of reaction each unbalanced chemical equation represents.
AgNO3+NaCl⟶NaNO3+AgCl Double replacement CaCl2+Na3PO4⟶Ca3(PO4)2+NaCl Double replacement NaHCO3⟶CO2+NaOH Decomposition Mg+H2SO4⟶MgSO4+H2 Single replacement
What are the best practices for safely handling waste in the lab?
Always wear appropriate Personal Protective Equipment. Check labels or instructions before any disposal.
Which statements are true concerning a substance with a high specific heat?
An example substance is water. The substance cools down slowly after heating.
The indicator phenolphthalein is added to the
Analyte
When is the best time to clean glassware during the lab session?
As soon as practical after use
What parts are present in every chemical equation?
At least one reactant At least one product An arrow
Determine when to put on disposable gloves for work in the lab.
Before handling any glassware or chemicals for the experiment
When should lab participants look at the Safety Data Sheet (SDS) of a substance?
Before using the substance
Which compounds could be represented by the empirical formula CH2CHX2 ?
C3H6 C2H4 C8H16
Determine each type of reaction.
CO(g)+2H2(g)⟶CH3OH(l) Combination 2Fe(s)+6HCl(aq)⟶2FeCl3(aq)+3H2(g) Single replacement CaCl2(aq)+Na2CO3(aq)⟶2NaCl(aq)+CaCO3(s) Double replacement NH4NO3(s)⟶N2O(g)+2H2O(l) Decomposition 2C2H2(g)+5O2(g)⟶4CO2(g)+2H2O(l) Combustion
For each reaction, determine whether it is an example of combustion or not.
CO2+4H2⟶CH4+2H2O - not combustion 2C2H6+7O2⟶4CO2+6H2O - combustion C+O2⟶CO2 - combustion 2NO+O2⟶2NO2 - combustion 2N2O5⟶4NO2+O2- not combustion
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.
What color is phenolphthalein when the solution is acidic?
Colorless
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
the equation to calculate density is ___ where D is the density, m is the ___ and V is the ___
D=m/V, mass, volume
What occurs in endothermic reactions?
Heat energy is absorbed.
When exothermic reactions occur
Heat energy is released
Which procedure cannot be performed on a hot plate, requiring a Bunsen burner instead?
Heating a crucible to remove water from a hydrate
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
Suppose 0.0350 g Mg0.0350 g is reacted with 10.00 mL of 6 M HCl to produce aqueous magnesium chloride and hydrogen gas. Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g) What is the limiting reactant in this reaction?
Magnesium metal
Identify the color flame each element that produces in a flame test.
Na-brilliant yellow flame K-fleeting lavender flame
Hydrochloric acid and sodium hydroxide react to form
NaCl(aq) + H2O(l)
Determine whether or not each chemical formula is an empirical formula.
NaMnO4-emp CaCO3-emp C6H12O6-not emp K2C2O4-not emp Ba3(PO4)2-emp
The reaction between sodium hydroxide and hydrochloric acid is considered which type?
Neutralization
Refer to the periodic table to find the correct molar mass for each element and compound.
O=15.999 g/mol O2=31.998 g/mol C2H6=30.067 g/mol S=32.059 g/mol Cl=35.446 g/mol CH4=16.042 g/mol
What is generally the best approach when liquid from a large reagent bottle is needed in an experiment?
Pour some of the reagent from the bottle into a beaker, then use as needed in the procedure.
Identify the common indicators that a chemical reaction has occurred.
Precipitate being formed Bubbles being produced A color change A change in temperature
What should you do every time before you leave the lab?
Remove your gloves. Wash your hands. Remove your lab coat, if you are wearing one.
How should spill cleaning materials be discarded?
Seal in a labeled plastic bag, then place in the solid waste container.
Which term describes a solution having a very well-known concentration of solute?
Standard solution
When equal moles of an acid and a base are mixed, after reaction the two are compounds are said to be at the
Stoichiometric point
What is the general definition of heat capacity?
The change in heat required to change the temperature of something by one degree Celsius
Under what conditions should a student inform the instructor of a lab injury?
The instructor must be informed of all laboratory injuries.
A sample of gas is subject to changes in conditions. Predict the effect of each change.
The pressure and the temperature are both decreased by 50%. What will happen to the volume? - stay The volume and temperature remain constant, while some of the gas is let out of the container. What will happen to the pressure?- decrease The pressure and volume are increased. What will happen to the temperature? - increase The pressure is kept constant, while the temperature is decreased. What will happen to the volume? - decrease
In the Ideal Gas Law lab, how is the temperature of the hydrogen gas determined?
The temperature of the water bath is measured after the reaction, which is assumed to be the same temperature as the gas.
The liquid dispensed from a burette is called
Titrant
What is the purpose of stirring a solution while it is being heated?
To help evenly distribute heat throughout the solution
What should you do if your Bunsen burner does not light after a few tries with the striker?
Turn off the gas cock for 10 seconds before trying again.
Which has a greater energy, long wavelength red light or short wavelength UV light?
UV light
What is the main precaution to take if a Gas Cylinder sign is present in the lab?
Visually check that the gas cylinder is restrained but keep a safe distance from it.
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
What is the equivalence point of a titration?
When the amount of acid and base are equal
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
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-True Chewing gum is okay in the lab as long as you don't blow bubbles- False Tobacco products of all kinds are prohibited in lab- True Beverages are allowed in lab as long as they are in containers with lids- False
Determine the relative order of the metric prefixes of kilo-, micro-, centi-, and milli-.
For the same base unit, micro- is less than milli-, which is less than centi-, which is less than kilo-.
In the reaction of magnesium metal with hydrochloric acid, how do you determine when the magnesium metal has reacted completely?
Gas bubbles are no longer produced. The magnesium metal is gone.
Identify the step that is not recommended when responding to an emergency.
Gather your belongings.
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- Gloves While checking on a stirring solution, the solution splashes up towards your face- Goggles While transferring a solution from a flask to a beaker, the solution accidentally spills down the front of the lab bench- Lab coat While pulling an empty beaker off the shelf at the beginning of lab, it slips out of your hand onto the floor-Closed-toe shoes
how can you improve your ability to see the indicator color change at the endpoint of a titration?
add a large amount of indicator at the beginning of the titration
solution of an unknown concentration that has another solution slowly added to it
analyte
Identify the types of information that are necessary to communicate with emergency responders.
any chemicals involved in an incident any other hazards present in the lab how the incident happened
Determine whether each of the examples represents a colligative property or a non-colligative property.
boiling point elevation-colligative color-non colligative freezing point depression - colligative vapor pressure lowering - colligative density- non colligative
glassware that allows a solution to be precisely and slowly added to another solution
burette
When an alarm sounds in the laboratory, it is important to respond ____and remain ___Listen for any other instructions, turn off any ____ in use, and be prepared to leave immediately.
calmly, quiet, equipment
determine whether the stopcock should be completely open, partially open, or completely closed for each activity involved with titration
close to the calculated equivalence point - partially open conditioning the burette with titrant - completely closed filling the burette with titrant - completely closed at the beginning of a titration - completely open
Suppose you are given the mass of each element in a compound sample. To calculate the empirical formula, start 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.
Identify the safety equipment designed to deal with each emergency listed.
cuts or minor burns- first aid kit large fire on the bench top-fire extinguisher fire on a person- fire blanket chemicals on clothes- safety shower chemicals in eyes- eyewash station
In general, which characteristics are necessary for a location to be suitable for chemical storage?
dark, dry, cool
consider the trendline on a graph of Mass vs. Volume of a solid or liquid. What information can be obtained about the substance from the slope of this line?
density
a hydrometer is a tool used to measure the ___ of a liquid relative to that of ___
density, water
When cleaning a buret, begin by coating the inside with ___ Empty most of it out, then drain the rest by ___ Rinse with ___ then hang upside-down on a buret rack.
detergent solution opening the stopcock deionized water
Multiple spectra and colors are observed in the atomic spectra lab. What kind of electronic transitions are responsible for colored light being given off?
emission
when the required amount of one solution has been added to the second solution to complete the reaction
equivalence point
Choose the most appropriate task for each pictured glassware
flask (cone shaped) - containing a stirred reaction mixture beaker ( wide cylinder shape) - pouring an approximate volume of liquid into a buret graduated cylinder (narrow cylinder) - measureing out a volume of a liquid
Determine the best way to deal with each of the following items that may dangle into the way during lab work.
flowy sleeves- tie back or secure loose bracelets-remove long necklaces- remove long hair - tie back or secure long earrings- remove
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
Determine which items of personal protective equipment (PPE) you will likely use in a general chemistry lab.
gloves, lab coat, goggles
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
Which types of signs are posted to convey information about chemical storage?
hazard signs such as "flammable", "oxidizer", and "corrosive" NFPA diamond gas cylinder sign
A calorimeter measures the ___ involved in reactions or other processes by measuring the ___of the materials ___ the process. The calorimeter is ___ to prevent transfer of heat to outside the device.
heat, temperature change, surrounding, insulted
Most chemicals can be cleaned up with a general spill kit, but a few chemicals require specialized spill procedures. For each substance listed, determine whether a general spill kit is sufficient or if a specialized spill kit is needed.
hydrofluoric acid - special mercury-special phosphoric acid-general acetone-general methanol-general
What information is necessary to review in order to be considered familiar with the Safety Data Sheet (SDS) of a substance?
identification and description of substance Hazard warnings Personal protection and first aid recommedations Handling, storage, and reactivity information
for each described liquid , determine the behavior of a hydrometer calibrated around the density of pure water
in a liquid that is more dense than water - float higher than position in pure water in a liquid that us less dense than pure water - float lower than position in pure water in a liquid with the same density as water - float in the same position as pure water
A balloon is inflated outside on a cool morning. As the temperature rises, reaching its peak in the afternoon, the volume of the balloon will ___ . As the temperature cools down again in the evening, the volume of the balloon will ___
increase, decrease
a reagent added to the analyte solution that changes color when the reaction is complete
indicator
What should you do every time you are about to heat glassware on a hot plate? Select one or more:
inspect the hot plate for frayed cords Check that there are no cracks in the glassware Ensure that the glassware is designed for heating
What the relationship between frequency and wavelength of electromagnetic radiation
inverse
The relationship between pressure and volume of a gas is ___ so that as volume decreases, pressure ___
inverse, increases
At the freezing point, the liquid form of a substance ___ the solid form of the substance.
is in equilibrium with
when a vinegar and oil salad dressing separates into two layers, the oil floats on top of the vinegar. the density of the oil ___ the density of the vinegar
is less than
If you double the wavelength of light, what happens to the energy of the photons?
it will decrease by one-half
Identify the equipment best suited for extinguishing each type of fire.
large fire on floor-fire extinguisher small benchtop fire-overturned beaker clothing fire- fire blanket
Between flame tests, the nichrome wire is cleaned. What color should appear when a properly cleaned nichrome wire is introduced into the flame?
light or faint yellow
Magnesium reacts with oxygen in the air when ___ Unlike other reactions, you should not ___ this reaction.
lit with a Bunsen burner look directly at
The freezing point of a 1 m solution of FeCl3 is expected to be ___ that of a 1 m solution of glucose. This is because FeCl3 ___ and ___ compared with glucose.
lower than, is an electrolyte, has a larger van't Hoff factor
what practice will NOT help you make an accurate volume reading on a burette at the beginning of a titration ?
make sure that the meniscus starts at exactly 0.00 mL
Consider the Bohr model of the atom. Which transition would correspond to the highest frequency of light emitted?
n=4 to n=1
To isolate a single variable when rearranging equations, move all other variables to the ___ of the equation by using ___ on them and remembering to perform that operation ___ Make sure the rearrangement has the target variable ___
other side the opposite function on both sides of the equation in the numerator, not the denominator
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
One calorie (cal) is the amount of heat needed to ___ the temperature of one gram of water one degree Celsius.
raise
identify the description that applies to the substance represented by each NFPA diamond
red=0,blue=3,yellow=0,white=OX - oxidizer, not flammable red=0,blue=3,yellow=2,white=... - moderately unstable or reactive red=3,blue=2,yellow=0,white=... - stable, has health risks but no special hazards red=4,blue=2,yellow-0, white=..., - has a flash point below room temperature
In the context of a balanced chemical equation, a subscript is a number to the lower right of an element or ion within formula and it applies to only the part of the formula it follows. A coefficient is a number to the left of a formula and it applies to the entire formula it precedes. Only coefficients should be added or changed when balancing chemical equations.
subscript only the part of the formula it follows. coefficient entire formula it precedes. coefficients
Mass is conserved in an experiment if the___ of the individual component masses equals the mass of the____
sum mixture of the components
before running a titration , you calculate the expected endpoint. However, when performing the experiment, you pass the expected endpoint with no visible color change. what is most likely the problem with the titration set up?
there is not enough indicator in the analyte
solution of known concentration that is slowly added to a solution of unknown concentrate
titrant
Determine where to dispose of each type of waste.
titrant solution- bottle with cap unused solid reagent- solid waste container broken flask- lined with puncture resistant bag syringe tips- container
process of slowly adding a solution to react with another solution and determine the concentration of one of the solutions based on the reaction between them
titration
Suppose an air bubble is trapped in the eudiometer before starting the experiment. After the experiment is finished, the resulting value of R would be
too large
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 ___ of the meniscus aligns with the desired volume marking when you look at the graduated cylinder from ___
top, bottom, eye level
Identify what each GHS symbol signifies about the type of chemical present in a bottle or storage cabinet.
two liquids being poured- corrosive, chemical flame-flammable chemical circle on fire-oxidizing chemical
Visible light falls into wavelength ranges of 400-700 nm, for which 1 m=1×109 nm1 m=1×109 nm. The energy and wavelength of light are related by the equation E=hc/λwhere E is energy in Joules, h is Planck's constant (6.626×10−34 J-s6.626×10−34 J-s ), c is the speed of light ( 2.998×108 m/s2.998×108 m/s ), and λ is the wavelength in m. If a visible light photon has a wavelength of 669.8 nm, what is the energy of the photon (in J)?
2.966e-19 Convert the wavelength from nanometers to meters using the relationship that 1 m=1×109 nm. λ in m=669.8 nm×(1 m/1×109 nm) Then substitute the wavelength into the equation. E=hc/λ=(6.626×10−34 J-s)(2.998×108 m/s)/ λ in m
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 2.39mL. after running the titration and reaching the endpoint, you read the base titrant volume as 23.73mL. What volume in mL of base was required for the titration?
21.34
If 0.98 g of an unknown was dissolved in 10.30 g of solvent and the resulting solution has a molality of 0.45 m, what is the molar mass of the unknown?
211 g/mol mol solute =molality × kg solvent =0.45 m ×0.0130 kg =0.004563 mol solute molar mass =0.98 g0.004653 mol =211 g/mol
The temperature of a room is 20.5 °C. What is this temperature expressed in Kelvin (K)?
293.7 20.5∘C+273.15
What is the correct reading of the temperature in the pictured thermometer? Make sure to report your reading with the appropriate significant figures.
35.9 °C
choose the best graduated cylinder to make each measurement in a single use
36 mL of water - a 50 ml with markings every 10 mL 18.5 mL of a NaCl solution- 25 mL with markings every 1mL 5.75 mL of a sucrose solution - 10 mL with markings every .1 mL
What is the correct reading of the volume in the pictured buret?
39.95 mL
suppose you are measuring the mass of a solid sample on a balance using a weigh boat. you record the data in a table: mass of weigh boat: 1.062 g mass of weigh boat and sample: 5.934 what is the mass of the solid sample in g?
4.872 g mass of weigh boat and sample - mass of weigh boat = mass of sample
Suppose you mix 100.0 g of water at 27.7 oC with 75.0 g of water at 76.8 oC. What will be the final temperature of the mixed water, in oC?
48.74 q=mcΔT
identify which balance was used to make each mass reading
6.539 g - a balance with +- 0.001g tolerance 0.90g - a balance with +- 0.01g tolerance 1.230g - a balance with +- 0.001g tolerance 5.43g - a balance with +- 0.01g tolerance 4.0000g - a balance with 0.0001g tolerance
The H2 produced in a chemical reaction is collected through water in a eudiometer. If the pressure in the eudiometer is 760.0 torr and the vapor pressure of water under the experimental conditions is 19.7 torr, what is the pressure (torr) of the H2 gas?
740.3 Ptotal−PH2O=PH2
Identify correctly formatted scientific notation.
8×1068×106 4.532×10−9 6.1×1012
Knowing that one day is 24 hours and one hour is 60 minutes, how many minutes are in 6.7 days? Type answer:
9648
Using the letters on the image, identify each component of the liquid waste set-up.
A Funnel B container C label D container
Determine whether each described process is endothermic or exothermic.
Wood burns in a fireplace - exo A process with a calculated negative q - exo Solid dissolves into solution, making ice pack feel cold - endo A process with a calculated positive q - endo Ice melts into liquid water - endo Acid and base are mixed, making test tube feel hot - exo
Which is NOT a good source of information about the hazards that affect waste disposal in a chemistry lab?
Your lab partner
Predict the products of hydrochloric acid reacting with zinc metal.
ZnCl2 H2
What appearance of an acidic analyte solution containing phenolphthalein indicates the endpoint of titration with a basic solution?
a persistent pale pink color throughout the solution
Suppose you mix two solutions in a test tube and the test tube becomes hot. This is
a sign of a chemical reaction chemical changes can release heat.
To convert between units, you need to know the relationship between units. For example, one mile equals 5280 feet. This relationship can now be used as a conversion factor, set up as required by the question. For each conversion, choose the correct arrangement of the conversion factor and complete the calculation. 1. Convert 7860 feet to miles 7860 feet×( A )( B )7860 feet× ( A )( B )
a= 1 mile b=5280ft
