Chem1101L: Final Exam (Quizzes)
What is the value of the gas constant R
0.0821 L*atm/mol*K
Calculate the moles of ammonia present in 4.462 g sample of ammonia, which has a molar mass of 17.030 g/mol
0.2620 moles moles of substance=mass in g x (1 mole of substance/molar mass) 4.462 g NH3 x (1 mol/17.030 g/mol)
Consider the reaction of propane with oxygen. C3H8+5O2⟶3CO2+4H2O How many moles of CO2CO2 molecules are produced when 1.7 moles of O2 molecules react completely?
1 1.7 M O2 x (3 M CO2/5 M O2)
In case of accidental contact with chemicals, how long should the eyes be flushed at the eyewash station?
15 minutes
A+B⟶C If you react 3 moles of reactant A with 1 moles of reactant B, what will be present after the reaction?
2 moles of reactant A and 1 mole of product C
Acid vs. base
Acid donates H Base accepts H
Endothermic and Exothermic
An endothermic reaction takes in heat from the surroundings and feels cold from the outside. Heat is a reactant because it is being added. An exothermic reaction gives off heat to its surrounding and feels hot from the outside. Head is a product because it is being lost
When using a pH meter to monitor a stirring reaction mixture, where should you place the pH sensor electrode?
Between the storing vortex and the side of the glassware
What is true about a chemical reaction at equilibrium?
The forward reaction rate is equal to the reverse reaction rate
Which reaction is occurring in the test tube? (White film in clear liquid)
The image shows a precipitation, in which a solid product is formed from two reactant solutions (aq)+(aq)--> (s)+(aq)
volume of a cylinder
V=πr²h
How do you know when the moles of acid equal the moles of the base in a titration of an acid with the base?
When the indicator changes at the endpoint of the titration
When acid is added to pure water, the pH ___, and when the base is added to pure water, the pH ___
decreases increases
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 bare finger
NFPA diamond blue red yellow white
health hazard fire hazard reactivity specific hazard
Which of the following would NOT be helpful in the separation of a mixture of sand and salt?
magnet
Most of the ___ people encounter in every day life consists of ___ of different substances
matter mixtures
___ are combinations of two or more substances
mixtures
Polar vs. Nonpolar solubility
polar molecules are more likely to dissolve in polar solvents like water than nonpolar solvents like oil nonpolar molecules are more likely to dissolve in nonpolar solvents like oil than polar solvents like water polar to polar nonpolar to nonpolar
Identify the observations that indicate an added substance is insoluble in water
the combination of the substance and water appears cloudy after mixing and allowing it to settle a clear line appears between the added liquid and water after mixing and allowing it to settle the added solid settles to the bottom after mixing allowing it to settle
What is the last step of any spill cleanup procedure?
wipe down the affected area with detergent and water
Which is NOT a good source of information about the hazards that affect waste disposal in a chemistry lab?
your lab partner
According to solubility rules, which compound should dissolve in water? CaSO4 MgCO3 K3PO4 AgBr
CaSO4
Temperature from Celsius to Kelvin
Celcius + 273.15
Suppose you mix an unknown solid with oil and the added solid dissolves into the oil. What is most likely true about the unknown solid?
It is a non polar solid.
Nonpolar vs. polar with geometry
Linear and Tetrahedral are non polar because of the overall symmetry. Non polar molecules do not have a net difference in electronegativity, and it is the most symmetrical Polar molecules have bonds with significant difference in electronegativity, arranged in a way that they do not counteract with each other.
According to the solubility rules, which compound should not dissolve in water? (NAGSAG) MgSO4 Na2CO3 Ca(NO3)2 MgCO3
MgCO3
When taking pH measurements of solutions, why is it important to stir thoroughly after adding each reagent?
Mixing helps ensure that the measured pH is reflective of the entire solution
Molarity formula
Molarity=moles of solute/liters of solution
While setting up a beaker to boil a solution on a hot plate, you notice that the stirring is erratic and unstable. What should you do to stabilize the stirring solution?
Move the beaker to the center of the hot plate Turn down the stirring speed
Suppose you mix solutions according to the given equation. Na2SO4(aq)+2KCl(aq)⟶2NaCl(aq)+K2SO4(aq)--> Na2SO4(aq)+2KCl(aq)⟶2NaCl(aq)+K2SO4(aq) What evidence of a reaction do you expect to see?
No reaction should occur
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 21.4 torr, what is the pressure (torr) of the H2 gas?
P(total)=P(H2O)+P(H2) 760.0 torr-21.4 torr
Suppose you are collecting gas over water at 23 C and obtain a pressure reading of 781.4 mm Hg. If the vapor pressure of water is 21.1 mm Hg at the collection temperature, what is the pressure of the collected gas?
P(total)=P(gas)+P(water) P(gas)=P(total)-P(water) 781.4 mmHg-21.mmHg
Ideal gas law equation
PV=nRT pressure volume moles gast constant temperature
What is the first step for response to an emergency situation?
Remain calm and quiet, gather information, and assess the situation
When performing quantitative tests to study ions, such as chloride, in solution, why should you use deionized or distilled water rather than tap water?
Tap water might contain ions that interfere with the tests
Under what conditions should s student inform the instructor of a lab injury?
The instructor must be informed of all laboratory injuries
What statements are always true about limiting reactants?
The limiting reactant is completely used up in the reaction There will be an excess of other reactants at the end of the reaction The limiting reactant dictates the amount of product
Which process is used to separate soluble compounds from insoluble compounds?
Extraction
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 the set of measurements
accuracy precision
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
A neutralization reaction is a reaction between ___ that results in the formation of ___ and a ___
an acid and a base water salt
Identify the types of information that are necessary to communicate with emergency
any chemicals involved in an incident any other hazards present in the lab how the incident happened
How should students prepare to use chemicals in the lab?
become familiar with the chemicals to be used, including exposure or spill hazards locate the spill kits and understand how they are used
Determine when to put on disposable gloves for work in the lab
before handling any glassware or chemicals for the experiment
Two single bonds and two lone pairs of electrons Three single bonds and one lone pair of electrons Two double bonds and no lone pairs of electrons Four single bonds and no lone pairs of electorns
bent trigonal pyramidal linear tetrahedral
What visible sign does NOT indicate a precipitation reaction when two solutions are mixed?
bubbling in the test tube
Determine whether each observation generally corresponds to a physical change or a chemical change The color of a substance changes over time A precipitate is formed from two solutions A solid dissolves into water Bubbles are produced upon mixing two solutions A solution heats up upon mixing with another A liquid freezes into a solid
chemical chemical physical chemical chemical physical
Mixtures are characterized by two fundamental properties: Each of the substances in the mixture retains its ___ property Mixtures are separable into these components by ___ means
chemical physical
Determine whether each property is a physical or chemical property: flammability color melting point solubility density reactivity
chemical physical physical physical physical chemical
What are the substances making up a mixture called?
components
In general, which characteristics are necessary for a location to be suitable for chemical storage?
dark cool dry
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
When the required amount of one solution has been added to the second solution to complete the reaction Glassware that allows a solution to be precisely and slowly added to another solution Process of slowly added a solution to react with another solution and determine the concentration of one of the solutions based on the reaction between them A reagent added to the analyte solution that changes color when the reaction is complete Solution of an unknown concentration that has another solution slowly added to it Solution of known concentration that is slowly added to a solution of unknown concentration
endpoint buret titration indicator analyte titrant
How do you determine the last digit in any measured number on a nondigital instrument?
estimate one digit past the smallest precisely known digit or marking
How can solid dissolved in water be separated from the water?
evaporation
When studying the tetrachlorocobaltate (II) ion equilibrium in alcohol, there is a warning that all glassware must be dry when preparing the equilibrium solution. Why is this warning included?
excess water will act as added reactant and cause the equilibrium to proceed more toward the products
This process if separating a solid from a liquid by means of a porous material
filtration
A solid is caught on paper or a membrane while the liquid passes through A solvent is added to dissolve only one mixture component and then the liquids are separated A solid mixture is heated. One component transitions directly between solid and gas. A liquid is carefully poured our, leaving the solid behind in the container
filtration extraction sublimation decantation
Identify the step that is NOT recommended when responding to an emergency
gather your belongings
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
Solution with greater solute concentration than the solution in the cell Solution that involves no net movement of water with the cell Solution that causes water to move into the cell Solution that causes water to move out of the cell Solution with lower solute concentration than the solution in the cell Solution with equal solute concentration to the solution in the cell
hypertonic isotonic hypotonic hypertonic hypotonic isotonic
What are minor components in a mixture called?
impurities
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
The relationship between pressure and volume of a gas is ___ so that as volume decreases, pressure ___
inverse increases
Determine which items of personal protective equipment (PPE) you will likely use in a general chemistry lab
lab coat gloves goggles
Match each lab incident to the item of PPE that will protect you from it: 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 While picking up a buret, an unknown solution left by a previous solution drips onto your hand
lab coat goggles closed toe shoes gloves
Magnesium reacts with oxygen in the air when ___. Unlike other reactions, you should not ___ this reaction.
lit with a Bunsen burner look directly at
Choose the most appropriate task for each piece of glassware: graduated cylinder Erlenmeyer flask beaker
measuring out a volume of liquid containing a stirred reaction mixture pouring an approximate volume of liquid into a buret
solid to liquid gas to solid gas to liquid liquid to solid liquid to gas solid to gas
melting deposition condensation freezing vaporization sublimation
Suppose you mix a solid into water and not all of it dissolves. This is ___ because ___
not a sign of a chemical reaction the undissolved solid is not a new substance
Identify the equipment best suited for extinguishing each type of fire: small bench top fire large fire on floor clothing fire
overturned beaker fire extinguisher fire blanket
Oxidation and reduction
oxidation is the loss of electrons, while reduction is the grain of electrons
In the reaction Mg + 2HCl → MgCl2 + H2 Mg is ___ H is ___
oxidized reduced
Buffer capacity is the amounftof acid or base a buffer can handle before pushing the ___ outside of the buffer range
pH
pH formula
pH=pKa+log([A]/[HA]) where HA is the acid and A is the conjugate base
The comparison of the experimental amount of product to the calculated amount The calculated amount of product under ideal conditions The amount of product experimentally produced
percent yield theoretical yield actual yield
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
Identify the common indicators that a chemical reaction has occurred
precipitate being formed a color change a change in temperature bubbles being produced
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 loose bracelets long necklaces long earrings long hair flowy sleeves
remove remove remove tie back or secure tie back or secure
What should you do every time before you leave the lab?
remove your lab coat, if you are wearing one wash your hands remove your gloves
Which signs are typically posted in areas of active lab work?
safety equipment signs sign prohibiting food and drink personal protective equipment (PPE) sign chemical storage signs
In the Insoluble and Soluble lab, the dropper bottles containing the anions to be studied were all ___ salt solutions. The dropper bottles containing the cations to be studied were all ___ salt solutions.
sodium nitrate
Sublimation is a phase change from ___ to ___. The ___ phase is not present in this change
solid gas liquid
What visible signs indicate a precipitation reaction when two solutions are mixed?
solid settling out in the test tube a hazy or cloudy appearance
Determine where to dispose of each type of waste: unused solid reagent titrant solution syringe tips broken flask
solid waste container Nalgene bottle with cap sharps container box lined with puncture resistant bag
Identify each category of substance as soluble or insoluble in water most nitrate salts most silver salts salts of group 1 most carbonate and phosphate salts most halide (Br, Cl, and I) salts
soluble insoluble soluble insoluble soluble
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
When taking a measurement of a pH meter, keep the instrument in the ___ until it is needed. Rinse the pH meter with ___ and gently pat dry. Place the meter in the sample solution, and record the measurement when the pH ___
storage solution deionized water stabilizes
Dalton's Law of Partial Pressures states that the total pressure of a gas mixture is equal to the ___ of the ___ as long as ___
sum partial pressures of all the component gases the gases do not react with each other P(total)=P1+P2
According to La Chatelier's Principle, heat is applied to an exothermic reaction towards ___. Heat applied to an endothermic reaction will shit the reactions towards ___.
the reactants the products
T/F Food items should not be brought into the lab Tobacco products of all kinds are prohibited in lab Beverages are allowed in lab as long as they are in containers with lids Chewing gum is okay in the lab as long as you don't blow bubbles
true true false false
The composition of homogeneous mixtures is ___
uniform
Determine whether each of the properties describes applies to volumetric or graduates 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
Identify the pieces of glassware that are most effective for accurate solution preparation
volumetric flask volumetric pipet
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 while 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
At what times should a pH electrode be submerged in a solution?
when not being used between measurements when monitoring a reaction in a beaker when being stored in a storage cabinet
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
percent change in mass
% change= (final size-original size/ original size) x100
Percent composition
% composition=(mass of mixture components/total mass of mixture) x100
Equilibrium constant
([C]^d[D]^d)/([A]^a[B]^b) where aA+bB <--> cC+dD and pure solids and liquids are not included
In a precipitation reaction, what symbol identifies the precipitate product?
(s)
Oxidation of MnO2
+4 Mn+O2=0 Mn+(-2)2=0 Mn+(-4)=0 Mn=+4
What information does not need to be included on a chemical waste label?
a description of the experiment the chemicals were used for
Percent yield
actual yield in g/theoretical yield in g
Determine the number of sig figs in each measurement. Then, choose the representation of the number where x is in place of the estimated digit from the measurement: 14.8 10.25 0.05 1.000 6200 403
3- 14.x 4- 10.2x 1- 0.0x 4- 1.00x 2- 6x00 3- 40x
A formic acid buffer solution contains 0.20 M HCOOH and 0.21 M HCOO. The pKa of formic acid is 3.75. What is the pH of the buffer?
3.77 pH=3.75+log(0.21/0.20)
What is the mass of NaCl in 50.2 mL of a 10.0% w/v solution?
5.02 (10.0/100.0)x50.2
What is the weight per volume of 50.0 mL NaCl solution that contains 3.75 g NaCl?
7.5% %(w/v)= (mass of solute/ volume of solution)x100 (3.75/50.0)x100
A buffer solution must contain
a relatively high amount of both a weak acid and its conjugate base dissolved in water
Suppose you mix two solutions in a test tube and the test tube becomes hot. This is ___ because ___
a sign of a chemical reaction chemical changes can release heat