Chem 121 Lab Final
In a precipitation reaction, what symbol identifies the precipitate product?
(s)
Oxidation state of Cu in Cu(OH)2
+2, Copper (II) Hydroxide
Oxidation state of Cu in Cu(NO3)2
+2, Copper (II) Nitrate
Oxidation state of Cu in CuSO4
+2, Copper (II) Sulfate
If you require 29.16 mL of 0.561 M NaOHNaOH solution to titrate 188.6 mL of H2SO4 solution, what is the concentration of the H2SO4 solution?
.0434
Calculate the moles of ammonia present in a 9.412 g sample if the molar mass of ammonia is 17.030 g/mol.
.5527 mol
If you require 32.98 mL of 0.1776 M NaOH solution to titrate 10.0 mL of HC2H3O2 solution, what is the molar concentration of acetic acid in the vinegar?
.586
Oxidation state of Cu in Cu metal
0
Determine whether each of the properties described applies to volumetric or graduated glassware: 1) Used for applications in which great accuracy is needed 2) Capable of measuring a range of volumes of liquid 3) Designed to measure one specific volume of liquid
1) Volumetric, 2) Graduated, 3) Volumetric Volumetric: Used for applications in which great accuracy is needed, used to accurately measure and dispense one specific volume of liquid Graduated: Used to measure and dispense a range of volumes of liquid, but with less accuracy
Identify which balance was used to make each mass reading: 1) .90 g 2) 1.230 g 3) 6.539 g 4) 5.43 g 5) 4.0000 g a) A balance with ±0.001 g tolerance b) A balance with ±0.01 g tolerance c) A balance with ±0.0001 g tolerance
1) b, 2) a, 3) a, 4) b, 5) c
Choose the best graduated cylinder to make each measurement in a single use: 1) 5.75 mL of a sucrose solution 2) 18.5 mL of a NaCl solution 3) 36 mL of water a) A 25 mL graduated cylinder with markings every 1 mL b)A 50 mL graduated cylinder with markings every 10 mL c)A 10 mL graduated cylinder with markings every 0.1 mL
1) c, 2) a, 3) b
Put the #'s in correct order: When filling a buret for a titration, first adjust the buret in the clamp so that ________. Then, _________ to add the titrant into the buret. The titrant should be filled __________. 1)the opening is near eye level 2)use a funnel 3)almost to the zero mark
1,2,3
Consider the balanced reaction of magnesium and oxygen. 2Mg+O2⟶2MgO2Mg+OX2⟶2MgO What mass, in grams, of MgO can be produced from 1.02 g of Mg and 2.15 g of O2?
1.69 g
Barium can be analyzed by precipitating it as BaSO4 and determining the mass of the precipitate. When a 0.269-g sample of a barium compound was treated with excess H2SO4, 0.0891 g of BaSO4 formed. What percentage of barium is in the compound?
19.5%
How many significant figures are in the number 2.1?
2
What is the subscript on the anion in the neutral formula in Strontium Phosphide?
2
Which reaction forms a precipitate? 1)Mg(s)+HCl(aq)⟶MgCl2(aq)+H2(g) 2)KCl(aq)+AgNO3(aq)⟶AgCl(s)+KNO3(aq) 3)C(s)+O2(g)⟶CO2(g) 4)HBr(aq)+LiOH(aq)⟶LiBr(aq)+H2O(l)
2)KCl(aq)+AgNO3(aq)⟶AgCl(s)+KNO3(aq) It is the only reaction that forms a solid (precipitate).
Oxidation state of Cu in CuO
2, Copper (II) Oxide
Put the #'s in correct order: In the reactionMg + 2HCl → MgCl2 + H2Mg is __________ and H is ___________. 1) reduced 2) oxidized
2,1
Put the #'s in correct order When preparing for work in the fume hood, be sure to gather all necessary tools, glassware, and chemicals _________ to minimize the number of times the hood sash is raised and lowered. Work as much as possible in the ___________ of the work surface to keep the area tidy and promote air flow. If you need to step away from the experiment to obtain another item, ___________ the sash during this time. 1) middle 2) in advance 3) lower
2,1,3
Put the #'s in correct order: In order to use a pipet, place a __________ at the top of the pipet. Use this object to fill the pipet such that the __________ of the liquid is even with the volume line. Release the liquid, touching the tip of the pipet to the side of the container if necessary to release the last drop __________ the pipet tip. 1) Outside 2) Bulb or pump 3) Meniscus
2,3,1
Put the #s in correct order: When using the Tare function on a balance, start by ______________ Then, ________________ to cancel out that mass. Finally, ______________ and record the mass of your sample. 1)Add your sample to the glassware 2)Placing the glassware on the balance. 3)Pressing the Tare/Zero button.
2,3,1
What volume (in mL) of 3.0 M H2SO do you need to completely react with 0.64 g Cu(OH)?
2.2 mL
Find the average mass of product: 1)2.73g 2)2.00g 3)1.97g 4)1.47g 5)2.98g 6)2.28g
2.235g
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 2.29 mL. After running the titration and reaching the endpoint, you read the base titrant volume as 26.15 mL. What volume, in mL, of base was required for the titration?
23.86 mL
What is the subscript on the cation in the neutral formula in Strontium Phosphide?
3
Put the #'s in correct order: To determine an ionic formula from a compound name, start by _________ for each element in the compound. Then, use the __________ to determine the subscripts necessary to __________. 1)charge of each ion 2)create a formula unit with no net charge. 3)finding the expected charge
3,1,2
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
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
Which compound name does not correspond to an ionic compound? 1)Silver iodide 2)Molybdenum(V) chloride 3)Magnesium bromide 4)Phosphorus pentafluoride
4)Phosphorus pentafluoride
Calculate the average density: 1)5.08 g/mL 2)4.92 g/mL 3)5.13 g/mL
5.04 g/mL
Calculate the mass percent of a vinegar solution with a total mass of 95.74 g that contains 3.63 g of acetic acid.
96.3%
Suppose you start with 0.486 g of Cu. After performing all the reactions, you have 0.470 g of Cu. What percentage of the copper did you recover?
96.7%
volatile
A characteristic that describes substances that evaporate readily, producing large amounts of vapors
synthesis reaction
A+B->AB
single-displacement reaction
AB+C-> AC+B
double-displacement reaction
AB+CD->AC+BD
decomposition reaction
AB->A+B
Aluminum selenide
Al2Se3
Solution of an unknown concentration that has another solution slowly added to it
Analyte
Barium sulfide
BaS
What are the best practices while sharing a lab balance with other students?
Brush off any chemical dust around the balance after each use. Alert your TA or instructor about any issues with the balance.
Glassware that allows a solution to be precisely and slowly added to another solution
Buret
Which compounds could be represented by the empirical formula CH2?
C2H4, C3H6, C8H16
CaCl2
Calcium chloride
CaO
Calcium oxide
Determine the type of equation: Ca2+(aq)+2Cl−(aq)+2Na+(aq)+CO32−(aq)⟶2Na+(aq)+2Cl−(aq)+CaCO3(s)
Complete net ionic equation
How should you prepare a buret for titration before loading it with titrant?
Condition the buret with titrant solution.
What should you do if you are using a balance that has persistent fluctuations in mass?
Contact your TA or instructor to adjust the balance.
CuCl2
Copper(II) chloride
Cu2O3
Copper(III) oxide
When using a clamp and ring stand to hold glassware and tools, what is the best position for the clamp?
Directly above the base of the ring stand
When you are done using most glassware in the lab, what should you do?
Dispose of any chemicals in the proper waste container. Return the glassware to the appropriate location to dry. Clean the glassware with a detergent solution.
When the required amount of one solution has been added to the second solution to complete the reaction
Endpoint
What is the best description of accuracy as applied to a set of measurements or data?
How well the average of a data set agrees with a known value
Identify effective techniques for accurate pipet use.
Identify effective techniques for accurate pipet use. Do not let liquid enter the pipet bulb or pump.
A reagent added to the analyte solution that changes color when the reaction is complete
Indicator
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.
What is the symbol for the element that forms the negative anion in Strontium Phosphide?
P
Identify the products for the reaction of lead(II) nitrate ( Pb(NO3)2(aq) and potassium iodide KI(aq).
PbI2(s) and KNO3(aq)
Identify the products for the reaction of lead(II) nitrate Pb(NO3)2(aq) and potassium iodide KI(aq).
PbI2(s) and KNO3(aq)
Identify the common indicators that a chemical reaction has occurred.
Precipitate being formed Bubbles being produced A color change A change in temperature
Identify techniques to be used for accurate solution preparation using a volumetric flask.
Read the liquid volume at eye level from the bottom of the meniscus. After the solvent is added, stopper and invert the flask to mix the solution.
What practice will not help you make an accurate volume reading on a buret at the beginning of a titration?
Read the volume at the bottom of the meniscus.
Ruthenium(IV) oxide
RuO2
What visible signs indicate a precipitation reaction when two solutions are mixed?
Solid settling out in the test tube. A hazy or cloudy appearance.
What is the symbol for the element that forms the positive cation in Strontium Phosphide?
Sr
SrBr2
Strontium Bromide
Two students preform a titration multiple times withe the averages being: Student A: 0.125 ± 0.008 M and Student B: 0.12 ± 0.03 M. Who has the more precise work, and why?
Student A because that student's data has a smaller standard deviation.
Identify the potential uses for an iron ring.
Suspending a funnel. Supporting a beaker on a piece of wire mesh. Holding a crucible placed in a clay triangle.
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
work surface
The horizontal, flat area of a fume hood upon which experiments are carried out
What statements are always true about limiting reactants?
The limiting reactant dictates the amount of product. The limiting reactant is completely used up in the reaction. There will be an excess of other reactants at the end of the reaction.
Titanium(IV) iodide
TiI4
Solution of known concentration that is slowly added to a solution of unknown concentration
Titrant
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
What is the purpose of stirring a solution while it is being heated?
To help evenly distribute heat throughout the solution.
ion
a charged version of an atom that is formed by losing or gaining electrons compared to the atom.
A macromolecule made of many repeated subunits, known as monomers.
a polymer
BaCl2
barium chloride
Cs2O
cesium oxide
ClO2
chlorine dioxide
CoI2
cobalt(II) iodide
Cu2O
copper (I) oxide
S2F10
disulfur decafluoride
soluble or insoluble? Most carbonate and phosphate salts
insoluble
soluble or insoluble? Most silver salts
insoluble
CaCl2(aq)+Na2CO3(aq)⟶2NaCl(aq)+CaCO3(s)
molecular equation
Determine the type of equation: Ca2+(aq)+CO32−(aq)⟶CaCOX3(s)
net ionic equation
Identify whether each change represents an oxidation or reduction. Then determine how many electrons were involved and which side of the reaction they should appear on in the half-reaction:
oxidation, 2, product
Identify whether each change represents an oxidation or reduction. Then determine how many electrons were involved and which side of the reaction they should appear on in the half-reaction: Al⟶Al3+
oxidation, 3, product
PBr5
phosphorus pentabromide
PBr3
phosphorus tribromide
Identify whether each change represents an oxidation or reduction. Then determine how many electrons were involved and which side of the reaction they should appear on in the half-reaction: Cu2+⟶Cu
reduction, 1, reactant
Rb2S
rubidium sulfide
soluble or insoluble? Most halide (Br-, Cl-, and I-) salts
soluble
soluble or insoluble? Most nitrate salts
soluble
soluble or insoluble? Salts of Group 1 elements
soluble
SF4
sulfur tetrafluoride
