CHEM Final Practice Questions

Which of the following is the final concentration of a solution if 2 mL of a 5 M solution is added to 5 mL of distilled water?

1.43 M

100 mL of 2.00 M HCl and 100 mL of 2.20 M NaOH were added to a styrofoam cup, and a 13.0 degrees celcius increase was observed from the resulting reaction. The mass of the solution was determined to be 213.4 g. What is the value of the calorimeter constant ( Cc ) for the styrofoam cup? Specific Heat of solution: 3.90 J g-1 K-1 Molar enthalpy of neutralization for NaCl: -58.3 kJ/mol Density of water: 1.00 g/mL

64.7 J/K

Which of the three components was isolated in the first step by filtration as residue?

AgCl and SiO2

Reactivity trends

increases down a group, decreases across a period

CO32- (carbonates)

insoluble

OH- (hydroxides)

insoluble

PO43- (phosphates)

insoluble

S2- (sulfides)

insoluble except Group 1A, 2A, and NH4+

The most reactive metal is the metal that always

loses electrons

Oxidation

loss of electrons

moles of NaOH

mLx 1L/1000mL, take ratio of both (NaOH and unknown)

In the lab, a student adds 15 drops of an unknown liquid into a watch glass. The student immerses both electrodes of a conductivity meter into the liquid and sees the LED on the meter brightly light up (both red and green light). Given the following unknowns, which is likely the identity of the unknown liquid.

1 M sodium chloride

Which of the following order is correct? 1. Metal reactivity Ca>Zn>Sn>Cu 2. Oxide stability CuO>ZnO>CaO 3. Metal reactivity Li>Na>K>Cs 4, Metal reactivity Mn>Fe>Ni>Cu

1 and 4 only

A group of students is doing the zinc titration experiment. They have transferred 25.12 mL of Zinc Chloride solution into the Erlenmeyer, added 2 mL buffer and 3 dropped of EBT. They then started titration and after 5.00 mL of EDTA is added, one student forget that they have added buffer and added another 2 mL of the buffer. The indicator changed from purple to blue at the end. How does 2 extra amounts of buffer affect the ZnxCly ratio?

x and y remains the same

enthalpy of reaction

∆H = q/mol

A 100.0 mL solution of 0.309 g of zinc chloride was prepared. Then 22.60 mL of the solution was titrated to the EBT end-point using 22.45 mL of 0.0300 M EDTA. What was the mass of chloride-based on your experimental data? Zn2+(aq) + EDTA4- (aq) -> [ZnEDTA]2- (aq)

0.0258 g

Predict the concentration of a solution with absorbance = 0.360

0.075 M

Calcium, barium, and magnesium are three elements in group 2 of the periodic table. Calcium is in period 4, barium is in period 6, and magnesium is in period 3. Choose the correct statements; 1. Calcium can replace barium in its solution 2. Both barium and calcium can replace magnesium in its solution 3. Calcium can oxidize magnesium in its solution 4. Only barium can replace calcium but magnesium can't replace calcium in it's solution 5. Magnesium can replace both calcium and barium in their solutions

2 and 4 are true

Na3PO4 + CoCl2 ------>

3 NaCl + CO3(PO4)2

An experiment was conducted using KNO3. The table below shows the data obtained after dissolving different masses of KNO3 in 10 mL of deionized water and then cooling to determine the temperature at which the different concentration of salts begin to recrystallize. If a student dissolves 24g of KNO3 in 120 mL of deionized, at what temperature do you expect to see recrystallization?

52.5 degree celcius

Double displacement reaction

AB + CD --> AD + CB

Does not react with metals

Au, Pt, Pd, Hg, Ag, Cu, Bi, Sb

The mole ratio study was conducted using the same procedure from experiment 7, and the data is provided for you below. Each of the 7 trials had a total volume of 60.0 mL... After considering the error, what is the actual identity of the acid?

Before HCl, After H2SO4

Arrange the following compounds according to increase solubility in water. I. Methanol II. Ethanol III. Pentanol IV. Decanol

IV< III < II < I

Based on the following observations, which of the activity series below correctly ranks these metals from most reactive to least reactive? a. no reaction occurs when the copper wire is placed in a solution of ZnCl2 b. a red-brown solid forms and a blue solution color fades when Zn is placed into CuSO4 c. Calcium dissolves instantaneously in cold water d. magnesium does not dissolve in cold water but requires the addiction of 3M HCl to dissolve e. Zinc requires concentrated HCl to dissolve f. Copper does not dissolve in concentrated HCl g. Particles of shiny solid appear when metallic Zn or Cu wire was placed in a solution of AgNO3

Ca > Mg > Zn > H2 > Cu > Ag

Metal activity series of 7 metals in this experiment

Ca>Mg>Al>Zn>Fe>Pb>Cu

Reacts with steam

Cd, Fe, Cr, Zn, Mn, Al, Mg

Strong bases/ group IIA metal hydroxides

CsOH, Ca(OH)2, Ba(OH)2, Sr(OH)2

Weak acids

H2CO3, HF, HCIO, H2SO3

Diprotic (2 protons)

H2SO4, H2CO3, H2C2O4

Triprotic (3 protons)

H3PO4, H3AsO4, H3C6H5O2

In the lab, you were given two unknown acids, each of which was able to separate SiO2 from CaCO3 using the filtration/dissolution/precipitation/decantation, etc. Which pair of acids were most likely present in the lab?

HCl and HNO3

Monoprotic (1 proton)

HCl, HNO3, CH3COOH, HI

Strong acids

HNO3, HCIO3, H2SO4, HCl, HBr, HCIO4, HI

Strong bases/ group 1A metal hydroxides

LiOH, NaOH, KOH, RbOH

Determine the identity of an unknown solid using the graph below

Lithium

Weak bases

NH3

Reacts with cold water

Na, Ca, Sr, Ba, K

H3PO4 + NaOH ------>

Na3PO4 + H2O

In the lab, a pair of students added solid NaHCO3 to 1M HCl in a test tube. The following observations were recorded in the students' notebook. Identify the products of the reaction.

NaCl (aq) + H2O (l) + CO2 (g)

Will the stoichiometric ratio be affected if the NaOH was added to the unknown acid instead of adding the unknown acid to the NaOH?

No

Copper is less reactive than hydrogen. What is the product(s) formed from the reaction between Copper (Cu) and hydrochloric acid (HCl)? a. none of the above b. Cu2+ (aq) + H2 (g) c. CuH2 (aq) + Cl2 (aq) d. Cu2+ (aq) + 2H+ (aq) e. Cl- (aq) + Cu2+ (aq) f. CuCl2 (aq) + H2 (g)

None of the above

Reacts with acids

Pb, Sn, Ni, Co

All of the following molecules are polar except: NH3 SO3 NO2- H2O SF4

SO3

Upon adding 0.75 g sulfuric acid to 0.85 M solution of NaNO2. you notice that there is a violent bubbling, a release of heat, and the formation of an orange-brown gas. Your lab partner isolates the gas in a stoppered test tube. The equilibrium for the orange-brown gas generated from the experiment is shown below. 2NO2 (g) -> N2O4 (g) ∆Hrxn < 0 orange-brown. colorless What would you observe upon placing the test tube with the colored gas in an ice bath?

The color would gradually fade

For the "Enthalpy of Formation of Ammonium Salts" experiment, ∆Hrxn = -∆Hsurroundings and ∆Hsurroundings =C∆T + mCs∆T, where C is the heat capacity of the coffee cup calorimeter and Cs is the specific heat of the solution. Choose the best explanation as to why you need to calculate the heat capacity for the coffee cup calorimeter before determining ∆Hrxn for the reaction of a strong base with a weak acid?

The heat released/absorbed from the reaction is absorbed/released by both the solution and the coffee cup calorimeter

In the lab, NaCl was isolated from SiO2 and CaCO3 by dissolving it in distilled water. If CaCO3 is slightly soluble in water (0.001g/100 mL), what will be the effect of the mass of each component isolated in the experiment?

The mass of NaCl will be greater than, the mass of CaCO3 will be less than the true value and the mass SiO2 will not be affected.

You are working in a lab and your TA gives you a yellow colored solution at equilibrium. The solution contains unknown concentrations of the chemicals in the reaction below. You then add 6.00 mL of 3 M sodium hydroxide to the solution. Predict what your observation would be and select the explanation as to why this would occur. CrO4 2- (aq) + H3O+ (aq) <--> Cr2O7 2- (aq) + H2O(l) yellow. orange

The solution stays yellow because the addition of sodium hydroxide decreases H3O+ concentration in the solution, thereby causing the pH to increase, causing the reaction to shift toward the reactants

Ti + 2HCl ---> TiCl2 + H2

Ti is oxidized H is reduced

A student determined that a molecule had a "square planar" molecular geometry. Which of the following molecules did she analyze?

XeF4

A solution of zinc chloride was titrated to the EBT end-point using 50 mL of 0.400 M EDTA. The student calculated the mass of chloride to be 0.355g. Determine the empirical formula of zinc chloride based on the data collected. Zn2+(aq0 + EDTA4- (aq) -> [ZnEDTA]2- (aq)

Zn2Cl

Which metal ion(s) below would you expect to form a colorless solution?

Zr4+, 1 only

C + D ----> A + B

backward reaction

A + B ----> C + D

forward reaction

Reduction

gain of electrons

The less reactive metal is the metal that is always

gaining electrons

the net differences in electronegativity are not close to 0

polar

"like dissolves like"

polar compounds dissolve other polar compounds, etc

solve for heat

q=mc∆T

Alkali metals (group I) salts

soluble

C2H3O2- (Acetate) salts

soluble

Cl- (chloride) Br- (bromide) and I- (iodide) UNLESS compounds of Ag+, Hg2+, and Pb2+

soluble

NH4+ (Ammonia)

soluble

NO3- (Nitrate) salts

soluble

SO42- (sulfate) UNLESS compounds of Sr2+, Ba2+, Hg2 2+, Pb 2+

soluble