Chem Lab I Final

Labs (I, II, III)

Labs (IV, V, VI)

Labs (VII, VIII, IX)

Labs (X, XI)

Quiz Questions

100

What is the density formula?

Density = mass/ volume

100

Name one of the gases from Lab IV that is toxic. If you name one that has a specific smell describe it.

NO₂, Cl₂(Pungent) , SO₂ (Choking odor as from matches), H₂S (Rotten Egg odor)

100

What is the STP? What is the Accepted Value of R?

STP: P = 1 atm, T = 0 celcius, R = 0.08206

100

What is Gravimetric Analysis?

Where a desired ion or compound is precipitated from a solution, and the mass of the precipitate is measured to determine the amount of the substance in the original sample.

100

The following elements are in order of decreasing reactivity to reducing agents: Ca, Cr, Zn, Co, Cu. Will a reaction occur between Cr(s) + Cu(NO₃)₂(aq)?

Yes because Cr has a pretty high reactivity rate and Cu(NO₃)₂ is aqueous.

200

What are the volume conversions involved in Lab I?

1 mL, 1 cm³, 1 CC

200

Which is most reactive with HCl (Zn, Fe, Ca, Mg)? Please list in order which is most reactive.

Ca, Mg, Zn, Fe

200

What are the three laws we observed in Lab VIII?

Boyle's Law: Pressure and volume are indirectly proportional.

P₁V₁ = P₂V₂

Charles' Law: @ constant pressure, the volume of a given mass of gas is directly proportional to the Kelvin

V₁/T_{1 =}V₂/T₂

Amonton's Law: @ constant volume, the pressure of a given mass is directly proportional to Kelvin.

P₁/T₁= P₂/T₂

200

In lab XI, we looked at the heat of neutralization. For the heat of neutralization of HCl(aq) + NaOH(aq) how do we calculate the energy released (kJ per mol) from water formed

E = - (E_total / mol_h_2o)

200

A small amount of solid containing one of the following anions: Carbonate, Chloride, Iodine, and Sulfate was placed in a small dry test tube. Upon adding concentrated sulfuric acid, no reaction was observed.

a. Based on the observation, what anion is probably present in the unknown?

b. What further test would be done to confirm your answer? (Indicate what reagent would be added to the original sample, and what you would observe.)

c. If the unknown was a lithium salt of the anion, write a balanced equation for the reaction. Indicate the phase of each species in the balanced equation

a. Sulfate because it produces no obvious smell or change odor

b. You would add water and Nitric acid to make it more acidic and add BaCl2(aq). White precipitate of BaSO₄.

c. 2LiCL (aq) + H₂SO₄ -> Li₂So₄ (aq) + 2HCl(g)

300

What are the mixtures we used in Lab II, and how did we separate them all?

NH₄Cl, NaCl, SiO

We used sublimation to separate NH₄Cl from the NaCl and SiO. We used extraction with water to separate NaCl from SiO, and we finally used decantation to get SiO separately.

300

What are the driving forces from Lab V? Give an example and write the molecular, complete, and net ionic equation.

Formation of a Precipitate

Formation of a Gas

Formation of a Weak Electrolyte

300

In Lab VI, what is the order of the reactions?

1. Redox

2. Metathesis (formation of precipitate)

3. Decomposition

4. Metathesis (dissolving precipitate)

5. Redox (single displacement)

300

How do you find the mass of Fe in the original sample?

Mass of precipitate x the gravimetric

300

In lab IX, a student finds that Rmax =0.0829 l atmmol k and Rmin =0.0819 l atmmol k.

a. Using these values, determine the average value of R and its uncertanity

b. calculate the precent difference of the average value of R and hte accepted value of R.

R = 0.08240.0005 L

0.0824-0.08210.0821100% = 0.365%

400

For Lab III, we used baking soda, NaHCO3. Write what the initial test is (the complete equation). What is the initial test? What is the new equation? What is the confirmatory test? What is the observation after the confirmatory test? What is the final balanced equation?

a. NaHCO₃(s) + H⁺(aq) -> CO₂(g) + H₂O(l) + Na⁺ (aq)

b. Initial test: Add H₂SO₄

c. Observation: Bubbling, Colorless odorless gas (CO₂), warm to the touch

d. 2NaHCO₃ (s) + H₂SO₄(l) -> CO₂(g) + H₂O(l) + Na₂SO₄(aq)

e. Confirmatory test: Suspended drop of Ba(OH)₂(aq)

f. Observation: Presence of CO₂ results in a cloudy, white precipitate

g. CO₂(g) + Ba(OH)₂(aq) -> BaCO₃(s) + H₂O (l)

400

From Lab IV, finish the equation and identify the driving forces: (NH₄)₂CO₃(aq) + 2HNO₃(aq)

(NH₄)₂CO₃(aq) + 2HNO₃(aq) ->2NH₄NO₃(aq) + CO₂(g) + H₂O (l)

CO₂ and H₂O are driving forces

400

What is the van Der Waals equation

R=(P+n2aV2)(V-nb)/nT

400

what is the equation to find the heat gained by the calorimeter?

(change in t mix x heat capacity of calorimeter)

400

In Lab III, Smelling Salts (NH4)2CO3(aq) are an example of a compound containing the ammonium ion.Write the balanced equation for the decomposition of smelling salts including phase labels. Most litmus paper can detect one of the products for this reaction. Which color litmus paper should be used and what observations do you expect?

(NH4)2CO3(s) -> 2NH3(g) + CO2(g) +H2O(g)

Red -> Blue

500

We also used Sodium Iodide in Lab III. What is the initial test? What is the first observation? (what is the complete equation) What is the confirmatory test? What is the observation after the confirmatory test? (What is the complete equation?)

a. Initial Test: add H₂SO₄

b. Observation: Violet vapors of I₂, a foul smelling gas is formed (NaI(s) + H₂SO₄(l) -> Complex R_xn (I₂(g) , H₂S(g) , HI (g) etc....)

c. Confirmatory Test: Dissolve in water, add nitric acid to acidify, add AgNO₃ (aq)

d. Observation: Presence of I^- results in an off white precipitate of AgI (NaI(aq) + AgNO₃ (aq) -> AgI(s) + NaNO₃(aq))

500

List the Water Solids (both soluble and insoluble and their colors)

Water-Soluble Solids

KCl - white (colorless solution)

NH₄Cl - White (colorless solution)

KMnO₄- purple

MnCl₂ - Pink (very pale)

Cu(NO₃)₂ - blue

Water-Insoluble Solids

CuS- very dark blue or black

Cu₂S - black

BaCrO₄ - Yellow

BaCO₃- white

PbCl₂ - White

MnO₂ - black or brown

500

For Lab VI, write all the chemical reactions and the observations

Know all 5 reactions and equations (be able to balance the equation if given etc)
Cu(s) + 4HNO3(aq) Cu(NO3)2 (aq) +2NO2(g)+2H2O(l) Cu(s) + 4H+(aq) +2NO3-(aq) Cu2+(aq, blue) + 2NO2(g) + 2H2O(l)

Redox

Observation : Cu dissolves producing a pungent, brown gas (NO2 )(g). Solution turns green then blue on adding water (blue signifies Cu)

Cu(NO3)2(aq) +2NaOH (aq) Cu(OH)2(s)+2NaNO3(aq)

Cu2+(aq, blue) + 2OH-(aq) Cu(OH)2 (s, light blue)

Metathesis (formation of precipitate)

Observation: Blue solution forms a cloudy, light blue mixture; the light blue color is due to a precipitate suspended in a colorless solution.

Cu(OH)2(s, light blue )CuO(s, black) + H2O(g)

Decomposition (dehydration)

Observation: On heating with stirring, the light blue, cloudy mixture forms a black solid in a colorless solution. Steam is released due to the evaporation of water.

CuO(s, black) + H2SO4(aq) CuSO4(aq, blue) + H2O(l)

CuO(s, black) + 2H+ (aq) Cu2+(aq, blue) + H2O(l)

Metathesis (dissolving precipitate)

Observation: The black solid dissolves forming a medium blue solution.

CuSO4(aq)+Zn(s)ZnSO4(aq) + Cu(s)

Cu2+(aq, blue) + Zn(s) Zn2+(aq) + Cu(S, red-brown)

Redox (single displacement)

500

Calculate the gravimetric factor, calculate the mass of Hg²⁺ in the precipitate, and calculate the % Hg²⁺ ion in the original sample. using this example. If a given water sample weighing 3.0243 is suspected of being contaminated with mercury, adding a solution of sodium hydroxide precipitates Hg²⁺ as HgO in a weighable formate following the reaction: Hg(C₂H₃O₂) (aq) + 2NaOH(aq) -> HgO(s_ + H₂O(l) + 2NaC₂H₃O₂(aq). The precipitate mercury (ii) oxide weighs 1.2156g.

1. 0.9261 g Hg²⁺/g HgO

2. 1.1258 g Hg²⁺

3. 37.23%

500

Write the balanced molecular, total ionic, and net ionic equation for the reaction between aqueous sodium acetate and sulfuric acid.

Molecular Equation:
1. 2NaC2H3O2(aq) + H2SO4Na2SO4(aq) + 2HC2H3O2(aq)
Total Ionic Equation:

2 Na+(aq)+ 2 C2H3O2(aq) + 2 H+(aq) + SO42-(aq) 2 Na+(aq) + SO42-(aq) + 2HC2H3O2(aq)

Net Ionic Equation:

C2H3O2(aq) + H+(aq) HC2H3O2(aq)