UGA chem 1211 lab practicle

Write the equation that represented the reaction that caused the bubbling when HCI reacted with the new penny?

Zn (s) + HCl (aq) —> H₂ (g) + ZnCl₂ (aq)

What type of reaction is Zn (s) + HCl (aq) —> H₂ (g) + ZnCl₂ (aq)?

A single displacement / Redox reaction

What is the equation used to calculate the percent composition of copper and zinc in a penny from the density of a penny?

density of the penny = (density of copper g/cm³ % of copper) + (density of zinc g/cm³ * % of zinc)

Density of copper = 8.92 g/cm³ Density of zinc = 7.14 g/cm³

density of the penny = (8.92 g/cm³ * x) + (7.14 g/cm³ (1-x))

How was density calculated for the old and new pennies in the counting pennies experiment?

d = m/v

The mass of each penny was obtained by weighing them. The volume of each pennies was obtained by filling a graduated cylinder with water and then placing the pennies inside, using the difference between the initial and final volume of the water to determine the final volume of the penny.

How do you read measurements in a graduated cylinder?

By reading the value at the bottom of the meniscus (lil semi circle thing) to all the degrees of certainty possible plus one more value of estimate

What do y and x represent in the linear regression equation for sugar content in beverages?

y = density x = sugar concentration

What is filtration

One component dissolves in water. Mixture is seperated by filter paper and filter funnel. Solid is collected on paper. Liquid that flows through is the filtrate

What is evaporation

Used when solid present in the liquid is non-volatile. Solution is heated. Solvent evaporates and solid is left as residue

What is chromatography

When dissolved in a solvent, different constituents will travel at different rates on paper and become seperated.

What is distilation

Process of seperating components from liquid mixtures through vaporization and condensation, based on different boiling points of components in the mixture

What is centrifugation

Use of cetrifugal force for the sedimentation of heterogenous mixtures

Sedimentation

When solid particles settle out. Heavier solid will go to the bottom of the slurry or suspension

What are the steps to use a volumetric pipet?

1. Place pipette into solution (not at surface and not touching the bottom) and roll knob downwards until the solution is a couple inches above the line

2. then, adjust the amount by rolling the knob upwards until the bottom of the meniscus is at the graduation line

3. To release solution, place tip of the pipette on the edge of the flask and press the rectangular button on the side

4. Wait the amount of seconds on the pipette after the meniscus stops descending

alum or potassium alum

KAI(SO4)2 × 12 H2O

Mass percent of compound in a mixture Eq

mass of compound / mass of the full sample x 100

Percent composition of individual elements in a mixture

% composition of the element = (molar mass of element / molecular mass of compound) x mass percent of compound in mixture

Gas forming reactions

Metal carbonate salts react with acids to the corresponding metal salt, water and carbon dioxide gas

Ex: 2 HCl (aq) + CaCO₃ (s) → CaCl₂ (aq) + H₂O (l) + CO₂ (g) and HCl (aq) + NaHCO₃ (s) → NaCl (aq) + H₂O (l) + CO₂ (g)

In the first step to synthesize Alum, Aluminum metal was oxidized to AI³⁺ using a strong base to form an aluminate ion, Al(OH)₄ ^- and produce hydrogen gas

2 Al (s) + 2 KOH (aq) + 6 H₂O (l) —→ 2 KAI(OH)₄ (aq) + 2 H₂ (g)

In the second step to synthesize alum, a strong acid is added to 2 KAI(OH)₄ to form aluminum hydroxide

The initial reaction will be 2 KAI(OH)₄ + H₂SO₄ (aq) —→ 2 Al(OH)₃ (s) + 2 H₂O (l) + K₂SO₄ (aq)

After further reaction with the acid the Al(OH)₃ precipitate will dissolve : 2 Al(OH)₃ (s) + 3 H₂SO₄ (aq) —→ Al₂(SO₄)₃ (aq) + 6 H₂O

In the final step to synthesize alum, the aluminum ions combine with the potassium and sulfate ions to crystallize as a hydrated complex

KAl(SO₄)₂ × 12 H₂O - potassium alum

In the synthesis of alum experiment, barium nitrate was added to alum to verify the presence of sulfate since barium ions react with sulfate to form an insoluble compound. The equation for that reaction is

Ba²⁺ (aq) + SO₄ ^2- (aq) —→ BaSO₄ (s)

In the synthesis of alum experiment, red dye, called aluminon was added with ammonia to alum to test for Al³⁺. A solid, Al(OH)₃ should form. If pink, aluminum ions are present. The equation for that reaction is

Al³⁺ (aq) + 3 NH₃ (aq) + 3 H₂O (l) + aluminon ——> Al(OH)₃ * aluminon (s) + 3 NH₄⁺ (aq)

percent yield eq

percent yield = actual/theoretical x 100

In the equation for a linear regression curve for spectrometric analysis, what do the variables represent?

y = absorbance x = phosphate concentration and the slope (number before x) = represents molar absorptivity

Lambert Beer law

the absorbtion of light as it passes through a solution is proportional to the concentration of the absorbing species, the length of the light path, and a fundamental property of the material called the molar absorptivity

Lambert beer law eq

A = elc e = molar absorptivity l = length of the light path c = concentration

Once potassium aluminum sulfate dodecahydrate is added to the pond water, the negative charges on the water particles are neutralized by in organic coagulants and a aluminum hydroxide preticipate froms. Precipitates combine into larger particles through Brownian motion and flocculation and will eventually settle to bottom of flask. Phosphate ions will also settle into the bottom of the flask, redcuing the concentration of phosphate ions suspended in water

Copper sulfide is oxidized to form copper oxide

2 Cu₂S + 3 O₂ ——> 2 Cu₂O + 2 SO₂

Copper oxide is reduced to form elemental copper

2 Cu₂O ——> 4 Cu + O₂

single displacement reaction

one element replaces another in a compound

double displacement

Cations and anions of two different compounds switch positions

Decomposition

One substance breaks down two or more smaller substances

Combustion

Reaction involving oxygen and usually heat

Neutralization reaction

combination of an acid and a base

Redox reaction

Reaction where electrons are transferred between two or more substances

Precipitation reaction

Two or more substances combine to form one or more insoluble substances

Reaction one of the copper cycle: dissolving copper metal to make copper (II) ions

Redox reaction: Cu (s) + 4 HNO₃ (aq) —→ Cu(NO₃)₂ (aq) + 2 NO₂ (g) + 2 H₂O (l)

Reaction 2 of the copper cycle: Precipitating an insoluble hydroxide compound

Precipitation & Double Displacement reaction:

Cu(NO₃)₂ (aq) + 2 NaOH (aq) —→ Cu(OH)₂ (s) + 2 Na(NO₃) (aq)

Reaction three of the copper cycle: Dehydrate via heating

Decomposition reaction: Cu(OH)₂ (s) ——→ CuO (s) + H₂O (g)

The fourth reaction of the copper cycle: Formation of copper (ii) ions

Double displacement reaction: CuO (s) + H₂SO₄ (aq) ——→ CuSO₄ (aq) + H₂O (l)

Reaction 5a of the copper cycle: Reduction to form elemental copper

Single displacement reaction: CuSO₄ (aq) + Zn (s) —→ Cu (s) + ZnSO₄ (aq)

Reaction 5b of the copper cycle: Oxidation of zinc

Oxidation Reduction reaction: Zn (s) + 2 HCl (aq) ——→ ZnCl₂ (aq) + H₂ (g)

At the cathode *where reduction takes place* write the reaction equation

Zn ²⁺ (aq) + 2 e- ——→ Zn (s)

At the anode *where oxidation takes place* write the reaction equation

2 I ^- (aq) ——→ I₂ (aq) + 2 e-

Equation to calculate heat gained by the water in Calorimetry experiment

q = m(c)(delta T)

zinc iodide lab: what element does reduction take place in?

Zn

coagulant

A substance that causes a liquid to change to a solid or semisolid state

copper cycle lab: a copper sulfide ore is oxidized to form copper oxide followed by the reduction to form elemental copper. If the starting equation is
2CU2S + 3O2 --> 2CuO + 2SO2
what's the final equation in the production of copper?

2 CuO ——→ 4 Cu + O₂

When/ how was the white precipitate formed during the synthesis of alum experiment?

When H2SO4 was added to the filtrate (formed when using gravity filtration to separate solid from the dissolved Al and KOH), a white precipitate formed.
Al(OH)3 is the white precipitate

How were acids and bases used in the synthesis of alum experiment?

When H2SO4 was added to the filtrate (formed when using gravity filtration to separate solid from the dissolved Al and KOH), a white precipitate formed.
Al(OH)3 is the white precipitate

How did we test for the presence of sulfate in the alum?

Added barium nitrate to a small amount of dissolved alum (KAl(SO4)2)). Barium ions react with sulfate to form an insoluble compound. So if a precipitate formed when the barium nitrate was added, the presence of sulfate was confirmed.

What was the reference in the Analysis of Phosphate in Lake Water experiment composed of and used for?

Was composed of DI water and color enhancing solution. Was used to zero the spectrophotometer

Partial pressure formula used in gas measurements experiment

Ptot= P(CO2) + P(H2O) + (h/13.6)

In the Analysis of Phosphate in Lake Water experiment how was the Lambert-Beer Law applied?

A color indicator was added to the treated lake water sample. The greater the intensity of the yellow color, the more concentrated the phosphate solution.

In the Analysis of Phosphate in Lake Water experiment, what method was used to measure the phosphate concentration after treating the lake water with alum?

spectrophotometry

how did we separate zinc iodide into its elemental components

electrolysis

gas measurements and partial pressure lab: the volume of gas collected may be read to the _______________ place from the eudiometer tube

hundredth

gas measurements and partial pressure lab: what's the chemical equation for carbonate reacting with acid to produce carbon dioxide? (hint: more than just those three elements are in the equation)

CaCO3 + 2HCl --> CaCl2 + H2O + CO2

zine iodide lab: what element does oxidation take place in?

I

Accuracy of glassware??

Beakers and erlenmeyer flasks are approximate, volumetric flasks are exact

accuracy of a volumetric pipette???

HELLA exact