CHEM 054 Study Set

If the we know the ΔH of following equations, Fe2O3(s) + 3CO(g) = 2Fe(s) + 3CO2(g) ΔH1 = -26.7kJ/mol 3Fe2O3(s) + CO(g) = 2Fe3O4(s) + CO2(g) ΔH2 = -50.75kJ/mol Fe3O4(s) + CO(g) = 3FeO(s) + CO2(g) ΔH3 = -36.5kJ/mol Then what is the ΔH of reaction FeO(s) + CO(g) = Fe(s) + CO2(g) A. +7.28 kJ/mol B. -7.28 kJ/mol C. +43.68 kJ/mol D. -43.68kJ/mol

(A) + 7.28 kJ/mol need to use Hess's Law & manipulate the equations to cancel out coefficients to get final equation of interest - adding up all of the enthalpy values

Which statements about Enthalpy is correct? A. Enthalpy of a reaction can be measured through calorimetry. B. Heat from a reaction (qrxn) equals to ΔH°rxn. C. ΔH is positive for the reaction: 2H2O → 2H2 + O2.

(C) ΔH is positive for the reaction: 2H2O → 2H2 + O2 --> breaking more bonds than forming bonds so positive enthalpy value (A) is false bc while we can get the direct heat value from calorimetry, we need to solve it per mole to actually get the enthalpy (B) is false bc enthalpy is heat per mole

C(s) + O2(g) = CO2(g) ΔH1 CO2(g) + C(s) = 2CO ΔH2 2CO(g) + O2(g) = 2CO2(g) ΔH3 4Fe(s) + 3O2(g) = 2Fe2O3(s) ΔH4 3CO(g) + Fe2O3(s) = 3CO2(g) + 2Fe(s) ΔH5 Which one of the following is true? A. ΔH1 > 0, ΔH3 < 0 B. ΔH2 > 0, ΔH4 > 0 C. ΔH1 = ΔH2 + ΔH3 D. ΔH3 = ΔH4 + ΔH5

(C) ΔH1 = ΔH2 + ΔH3 need to go through and actually solve the answer choices by manipulating the reaction equations to see which one fits (just need to look at sign)

Things to consider when naming ligands

- if the ligand is monodentate, there is no need to specify that it's chelating bc it's already assumed that it can only bond with one metal - the more single bonds the more flexible the compound is so more likely to be chelating

How many unpaired electrons are found in Zn(H2O)62+?

0

How many unpaired electrons are found in Fe(en)32+ (strong field)?

2

How many unpaired electrons are found in Mn(CN)63- (strong field)?

2

How many unpaired electrons are found in NiBr42- (tetrahedral)?

2

When one mole of a substance is formed from its constituent elements in their standard states at standard conditions, ΔH for the reaction is called the standard heat of formation and given the symbol ΔHf. What is the temperature for standard conditions?

298.15 K The standard enthalpy of formation is defined as the change in enthalpy when one mole of a substance in the standard state (1 atm of pressure and 298.15 K) is formed from its pure elements under the same conditions

In the complexes we made, how many bonds does copper form to ligands?

4

Diamagnetic

All electrons are paired

In the spectroscopy portion, you utilized a copper-________ complex because it is a darker blue that is better for spectroscopy applications than a copper-water complex.

Ammonia

When measuring ΔH of solvation for salt A and B, you got ΔHA = -40 kJ/mol and ΔHB = 20 kJ/mol. It is most likely that ______ is for cold packs and ________ is for hot packs. (Fill "A" or "B" in the blanks.)

B is for hot packs bc if the solvation of the salt had positive enthalpy, it lost heat from system and the surroundings gained heat A is for cold packs bc with negative enthalpy heat is being gained by the reaction and lost from the surroundings

A ligand that forms two or more bonds to separate metal centers is said to be ___________?

Bridging

A ligand that forms two or more bonds to a single metal center is said to be ___________?

Chelating

True or False: In the MgO + HCl reaction, all of the heat of the reaction is absorbed by the water in which the reaction takes place.

False experiment set up calorimeter with temperature vernier log pro probe - put HCl solution in calorimeter then Mg ribbon which once added increased the temperature - statement is false bc not all of the heat of the reaction is absorbed by the water and some of the heat is absorbed by the calorimeter

During an exothermic reaction, heat goes into the system which causes the temperature of the liquid surrounding the system to increase. True or False?

False - in an exothermic reaction heat should leave the system and go into the surroundings, making the temperature of the liquid surrounding the system increase

True or False? The kinetic product, the product that forms the quickest is always the most stable product.

False - wrong to assume that it's always the most stable product - the thermodynamic product could be more stable bc lower product energy

A good calorimeter will have _________ insulation and ___________ heat capacity.

GOOD INSULATION = not allowing heat to transfer between calorimeter and surroundings LOW HEAT CAPACITY = do not absorb that much heat

In lecture, we observed the gummy bear reaction, and discussed the energy of a reaction as being represented by ______ and _____ .

Heat and light

Consider the following equation: qrxn = -qliq = -[ CcalΔT + (m)(c)(ΔT)] = nΔH°rxn What does ΔH°rxn in this case represent?

Heat evolved by the reaction - enthalpy of the reaction - delta H is the molar quantity of the heat flow (q) to and from the reaction

What is one main advantage of using a parallel dilution technique?

No error propagation

Small ions may have ____ interactions with water and _____ forces between ions than larger ions.

Stronger and stronger Coulomb's Law - smaller ions reduce the distance and bc they're charged they'll have stronger interactions and attractions with other ions and water

You created a standard curve and calculated the slope to be 65.09. After synthesizing your copper network, you weighed 0.052 grams of your copper product, worked it up with nitric acid, buffer, and ammonia and added it to a 25 mL volumetric flask. Then, you measured the absorbance of your solution and received a value of 0.385. What is the % mass of copper in your product?

Take the absorbance and divide it by the slope to get the concentration - then use the concentration and the volume of the flask (25 mL) to find the moles of copper and further the mass of the copper in the sample - take the mass of copper and divide by the mass of copper product (0.052 g) and multiply by 100 to get the mass %

In order to calculate the heat given off by an exothermic reaction, we measure the change in?

Temperature - during the exothermic reaction heat is transferred to two places (1) reaction mixture which can be measured as a temperature rise, and (2) the walls of the calorimeter

What is the geometry around the copper centers?

Tetrahedral - Copper (I) complexes tend to be tetrahedral because the tetrahedral configuration is favorable to smaller orbital transitions and requires less energy. It will take less energy to fill the orbitals with the 10 d electrons the metal has because there is less splitting and less distance between the orbitals.

Which of the following statements is true of the crystal field model?

The ligands are treated as negative point charges.

Which standard is used to measure the λmax?

The most concentrated standard

How can you tell which product is thermodynamically favored?

The product with the lowest product energy at the end of the reaction

How can you tell which product is kinetically favored?

The product with the smallest activation energy

True or False? When using the equation: qreaction=−mcΔT for the salt reactions this week, the mass used is the mass of the salt plus the mass of the water.

True

True or False? When considering charge and size in determining interactions between ions and ions and water, we consider charge first and then look at size.

True - greater the charge the stronger the interactions

True or False? For a given reaction, we have qrxn = - (qliq + qcal ). If qliq and qcal are positive values, then this reaction must be exothermic.

True - liquid and calorimeter are the surroundings of the reaction - remember that what ever heat is absorbed/released by the reaction (which is the system), the heat done to the surroundings has to be the opposite

The spectrochemical series isI- < Br- < Cl- < F- < OH- < H2O < NH3 < en < NO2- < CN- Which of the following complexes will absorb visible radiation of the highest energy (shortest wavelength)?

[Co(en)3]3+ has strongest field out of the answer choices meaning more splitting and higher energy

The surroundings ________ energy if the reaction enthalpy has a negative value.

absorb

Energy is absorbed/released (pick one) when bonds are broken.

absorbed

Paramagnetic

at least one electron is unpaired

True or False? If more energy is used to break up ionic lattice than energy released as ions form interaction with water molecules, ΔHreaction > 0.

bc more energy used to break bonds - usually the bonds ions form with water molecules are weaker

For an endothermic process, more energy is invested in _________ bonds.

breaking

Ligands ___________ electrons when interacting with a metal.

donate

If you ignore Ccal when measuring the ΔHreaction of an endothermic reaction, your measured value would be more/less (pick one) endothermic than the true value.

less - if we would plug the values into the q equation which would be used to find the enthalpy and we ignore the calorimeter value, the q value we get or "measure" is going to be much less than the one with the calorimeter value so if the q value is less the delta H value will be less and so less endothermic (positive delta H - it would be opposite for exothermic)

A coordination compound of Cu2+ can be described as Cu(NH3)xSO4 and is known to contain 29.9% NH3. What is the value of x?

need to figure this out

If 0.224 grams of MgO were added to 25 mL of HCl (assume a density of 1.00 g/mL), use the graph collected below to calculate the heat of the reaction in Joules (Ignore Ccal).

not on skills check

In a standard endothermic system, qrxn __ 0 and qliq __ 0 since the system absorbs energy.

qrxn > 0 bc the system, which is the reaction, is absorbing energy, and qliq < 0 bc it's the surroundings which is opposite of the system

The reusable hot pack is filled with __________.

sodium acetate

Bridging

when the bonds from the same ligand are formed with different metals

Chelating

when the bonds from the same ligand are formed with the same metal