The pKb values for the dibasic base B are pKb1 = 2.10 and pKb2 = 7.37. Calculate the pH at each of the following points in the titration of 50.0 mL of a 0.55 M B(aq) with 0.55 M HCl(aq).

(a) before addition of any HCl

(b) after addition of 25.0 mL of HCl

(c) after addition of 50.0 mL of HCl

(d) after addition of 75.0 mL of HCl

(e) after addition of 100.0 mL of HCl

You have 625 mL of an 0.23 M acetic acid solution. What volume (V) of 2.10 M NaOH solution must you add in order to prepare an acetate buffer of pH = 5.03? (The pKa of acetic acid is 4.76.)

A 0.5206 g solid sample containing a mixture of LaCl3 (molar mass = 245.26 g/mol) and Ce(NO3)3 (molar mass = 326.13 g/mol) was dissolved in water. The solution was titrated with KIO3, producing the precipitates La(IO3)3(s) and Ce(IO3)3(s). For the complete titration of both La3 and Ce3 , 43.38 mL of 0.1236 M KIO3 was required. Calculate the mass fraction of La and Ce in the sample.​

Fill in the blanks

1. the ____ atoms of the ____ groups and the hydrogen atoms attached to the ____ atoms form ____.

(answer choices; nitrogen, carbon, a-helices or b-pleated sheets, carbonyl, globular of firbrous structures, oxygen, amino, random coil, thiol)

2. In the a helix, hydrogen bonds form between the ____ oxygen atom and the ____ hydrogen atom of a peptide bond in _____. In the B-pleasted sheet, hydrogen bonds form between the ____ oxygen atom and the ____ hydrogen atom of a peptide bond in ____.

(answer choices; parallell sections of a long polypeptide chain, the next amino acid unit, carboxyl, the next turn of the helical chain, thiol, amino, carbonyl)

What are some of the key characteristics of unknown sample of an aqueous solution containing an ionic compound?

Specific questions:

1. Given that the cation is from Group 1A, what is the identity of the group 1A metal ion in your solution?

2. Given that the ionic compound contains either chloride or hydroxide, how can you determine which? (Two pieces of evidence are required and one must be related to solubility rules)

3. What is the concentration of your solution? (Your unknown sample is known to be about 1 M, but you need to determine the concentration to 3 significant figures using titration. You should plan ahead so that you know approximately what volume of your sample you will need in order to use approximately 25 mL of 0.100 M sulfuric acid for the titration).

I'm confused as to how I would go about figuring out these things when even actual information.

The enthalpy of combustion, ΔH, for benzoic acid, C₆H₅COOH, is -3226 kJ/mol. When a sample of benzoic acid was burned in a calorimeter (at constant pressure), the temperature of the calorimeter and contents rose from 23.20°C to 28.40°C. The heat capacity of the calorimeter and contents was 12.41 kJ/ °C. What mass of benzoic acid was burned?

1.(a) What is a chain reaction?

(b) Why is monobromination of ethane a more practical reaction than the monobromination of propane?

(c) Write the mechanism involved in the chain reaction of monbromination of propane. State the experimental conditions, major and minor products.

Name each of the steps. Explain your answer.

(d) Draw the bond-line formula of 3,4-dimethylhexane.
Is geometric isomerism observed in 3,4-dimethylhexane?
What structural features must be present for stereoisomers to exist?

thanks

1. Calcium oxalate monohydrate, CaC2O4•H2O, is stable up to ~100˚C, but will release the incorporated water molecule when heated to 300˚C, according to the following reaction:

CaC2O4•H2O(s) → CaC2O4(s) + H2O(g)

If a 4.1754 g sample of calcium oxalate monohydrate is heated to 300˚C, what should be the mass (g) of the resulting calcium oxalate?

2. An unknown sample of ore with a mass of 506.1 g is allowed to react with excess magnesium and ammonia, NH3, in order to analyze for phosphate, PO43-, according to the following precipitation reaction:

2PO43-(aq) + 2Mg2+(aq) + 2NH3(aq) + 2H2O(l) → Mg2(P2O7)(s) + 2NH3(aq) + 2OH-(aq) + H2O(l)

After the precipitated Mg2(P2O7) is carefully rinsed and dried, the mass is determined to be 0.09870 mg.
Assuming all phosphorous originally present in the ore was in the form of phosphate, what was the original mass (μg) of phosphorous in the ore sample?

3. An unknown organic compound was produced by students in the O-chem lab. According to their records, this compound should only contain carbon and hydrogen atoms. A combustion analysis is performed on the sample.

When 0.1727 g of the sample is burned in the presence of excess oxygen, the magnesium perchlorate cartridge increases 0.24889 g and the ascarite cartridge increases 0.53094 g.

What is the percent C (w/w) in the sample?

4. What is the percent H (w/w) in the sample?

5. What is the empirical formula for the unknown compound?

Consider the reaction

Mg(s)+Fe2+(aq)→Mg2+(aq)+Fe(s)

at 63 ∘C , where [Fe2+]= 2.90 M and [Mg2+]= 0.210 M .

Part A

What is the value for the reaction quotient, Q, for the cell?

Express your answer numerically.

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Part B

What is the value for the temperature, T, in kelvins?

Express your answer to three significant figures and include the appropriate units.

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Part C

What is the value for n?

Express your answer as an integer and include the appropriate units (i.e. enter mol for moles).

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Part D

Calculate the standard cell potential for

Mg(s)+Fe2+(aq)→Mg2+(aq)+Fe(s)

Express your answer to three significant figures and include the appropriate units.

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Part E

What is the cell potential for the reaction

Mg(s)+Fe2+(aq)→Mg2+(aq)+Fe(s)

at 63 ∘C when [Fe2+]= 2.90 M and [Mg2+]= 0.210 M .

Ozone gas, O3 decomposes into O2 in presence of NO and gaseous O atoms The following data was obtained Determine the experimental rate law for the reaction given the following data and the value for the rate constant

O 3= 2.3 x 10^-4 atm NO = 1.6 x 10^-4 O = 1.5 x 10^-4 rate1 = 2.6 x 10-3

O3 = 2.3 x 10^-4 NO = .8 x 10^-4 O = 1.5 x 10^-6 rate 2 = 1.3 x 10^-3

O 3 = 4.6 x a0^-4 NO = 1.6 x 10^-4 O = 1.5 x 10^-6 rate 3 = 5.2 x 10^-3

O3 = 4.6 x 10^-4 NO = 1.6 x 10^-4 O = 3.0 x 10^-6 rate 4 = 5.2 x 10^-3

What is the predominant intermolecular force in the liquid state of each of these compounds: ammonia (NH3), carbon tetrachloride (CCl4), and hydrogen sulfide (H2S)? Drag the appropriate items to their respective bins.

Consider a system consisting of a cylinder with a movable piston containing 10⁶ gas molecules at 298 K at a volume of 1 L. Consider the following descriptions of this system:

A. Initial system as described above.

B. Starting from the initial system, the volume of the container is changed to 2 L and the temperature to 395 K.

C. Starting from the initial system, a combination reaction occurs at constant volume and temperature.

D. Starting from the initial system, the gas reacts completely to produce 10⁷ gas molecules at 395 K in a volume of 2 L.

Arrange the descriptions in order of increasing number of microstates in the resulting system. Explain the rationale for your ranking.

Is this ranking the same order as if you ranked the systems according to increasing entropy?  

What are the three basic types of solids and the composite units of each? What types of forces hold each type of solid together?

Applying the phase rule. Consider the phase diagram for a one-component system.

(a) What is the variance and number of phases at (T1, p1)?

(b) What is the variance and number of phases at (T2, p2)?

(c) What is the variance and number of phases at (T3, p3)?

(d) Which is the triple point?

What volume of each of the following acids will react completely with 50.32 mL of 0.120 M NaOH?

(a)    0.130 M HCl
mL

(b)    0.180 M H₂SO₃ (two acidic hydrogens)
mL

(c)    0.210 M H₃PO₄ (three acidic hydrogens)
mL

(d)    0.135 M HNO₃
mL

(e)    0.255 M HC₂H₃O₂ (one acidic hydrogen)
mL

(f)    0.320 M H₂SO₄ (two acidic hydrogens)
mL