What is protein denaturation?

What is protein denaturation?

Denaturation involves the disruption of the native confirmation or shape (secondary and tertiary structures) of the protein molecules keeping the primary structure intact. Since the native conformation of protein is essential to its biological activity, denaturation destroys the ability of a protein molecule to function properly. Denaturation, most of the time, causes coagulation or precipitation of proteins.

Explain the xanthoproteic test. What can the xanthoproteic test be used for?

Explain the xanthoproteic test.

Almost all proteins will give a positive test, but only the three amino acids containing aromatic rings will give positive tests (tyrosine, phenylalanine, tryptophan). Yellow colored products due to undergoing nitration when treated with concentrated HNO3 for a positive test (nitration reaction). Since skin is made up of protiens if concentrated HNO3 is spilt on it it will undergo nitration and turn yellow.

What can the xanthoproteic test be used for?

To determine if something is/contains a protein or has an amino acids containing aromatic rings (tyrosine, phenylalanine, tryptophan)

Explain the ninhydrin reaction. What can the ninhydrin test be used for?

Explain the ninhydrin reaction.

Amino acids are oxidized to aldehyde and ammonia when heated. The liberated ammonia reacts with ninhydrin to produce an intense blue to purple color. The free amino groups on the N terminal end of proteins and peptides also give rise to ammonia to give the characteristic color with ninhydrin. Both amino acids and proteins give a positive test with ninhydrin reagent. Use to locate the amino acids in the technique of paper chromatography.

What can the ninhydrin test be used for?

To distinguish if there are amino acids or protiens present

Explain the Biuret Test? What can the Biuret Test be used for?

Explain the  Biuret Test?

It identifies the presence of peptides and proteins. A minimum of two peptide bonds (tripeptide) are required for a positive test. A tripeptide will give a pale violet color when treated with an alkaline solution of dilute copper (blue). Used for both qualitative and quantitative estimation of proteins. Amino acids and dipeptides will NOT give a positive biuret test.

What can the Biuret Test be used for?

Since amino acids do not give positive tests, this can be used to distinguish proteins from amino acids.

Raising the temperature of the reaction mixture will:

Raising the temperature of the reaction mixture will:

a. cause [CO2] to increase c. have no effect
b. cause [H2O] to increase d. cannot be determined


Answer: b. cause [H2O] to increase

Addition of CO to an equilibrium mixture of the above reaction will

Addition of CO to an equilibrium mixture of the above reaction will

a. cause [CO2] to increase c. have no effect
b. cause [H2O] to increase d. cannot be determined


Answer: a. cause [CO2] to increase

If you mixed 5.0 mol CO2, 0.10 mol H2, 3.5 mol of CO, and 0.0010 mol H2O in a one-liter container, in which direction would the reaction proceed?

If you mixed 5.0 mol CO2, 0.10 mol H2, 3.5 mol of CO, and 0.0010 mol H2O in a one-liter container, in which direction would the reaction proceed?

a. To the left.
b. To the right.
c. The above mixture is the equilibrium mixture.
d. Cannot tell from the information given.


Answer: b. To the right.

The equilibrium constant, Kc, for the following reaction is 1.20 x 10-2 at 500K: PCl5(g) PCl3(g) + Cl2(g). Calculate Kp for this reaction.

The equilibrium constant, Kc, for the following reaction is 1.20 x 10-2 at 500K: PCl5(g) PCl3(g) + Cl2(g). Calculate Kp for this reaction.

a. 0.0120
b. 0.492
c. 49.9
d. 20.2
e. 7.13 x 10-6


Answer: b. 0.492

If an equilibrium mixture of the three gases in a 5.0L container at 298K contains 0.304mol of NOBr gas and 0.401mol of Br2 gas, what is the equilibrium concentration of NO?

The equilibrium constant, K, for the following reaction is 6.50 x 10-3 at 298K

2NOBr(g) 2NO(g) + Br2(g)

If an equilibrium mixture of the three gases in a 5.0L container at 298K contains 0.304mol of NOBr gas and 0.401mol of Br2 gas, what is the equilibrium concentration of NO?

a. 6.14 x 10^-2 M
b. 3.74 x 10^-3 M
c. 4.93 x 10^-3 M
d. 1.73 x 10^-2 M
e. 3.00 x 10^-4 M


Answer: d. 1.73 x 10^-2 M

Which of the following statements is true about the above reaction?

The equilibrium constant, K, for the following reaction is 1.96 x 105 at 548K

NH3(g) + HCl(g) NH4Cl (s)

Which of the following statements is true about the above reaction?

a. The reaction favors the products and the concentrations of NH3 and HCl will be low at equilibrium.
b. The reaction favors the reactants and the concentrations of NH3 and HCl will be high at equilibrium
c. The reaction favors the product and the equilibrium concentration of NH4Cl equals 1.
d. The reaction favors the reactants and the equilibrium concentration of NH4Cl equals 1.
e. Two of the above are true.


Answer: a. The reaction favors the products and the concentrations of NH3 and HCl will be low at equilibrium.

Dinitrogen tetraoxide exists in equilibrium with nitrogen dioxide: N2O4(g) 2NO2(g). At a certain temperature, K = 6.98 x 104. Which of the following statements is true about this reaction?

Dinitrogen tetraoxide exists in equilibrium with nitrogen dioxide: N2O4(g) 2NO2(g). At a certain temperature, K = 6.98 x 104. Which of the following statements is true about this reaction?

a. the concentration of NO2 is equal to the concentration of N2O4 at equilibrium
b. the rate of dissociation of N2O4 is equal to the rate of formation of NO2 at equilibrium
c. the reaction will reach equilibrium rapidly
d. the rate constant for the forward reaction is equal to the rate constant for the reverse reaction at equilibrium
e. two of the above


Answer: b. the rate of dissociation of N2O4 is equal to the rate of formation of NO2 at equilibrium

The reaction between lead ion and chloride ion is: Pb2+(aq) + 2Cl-(aq) PbCl2(s). If K = 2.57 x 107 for this reaction, what is the value for the equilibrium constant for the reaction: 2PbCl2(s) 2Pb2+(aq) + 4Cl-(aq)?

The reaction between lead ion and chloride ion is: Pb2+(aq) + 2Cl-(aq) PbCl2(s). If K = 2.57 x 107 for this reaction, what is the value for the equilibrium constant for the reaction: 2PbCl2(s) 2Pb2+(aq) + 4Cl-(aq)?

a. 3.89 x 10^-8
b. 6.60 x 10^14
c. 1.51 x 10^-15
d. 5.07 x 10^3
e. 1.97 x 10^-4


Answer: c. 1.51 x 10^-15

Which of the following is true about a chemical equilibrium?

Which of the following is true about a chemical equilibrium?

a. It is microscopically static and macroscopically dynamic.
b. It is microscopically dynamic and macroscopically static.
c. It is microscopically and macroscopically static.
d. It is microscopically and macroscopically dynamic.


Answer: b. It is microscopically dynamic and macroscopically static.

What color will the indicator change when NaOH is added?

An indicator, HIn, shows a color change from blue to yellow, depending on the acidity of the solution:

HIn (aq) H+ (aq) + In- (aq)
(blue) (yellow)

What color will the indicator change when NaOH is added?

a. blue
b. yellow
c. no color change


Answer: b. yellow

Kc = 2.90 x 10-2 and ΔHo = 198 kJ/mol at 1150K. Which of the following changes will favor the production of SO2?

Consider the following system at equilibrium:

2SO3(g) 2SO2(g) + O2(g)

Kc = 2.90 x 10-2 and ΔHo = 198 kJ/mol at 1150K. Which of the following changes will favor the production of SO2?

a. Increasing the temperature
b. Increasing the pressure
c. Adding O2 gas
d. Adding sulfur, S
e. Adding a catalyst


Answer: a. Increasing the temperature

Calculate the equilibrium partial pressure of (CH3)2CHOH when (CH3)2CHOH is introduced into an evacuated flask at a pressure of 1.04 atm at 452K.

The equilibrium constant, Kp, for the following reaction is 4.44 x 10-4 at 452K.

(CH3)2CHOH(g) (CH3)2CO(g) + H2(g)

Calculate the equilibrium partial pressure of (CH3)2CHOH when (CH3)2CHOH is introduced into an evacuated flask at a pressure of 1.04 atm at 452K.

a. 0.000462M
b. 0.0207M
c. 0.0215M
d. 1.02M
e. 1.039M


Answer: d. 1.02M

A reaction mixture was found to contain 0.0381 moles of HI, 0.0471 moles of H2, and 0.0364 moles of I2 in a 1.00 L container. Is the reaction at equilibrium? And if not, what direction must it run in order to reach equilibrium?

Consider the following reaction where Kc = 1.18 at 150K:
2HI(g) H2(g) + I2(s)

A reaction mixture was found to contain 0.0381 moles of HI, 0.0471 moles of H2, and 0.0364 moles of I2 in a 1.00 L container. Is the reaction at equilibrium? And if not, what direction must it run in order to reach equilibrium?

a. The reaction is at equilibrium
b. The reaction must run towards the products to reach equilibrium
c. The reaction must run towards the reactants to reach equilibrium


Answer: c. The reaction must run towards the reactants to reach equilibrium

When she introduced 0.0683 moles of SO3 gas into a 1.00L container, she found the equilibrium concentration of O2 gas to be 0.0152 M. What is the value of the equilibrium constant, K?

A student ran the following reaction in the laboratory at 1090 K:

2SO3(g) 2SO2(g) + O2(g)

When she introduced 0.0683 moles of SO3 gas into a 1.00L container, she found the equilibrium concentration of O2 gas to be 0.0152 M. What is the value of the equilibrium constant, K?

a. 0.00498
b. 0.00978
c. 0.0122
d. 0.0125
e. 0.0152


Answer: b. 0.00978

An equilibrium mixture of the three gases in a 14.1 L container at 352K contains 0.121 moles of CH2Cl2, 0.661 moles of CH4, and 0.223 moles of CCl4. What is the value of the equilibrium constant at 352K?

Consider the following reaction: 2 CH2Cl2(g) CH4(g) + CCl4(g)

An equilibrium mixture of the three gases in a 14.1 L container at 352K contains 0.121 moles of CH2Cl2, 0.661 moles of CH4, and 0.223 moles of CCl4. What is the value of the equilibrium constant at 352K?

a. 0.0254
b. 0.0864
c. 0.0993
d. 10.1
e. 11.6


Answer: d. 10.1

The reaction: 2S(s) + 3O2(g) 2SO3(g) has an equilibrium constant of K = 1.91. What is the value of the equilibrium constant for the reaction: SO3(g) S(s) + 3/2 O2(g) ?

The reaction: 2S(s) + 3O2(g) 2SO3(g) has an equilibrium constant of K = 1.91. What is the value of the equilibrium constant for the reaction: SO3(g) S(s) + 3/2 O2(g) ?

a. 0.274
b. 0.524
c. 0.724
d. 1.38
e. 3.65


Answer: c. 0.724

For the reaction, N2O4(g) 2NO2(g), which of the following statements is true about this reaction at equilibrium?

For the reaction, N2O4(g) 2NO2(g), which of the following statements is true about this reaction at equilibrium?

a. The concentration of NO2 is equal to the concentration of N2O4
b. The rate of the dissociation of N2O4 is equal to the rate of formation of N2O4
c. The rate constant for the forward reaction is equal to the rate constant for the reverse reaction
d. The concentration of NO2 divided by the concentration of N2O4 is equal to a constant
e. Two of the above


Answer: b. The rate of the dissociation of N2O4 is equal to the rate of formation of N2O4