AP Chemistry Question of the Day --48

Welcome back to my blog. Here comes the answer to question 46 I posted earlier. The correct answer is C. 

Oxygen, silicon are the top two abundant element on earth. Aluminum is the most abundant metal on earth and nitrogen is the most abundant element in the atmosphere. 

Following is Question 48 of the series. 

46. Electrons residing in which of the following orbitals  in a sodium atom experience the highest effective nuclear charge?

A. 1p

B. 2p

C. 2s

D. 3s

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

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AP Chemistry Question of the Day --47

Welcome back to my blog. Here comes the answer to question 46 I posted earlier. The correct answer is D. 

Electron affinity is the energy change accompanying the addition of an electron to a gaseous atom. Both F hand Cl have high electron affinity. However, the addition of electron will be introduced to the 2nd shell for F and 3rd shell for Cl. There is more space in the 3rd shell of Cl to release the repulsions among electrons, while in the 2nd shell of fluorine, the repulsions make it less favourable. The overall effect is that Cl has higher electron affinity than F.

Electronegativity is referring to the ability of the atom to pull the shared electrons towards itself in a covalent bond. F has the highest electronegativity.

Following is Question 47 of the series. 

46. Which elements is most abundant on earth?

A. Al

B. Si

C. O

D. N

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

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AP Chemistry Question of the Day --46

Welcome back to my blog. Here comes the answer to question 44 I posted earlier. The correct answer is B. 

When two atoms of the same element form a bond, they equally share the bonding electrons and the bond is  non polar  and the molecule is non polar, for example hydrogen in answer A. When two atoms of different elements form a bond, they do not share the bonding electron pair equally. The atom with higher electronegativity pulls the bonding electron pair closer to itself, making it partially negative and the other atom partially positive. As a result, the bond is polar.

The polarity of a molecule depends on both the polarity of the individual bond and the geometry of the molecule. If the geometry of the molecule is arranged in a way that all the dipole moments of the polar bond can cancel out, the overall molecule will appear to be non polar.

CO2 has two polar bonds, but the two dipole moments are opposite in direction and thus cancel out each other. The molecule is non polar.

Both answer C and D has outstanding dipole moments when molecular geometry has been taken into account. They are polar molecules.

Following is Question 46 of the series. 

46. Which elements have the highest electron affinity and electronegativity respectively?

A. F, F

B. F, Cl

C. Cl, Cl

D. Cl, F

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

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AP Chemistry Question of the Day --45

Welcome back to my blog. Here comes the answer to question 44 I posted earlier. The correct answer is E. 

When equilibrium is reached, it is dynamic. The rate of the forward reaction is equal to the rate of the backward reaction and the concentration of all the components remain constant.

As a result, at equilibrium the concentrations of R, Q and P are constant, but may not be equal. The rate of the forward reaction is equal to the rate of the backward reaction for both step one and step 2, but the  rates for step 1 and 2 might be different.

Following is Question 45 of the series. 

45. Which of the following is a non polar molecular that contains polar bonds?

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

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AP Chemistry Question of the Day --44

Welcome back to my blog. Here comes the answer to question 43 I posted earlier. The correct answer is C. 

The potential energy of the products are higher than that of the reactants. The forward reaction is endothermic. When temperature is increased, the forward reaction is favoured and the equilibrium shifts to the right.

Activation energy for any reaction is positive. It is defined as the minimum energy required for a effective collision to happen. A is not correct.

Starting with reactants only, the forward reaction rate will decrease with the decrease in reactant concentration and the backward reaction rate will increase with the concentrate of the product increasing. When both rate are equal, the reaction reaches equilibrium. B is not right.

The potential energy of the products are higher than that of the reactants. The activation energy for the forward reaction is higher than that of the reverse reaction. D is not right.

The potential energy of the products are higher than that of the reactants. The forward reaction is endothermic. The enthalpy change for the forward reaction is positive. E is incorrect.

Following is Question 44 of the series. 

44. Suppose that conversion of reactant R to product P involves the following sequence of reversible reactions. When the system reaches a state of dynamic equilibrium, which of the following statements is true? 

A The rate of step R → Q is equal to the rate of step Q → P. 
B [R] = [Q] = [P] 
C [Q] = [P] / [R] 
D The rate of step Q → R is equal to the rate of step Q → P. 
E The rate of step R → Q is equal to the rate of step Q → R. 

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

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AP Chemistry Question of the Day --43

Welcome back to my blog. Here comes the answer to question 42 I posted earlier. The correct answer is D. 

Ionic compounds are mostly formed between a metal and a non metal. The only exception is ammonium salt where NH4 is a polyatomic ion. It has covalent bond inside the ammonium ion and the bond between ammonium and the anion is ionic.
D is the only compound that is not ionic.

Following is Question 43 of the series. 

43. Consider the following energy level diagram for a reaction that occurs in a single step. Which of the following statements is true? 

A The activation energy for the reverse reaction is less than zero. 
B Starting from reactants only, and before equilibrium is established, the rate of the forward reaction continually increases. 
C The effect of a temperature change on the rate is greater for the forward reaction than for the reverse reaction. 
D The activation energy for the forward reaction is less than that of the reverse reaction. 
E The enthalpy change for the forward reaction is less than zero. 

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

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AP Chemistry Question of the Day --42

Welcome back to my blog. Sorry for the delay updating my blog. My computer had some problems. Here comes the answer to question 41 I posted earlier. The correct answer is A. 

Since the system is assumed thermally insulated from the surroundings, according to the First Law of Thermodynamics, energy can not be produced or consumed and only can  be transferred. The heat water absorbed should be equal to the heat the metal lost.

Following is Question 42 of the series. 

42. Which of the following is not an ionic compound? 

A ammonium fluoride, NH4F 
B sodium hydroxide, NaOH 
C lithium nitrate, LiNO3 
D oxygen difluoride, OF2 
E potassium hydride, KH 

I will post the answer and explanation tomorrow. 

Thank you very much for reading my post, I am available to discuss any topics in AP chemistry. Please give me a call at 604-808-6827 or email me at vancouverchemistrytutor@gmail.com. My website is located at www.vancouverchemistrytutor.com.

Regards!