Langara Chemistry Tutor

 Experienced Ph. D. in chemistry offering tutoring service for CHEM 1114, 1118, 1120 and 1220. Personalized tutoring tailored to individual needs. Guaranteed improvement and success.  I can teach with both English and Chinese. For your tutoring needs, please call Dr. Zhang  at 604-808-6827.

南开大学化学博士，UBC化学系博士后多年经验辅导CHEM 1114, 1118, 1120, 1220 . 因材施教，帮你理解重点，抓住要点，取得满意考试成绩。可用中英文双语沟通。

如果您有辅导需求，请随时与我联系 604-808-6827。

Vancouver Chemistry Tutor 张老师化学家教

南开大学化学博士，UBC化学系博士后多年经验辅导AP化学，IB化学， SATII化学，十一年级和十二年级化学， 因材施教，帮你理解重点，抓住要点，取得满意考试成绩。可用中英文双语沟通。

 如果您有一对一辅导需求，请随时与我联系 604-808-6827。

AP Chemistry Question of the Day --49

Welcome back to my blog. Here comes the answer to question 48 I posted earlier. The correct answer is C. 

Inner electrons shield outer electrons more efficiently. As a result, the lower the principle quantum number, the closer the electron is to the nucleus,  the less screening the electron feels and the higher the effective nuclear charge. Among the four choices, C is correct. 1p orbital does not exist. comparing 2s and 2p, 2s has lower energy than 2p.


Following is Question 49 of the series. 

49. What is the solubility of lead (II) bromide at 298K if Ksp of lead (II) bromide is 6.6x10-6?

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!

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.

Regards!

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.

Regards!

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.

Regards!

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.

Regards!