恭喜S同学SATII化学考满分

今天早晨刚起床，习惯性的看看手机上有没有新的短信和电邮，收到S同学发给我的短信， “SAT chem 800". 顿时清醒了很多，可爱的孩子向我报喜了。SAT 化学考试满分800分，S同学得了满分。我为他骄傲。
SAT化学是美国考试中心college board为设立的化学学科的标准化测试，为时一小时，共64道选择题和17道是非判断题，涵盖的范围主要是高中十一年级和十二年级的化学，对化学概念的掌握要求很高。同时对答题的速度有一定要求。
如果您有意参加SAT化学考试，请与我联系，向800分努力。
我的电话是604-808-6827

AP Chemistry Question of the Day --57

Welcome back to my blog. Here is question 56 I posted earlier:

The correct answer is B. From the potential diagram, it can be concluded that the products have lower potential energy than the reactants and the reaction is exothermic. According to La Chatellier's Principle, the equilibrium will shift to endothermic side when temperature is increased. The endothermic direction is the reverse of the above direction. Since equilibrium shifts to left, the K will decrease.

Following is question 57 of the series:
57.

I will post the answer in my next blog.

Thank you very much for reading my post, I am available to discuss any topics in 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!

Congratulations to my hard working students

I am so happy today that I heard back from my three students who sat the June 8th SAT II Chemistry exam got  scores of 800, 770 and 740. All of them were first time takers of the exam. Good job! I am so proud of you.

AP Chemistry Question of the Day --56

Welcome back to my blog. Here is question 55 I posted earlier. 
55. Aqueous solutions of AgNO3, Cu(NO3)2 and Cr(NO3)3 are electrolyzed using the same quantity of electricity. How do the number of moles of metal formed compare?

A.      Ag = Cu = Cr

B.      Ag > Cu > Cr

C.      Ag < Cu < Cr

D.      Cu > Ag > Cr

The correct answer is B. To answer this question, we need to understand how electrolysis works. In an aqueous electrolytic cell, redox reaction happens so that the cation of the salt or hydrogen ion from water is reduced to its elemental form and the anion or hydroxide from water is oxidized to its oxidation product or oxygen. Whether water will be involved depends on the reduction potentials of the cation and the anion. If the anion has a lower reduction potential than hydroxide, then its oxidation is dominant. If the cation has a higher reduction potential than hydrogen, its reduction is then dominant. Also we need to take into account of the pH and over potential effect of water. In this question, since all of the metal ions have higher reduction potential than hydrogen, they are going to be reduced. As diver ion, cooper ion and chromium ion has a charge of +1, +2 and +3 respectively, to get one mole of metal reduced, they will need 1, 2 and 3 moles of electrons respectively. If the same amount of electricity is consumed, then the mole number of the metals would be: 1mole Ag:0.5mole Cu:0.33mole chromium. Thus, B is the correct answer.

Following is question 56 of the series:

56. 

I will post the answer in my next blog.

Thank you very much for reading my post, I am available to discuss any topics in 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化学小班辅导

跃跃欲试要参加明年的AP化学考试吗？ AP考试的成绩不仅可以证明你的学习能力，而且可以帮助你免修部分大学课程，给你更多的时间去学习更多的东西。 AP成绩是5分制，5分是大家努力的目标。
我多年辅导AP化学，熟识去年刚刚推出的新的考试大纲，备有大量复习资料，因材施教，深入浅出，中英文结合，帮你理解要点，抓住重点，取得满意成绩。
我计划九月份推出两个AP化学辅导小班，每班限最多四名同学：
2014年9月20日起，每周六下午2点到4点
2014年9月21日起，每周日下午2点到4点
名额有限，请尽快致电张老师604-808-6827，或电邮vancouverchemistrytutor@gmail.com报名
张老师的个人博客： http://vancouverchemistry.blogspot.ca
张老师的网页： www.vancouverchemistrytutor.com
一对一单独辅导，请随时和张老师联系。

AP Chemistry Question of the Day --55

Welcome back to my  blog. Here is question 54 I posted yesterday. The correct answer is B.

There are several factors affecting reaction rate such as temperature, concentration, surface area and catalyst. But here what is being tested is the collision theory.
For a chemical reaction to happen, the reactant molecules have to collide with enough energy and proper orientation. If the reactants molecules are easier to bump into each other, the reaction should occur relatively faster. As a result, from the four choices above, B is the correct answer. A and D are reactions in gas phase. Gas molecules are far apart and are not likely to collide as easily as in solution. C is a heterogeneous reaction. Again the reaction is limited at the surface of the lead.

Following is Question 55 of the series,

55. Aqueous solutions of AgNO3, Cu(NO3)2 and Cr(NO3)3 are electrolyzed using the same quantity of electricity. How do the number of moles of metal formed compare?

A.      Ag = Cu = Cr

B.      Ag > Cu > Cr

C.      Ag < Cu < Cr

D.      Cu > Ag > Cr

I will post the answer in my next blog.

Thank you very much for reading my post, I am available to discuss any topics in 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 --54

Welcome back to my blog. Following is Question 53 I posted earlier. The correct answer is E.

53.  A solution appears yellow.  It must be absorbing in the  

    (a) yellow only    (b) red only    (c) green only    (d) blue only   (e) purple only.

I am always surprised when my students are confused with colours. As we know, the sunlight consists of UV, visible and infrared lights. The visible region is white (or colourless) when combined. It is actually a mixture of all the colours of the rainbow: red, orange, yellow, green, blue and purple. If a subject appears to be white, then it absorbs no visible light and reflects all the colours. If a subject appears to be black, then it absorbs all the colours of the visible region. If a subject appears a particular colour, for example yellow as stated in the above question, then it reflects only yellow light and absorbs the rest of the colours. The colour that was absorbed should be complimentary to yellow, which means when combined with yellow, it will be black. What colour is absorbed then:
There are three primary colours: red, yellow and blue, as shown below:

If only yellow light was reflected, then red and blue was absorbed and the combination of red and blue is purple. As a result, purple light was absorbed.

Following is question 54 of the series:














I will post the answer in my next blog.

Thank you very much for reading my post, I am available to discuss any topics in 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!