化学家教 Chemistry Tutor

化学家教多年经验专业辅导各个级别的化学课程，包括十年级科学，十一年级和十二年级化学，AP化学， IB化学，SAT化学UBC和LANGARA大学一年级普通化学和大学二年级有机化学，物理化学和分析化学。张老师从南开大学化学系博士毕业，在UBC化学系工作8年，具有牢固的化学知识基础和丰富的实际工作经验，如果您有家教需要，请和张老师联系，电话：604-808-6827， 电邮：vancouverchemistrytutor@gmail.com

张老师化学家教

首先祝贺张老师的同学们在五月份的AP化学和六月份SAT化学考试中取得了好成绩。
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， 大学一年级普通化学，大学二年级有机化学和物理化学，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。请电604-808-6827与张老师联系。
张老师的个人网页：www.vancouverchemistrytutor.com
张老师的博客：http://vancouverchemistry.blogspot.ca

AP Chemistry Question of the Day --62

Welcome back to my blog. Following is Question 61 I posted earlier.

 61. In an experiment to determine the percentage of water in a solid hydrate by heating, what is the
best indication that all the water has been removed?
(A)  The solid melts.
(B)  The solid changes color.
(C)  Water vapor no longer appears.
(D)  Successive weighings give the same mass.

The correct answer is D. The water in a  hydrate can be removed by heating. As the water is removed, the mass of the sample will decrease. If successive weighings give the same mass, this means all the water has gone. Depending on what size of your sample is, you may not be able to observe water vapour. As a result, C is not correct even though it looks reasonable. Some of the solid will change colour while some do not, B is not always true. A is not correct because it is not related to water removing. When the solid melt, it is at its melting point and that is all you know. 

Following is question 62 of the series:

 62. Which solid reacts with dilute hydrochloric acid at 25 °C to produce a gas that is more dense than air?

Thank you very much for reading my blog. I am available to discuss any questions regarding all levels of chemistry. Please give me a call at 604-808-6827 if you need any assistance.

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!

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。