Dr. Zhang Chemistry Tutoring 张老师化学家教

Ph. D in Chemistry with years of experience offering chemistry tutoring on AP Chemistry, IB Chemistry, SAT Chemistry, Chemistry 11 and 12, University Level General Chemistry and second year Organic Chemistry including UBC CHEM 111, CHME 113, CHEM 121, CHEM123, CHEM 154, CHEM 203, CHEM 213, CHEM 233, CHEM 205, CHEM 235 and CHEM 245, Langara College CHEM 1114, CHEM 1118, CHEM 1120 and CHEM 1220. I can teach with both English and Mandarin. Please call 604-808-6827. 南开大学化学系博士，UBC化学系博士后，多年经验辅导AP化学，IB化学，SAT化学，十一年级和十二年级化学,大学一年级普通化学和二年级有机化学和物理化学，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。请电604-808-6827.

AP Chemistry Question of the Day --65

Long time no see. It has been a while  since I last wrote on my blog. The 2016 AP exam is done and I personally think this year the free response questions are easier than last year. I would expect a higher  percentage of 5 overall.
Here comes Question 65 of the series:

Q 65: Which of the following factors would affect vapour pressure:
I. Identity of the substance;
II. Temperature
III. Shape of the container
IV. Size of the container
A. I and II
B. I and III
C. I, II and III
D. all of them

The correct answer is A. Vapour pressure indicates a substance's tendency to evaporate. substance with higher intermolecular force tends to have lower vapour pressure. Also the vapour pressure is only dependent on the temperature for a given substance and size and shape of the container will not affect vapour pressure since it represents the ability of the substance to evaporate. Pressure itself is an intensive property.

Let me know if you have a particulate question regarding AP chemistry or any question regarding chemistry and I am more than happy to discuss with you.

UBC Chemistry Tutor

Experienced Ph. D. in chemistry offering tutoring service for UBC CHEM111. CHEM113, CHEM121, CHEM123, CHEM233, CHEM 235, CHEM 205, CHEM 203, CHEM 213, CHEM 235 and CHEM 245. Personalized tutoring tailored to individual needs. Guaranteed improvement and success.  
For your tutoring needs, please call Dr. Zhang at 604-808-6827. 

AP Chemistry Question of the Day --65

Welcome back to my blog. Since most schools are doing the unit on acid and base at this time of the year and here is another question related to this topic.

Question 65: Four acids HA, HB and HC and HD solutions have the same pH, which of the following statements is correct:
A. They all have the same concentration
B. They are all strong acids
C. They are all weak acid
D. not enough information to make any conclusion

The correct answer is D. pH represents the concentration of hydronium ion in solution. The pH if an acidic solution is dependent on both the Ka and the concentration of the acid. A solution of a strong acid can have a higher pH due to lower concentration and a solution of a weak acid cna have a lower pH due to higher concentration.

Hope this helpful.

Thank you for visiting my blog. If you have any comments or questions that you would like to be answered, please leave a massage and I will take care of it.

AP Chemistry Question of the Day --64

I have not written here for a long time. AP season is coming soon in a couple of months. I will resume my series and hopefully it is helpful to anyone who come across to visit this site. Instead of posting a question and answer it the next day, I am going to post the question and answer at the same time.

Question 64: Which one of the following cidic solutions requires the most 0.1000M NaOH aqueous solution to neutralize completely:
A. 0.1000M HCl 25ml
B. 0.1000M HF 25ml
C. 0.05000M H2SO4 25ml
D. 0.05000M H2CO3 25ml
E. They are all the same

The answer to this question is E. When an acid and a base react, whenever there is a strong acid or base involved, the reaction will go to completion. The amount of base required will be totally determined by the mole number of the protons in the acid. It does not matter the acid is strong or weak, monoprtotic or diprotic. It is the number of moles of H+ that is in the acid that determines how much base will be needed to completely neutralize.

Hope this helps with your understanding on acid and base and thank you for visiting my blog.