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.

Vancouver Chemistry Tutor

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, UBC CHEM 111/113, CHEM 121/123, CHEM 233, CHEM 205. LANGARA CHEM 1120, 1220, 2216, 2316 and 2416. I can teach with both English and Mandarin. Please call 604-808-6827.

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 --63

Welcome back to my blog. Following is Question 62 I posted earlier.

 

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

The correct answer is D. This a tough question to most students because I found a lot of students studying AP know little about predicting product of reactions. 

First of all , we need to figure out which one of them will react with dilute hydrochloric acid and generate a gas. Zn is an active metal and will react with dilute acid and produce hydrogen gas. For B, C, and D, they will undergo double replacement reactions with dilute HCl and produce a salt and another acid. Both HNO3 and HBr are strong acid and stay in aqueous solution. But H2CO3 is a weak acid and it decomposes to CO2 and water. 

Now we need to figure out which one of them H2 or CO2, is denser than air?

According to Avogadro's Law, at the same temperature and pressure, any gas has a same volume. While density is defined as mass per volume, the higher the molecular weight, the denser it is, since their molar volume is the same. Air has an average molecular weight of 29, H2 is 2 and CO2 is 44. Thus CO2 is denser than air, D is the correct answer.

Following is question 63 of the series:

63.  A 20.00 mL sample of a Ba(OH)2  solution is titrated with 0.245 M HCl. If 27.15 mL of HCl is required, what is the molarity of the Ba(OH)2  solution?
(A)  0.166 M
(B)  0.180 M

(C)  0.333 M
(D)  0.666 M

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.

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。