Adrian Dingle’s Chemistry Pages - The Blog

Two, extra TOPIC 4 questions for my AP classes

Take a look at these BEFORE the test on Wed 10/1.

Question 1: It concerns silicon tetrachloride and can be found as part (b) on this page; http://www.drbateman.net/asa2sums/sum1.2/test1.2.htm

A few notes about this question;

• 1cm³ = 1mL
• 1dm³ = 1L
• the equation for “neutralisation” that the questions refers to is;

HCl + NaOH ==> NaCl + H₂O

• The correct answer is 91.8%

Question 2: This question has been adapted from an unkown source;

2.00 g of an impure copper ore that contains some undetermined amount of copper pyrites with the formula CuFeS₂, is treated so that all of the copper ions are dissolved into exactly 100mL of solution. 20mL portions of this solution are treatd with excess KI and the reaction below takes place;

2Cu²⁺ + 4I^- ==> 2CuI + I₂

The iodine that is produced in this reaction requires 18.3mL of 0.10M sodium thiosulfate to react completely according to the equation below;

2S₂O₃^2- + I₂ ==> S₄O₆^2- + 2I^-

Calculate the % purity of the ore.

• The correct answer is 84%

Subscriber Updates

AP Worked Answer 1999, 2 has been updated in the relevant subscriber areas.

Subscriber Updates

A small typo has been corrected on the AP TOPIC 3 notes. The Rydberg equation has been amended to read 10^-18 from 10^18.

Subscriber Updates

REGULAR Worksheets 3b and 3c have been added to relevant subscriber areas.

I am always right, you are always wrong!

As an Englishman who is living and teaching in the USA, I am still (even after over eight years here) treated as somewhat of a novelty by my students and the greater native population. Of course, it is true that I am a FIERCE defender of my nationality in ALL situations, circumstances and regards, but one particular area remains a pet peeve of mine - language.

Firstly I have worked both hard and consciously to keep my English (NOT British BTW), accent. Given I am in the Deep South of the USA I figured that it was imperative! Secondly the kids always marvel at the pronunciation and spelling of lots of things, but given my profession, especially the word Aluminium [sic]. I simply tell them that since we are speaking English, and that I am English and they are NOT, in that all matters relating to language and spelling I am right and they are wrong - that usually ends the conversation and it has a rather attractive logic (at least for me)!

Well, I hear you ask, why mention this now? Well I happened across the following small piece by Rod Beavon who is the Chief/Principal Examiner for Edexcel A Level Chemistry. Please take a moment to read it; it makes for an interesting two minutes.

http://www.rod.beavon.clara.net/sulphur.htm