In yesterday’s post on “O Levels Chemistry Tips Blog Marathon – Day 1”, i have given you the links to all the O Levels Chemistry Exam-Based Questions that we have discussed in this Chemistry Blogsite for Year 2008 as well as Year 2009. These includes Chemistry Tips and Exam Strategies on the tougher topics in O Levels Chemistry, with numerous participative discussions by readers of this blog.
Let’s continue Day 2 of this O Levels Chemistry Tips Blog Marathon with more O Levels Chemistry Exam-based questions, in order to prepare students for the Mid-Year Examinations
We shall start with a basic but “BIG” topic known collectively as “ACIDS, BASES & SALTS“. Many students hate dislike these chapters because they are very content based (i.e. lots of chemical and physical properties they need to know) and they are lost unsure what is required for them to know in order to score well for O Levels Examinations.
Just like going for soccer competition, the team (and players) would need to know the rules of the game first. As such, it is important that students know the learning objectives (aka what can be tested).
Learning outcomes for Acids, Bases & Salts are:
(Source: http://www.seab.gov.sg/SEAB/oLevel/syllabus/school/2009_GCE_O.html )
Acids and bases
(a) describe the meanings of the terms acid and alkali in terms of the ions they produce in aqueous solution and their effects on Universal Indicator
(b) describe how to test hydrogen ion concentration and hence relative acidity using Universal Indicator and the pH scale
(c) describe qualitatively the difference between strong and weak acids in terms of the extent of ionisation
(d) describe the characteristic properties of acids as in reactions with metals, bases and carbonates
(e) state the uses of sulfuric acid in the manufacture of detergents and fertilisers; and as a battery acid
(f) describe the reaction between hydrogen ions and hydroxide ions to produce water
(g) describe the importance of controlling the pH in soils and how excess acidity can be treated using calcium hydroxide
(h) describe the characteristic properties of bases in reactions with acids and with ammonium salts
(i) classify oxides as acidic, basic, amphoteric or neutral based on metallic / non-metallic character
(j) classify sulfur dioxide as an acidic oxide and state its uses as a bleach, in the manufacture of wood pulp for paper and as a food preservative (by killing bacteria)
Salts
(a) describe the techniques used in the preparation, separation and purification of salts (methods for preparation should include precipitation and titration together with reactions of acids with metals, insoluble bases and insoluble carbonates)
(b) describe the general rules of solubility for common salts to include nitrates, chlorides (including silver and lead), sulfates (including barium, calcium and lead), carbonates, hydroxides, Group I cations and ammonium salts
(c) suggest a method of preparing a given salt from suitable starting materials, given appropriate
information
Let’s check out some O Levels Chemistry-based questions:
Question 1: Based on topic “Acids, Bases & Salts”
Which of the following oxides reacts with an acid to form a salt but does NOT react with an alkali?
A. Aluminium oxide
B. Carbon dioxide
C. Copper (II) oxide
D. Zinc oxide
and
Question 2: Based on topic “Acids, Bases & Salts”
Titrating dilute sulfuric acid with aqueous potassium carbonate can be used to prepare potassium sulfate. Which conclusion can be drawn from this information?
A. Potassium carbonate is insoluble in water
B. Potassium carbonate neutralises sulfuric acid
C. Potassium sulfate is a base
D. Potassium sulfate is insoluble in water
>> Try out the questions and leave your Answers & Reasonings in the “Leave A Reply” section directly below.
The best way of learning is Experiential Learning, which requires 100% Participation! If you want to learn effectively and efficiently, the only way is to participate and not fear “failure” getting answers wrong.
It is only when you see your misconceptions and common errors made, that you can be aware of the common pitfalls, and avoid it in future. This is also how “Up Your Chemistry Grades Now!” chemistry guidebook is all about.
PS: We will come in to give our suggested answers and thought-process very shortly.
PPS: Leave your comments below. I would love to hear from you.
(1)c (2)b
can sum one plz explain to me da precipation method for preparingg salt
Question 1:
The answer is C, Copper (II) oxide because it is a base. A base only reacts with acids to form salt and water but does not react with alkalis. Aluminium oxide and Zinc oxide are amphoteric oxides so they react with both acids and alkalis to form salt and water. Carbon dioxide is an acidic oxide, so it only reacts with alkalis but not acids. Thus, only Copper (II) oxide reacts with an acid to form a salt but does not react with an alkali.
Question 2:
The answer is B, Potassium carbonate neutralises sulfuric acid. When aqueous potassium carbonate is added to sulfuric acid, neutralisation takes place and a salt, potassium sulfate is formed. A salt is formed only during neutralisation.
Sir, are my answers correct?
the answer is “c” because aluminium oxide will not react beacus of the layer of oxygen above aluminium.
carbon dioxide is an acidic oxide so it definitely will react with alkali.zinc oxide
will react with both acids and alkalis since it is an amphoteric oxide.so the only option left
is “c”.
the answer of question 2 is “b” because the rest are wrong options because potassium
carbonate and potassium sulphte are slouble salts and potassium sulphate is not
a base,it is a salt.
a) Acids give hydrogen ions when dissolved in water while alkalis give hydroxide ions when dissolved in water. acids turn universal indicator from green to red. while alkalis turn universal indicators from green to blue.
Sir should I answer in the same prose or any other suggested answer?