(Photo credit Ingy The Wingy)
Besides sharing Chemistry Tips and Exam Strategies, the other aim of this chemistry blogsite is to encourage students to learn the Chemistry Theories and Concepts in a more experiential and interesting way – HOW ? By relating chemistry theories to everyday life processes and experience.
Thermit Process came to my mind several days back when i was passing by the railway track in the west area of Singapore, and today i am going to share with you more on how Thermit Process – which is a highly exothermic reaction is used to weld together steel railway lines. It involves the reduction of iron (III) oxide to iron by aluminium.
Now, let’s check out a chemistry question that requires your concepts in several chemistry topics, namely:
- Energy Changes (Endothermic/Exothermic Reactions)
- Redox (Oxidation/Reduction)
- Mole Calculations
Question:
In the highly exothermic Thermit Process to weld railway lines, aluminium is used to reduce iron (III) oxide to iron based on the balanced chemical equation below:
2Al + Fe2O3 -> Al2O3 + 2Fe
(a) Indicate the state symbols for all the reactants and products involved
(b) Calculate what mass of aluminium is needed to react completely with
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Recently, i received several emails and comments from readers (students) to share more challenging Mole Calculations (or Mole Concepts) questions in this chemistry blog. So here we go………..
Question:
What would be the concentration of the hydrochloric acid produced if all the hydrogen chloride gas from the reaction between 50 g of pure sulfuric acid and an excess of sodium chloride was collected in water, and the solution made up to a volume of 400 cm3 of water?
Based on equation: NaCl(s) + H2SO4(aq) –> NaHSO4(s) + HCl(g)
Now, try it out and leave your suggested answer (and possibly your solution/steps) in the comment section below.
The best way to learn is NOT by reading or looking, instead it is by Taking Actions.
I look forward to seeing you answers. Cheers! Enjoy! =)
In the previous blogpost, we have discussed on the Common Errors on Calculating Empirical Formula, when given Composition by Mass. Today we shall go one step further and see how we can determine the Molecular Formula from an Empirical Formula.
The Molecular Formula shows all the atoms of each element contained in one molecule.
Empirical Formula shows the simplest ratio of the different types of elements present in a molecule.
For example, Hexane has Molecular Formula of C6H12 and Empirical Formula of CH2.
As such, Molecular Formula is a simple multiple of the Empirical Formula:
Molecular Formula = n X Empirical Formula
where n = 1, 2, 3, etc
The molecular formula can be calculated from:
- Empirical Formula
- Relative Molecular Mass, Mr of Compound
Let’s take a look at an example.
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