100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Grade 12 Physical Sciences chemistry revision R50,00   Add to cart

Exam (elaborations)

Grade 12 Physical Sciences chemistry revision

 10 views  0 purchase

has questions and answers on chemistry side of physics physics side is on the next document on my profile

Preview 4 out of 35  pages

  • April 19, 2024
  • 35
  • 2023/2024
  • Exam (elaborations)
  • Questions & answers
All documents for this subject (637)
avatar-seller
BookSquad
,
, lOMoARcPSD|23479258




Saturday X-tra X-Sheet: 2

Revision of Grade 11 Chemical Change
Key Concepts

This lesson focuses on the following:

• Representation of chemical change
• Writing down chemical formulae of both reactants and products
• Role of kinetic energy in chemical reactions
• The collusion theory
• Energy changes during chemical reactions and graphs
• Types of chemical reactions

Terminology & definitions

• Collision theory – molecules and atoms must have enough kinetic energy and the
right orientation to react chemically
• Reactants – chemical entities in the form of atoms or molecules that interact
together to form a product
• Products – chemical substances formed when a chemical reaction takes place
• Exothermic reaction – a chemical reaction that liberates/gives off energy
• Endothermic reaction – a chemical reaction that takes in energy
• Heat of reaction ( H) – the energy difference between products and reactants
• Activation energy – energy needed to start a chemical reaction
• Catalyst – a substance that speeds up a chemical reaction. It does so by lowering
the energy hill (amount of activation energy needed to initiate a chemical reaction).
• Activated complex – a state during a chemical reaction where the reactants have
enough energy to be able to react with each other.

X-planation of key concepts and terminologies

Chemical change is represented by a chemical equation. When sodium reacts with
oxygen to form sodium oxide, the following equation is used to represent the chemical
change that occurrs from the reactants to the formation of products:
sodium + oxygen sodium oxide.
This chemical equation can be written in symbol form:
Na(s) + O2(g) Na2O(s).
It is important to show the states (phases) in which the reactants and products occur.
(s) for solid, (g) for gas, ( ) for liquid and (aq) for substance reacting in the form of
solutions where water is the solvent.

Whilst it may be easier to understand where the chemical formulae for the reactants
come from; that sodium is represented as Na on the periodic table and that oxygen is
represented as O and that it exists as a diatomic molecule, hence the O2, it is often
difficult to tell what the chemical formula of the product is going to be. In this case the
chemical formula of the product is Na2O. Let’s look at where this comes from: Ions
formed from atoms of elements in group1 will always carry a charge of 1+. Thus
sodium ion will be represented as Na1+ or Na+. On the other hand, ions of non metals


1

Downloaded by Athi (athidikana@gmail.com)

, lOMoARcPSD|23479258




from group 6 will carry a negative charge given by 6 – 8 = - 2. Thus the charge on an
oxygen ion will be O2-. The numerical values of the charges carried by the ions are
used to tell the resulting chemical formula. This is done by swapping these numerical
values between the reacting ions and placing them as subscripts on the product
molecule formed. Thus for sodium Oxide, the chemical formula becomes, Na2O as
shown above.

Example 1:
Write the balanced chemical equation for the reaction of aluminium and chlorine to
produce aluminium chloride.

Solution:
Step 1: The chemical equation in words is:
Aluminium + Chlorine Aluminium Chloride.

Step 2: Write the formula of all reactants and products
Aluminium: Al
Chlorine: Cl2 (Remember: Chlorine is diatomic_
Aluminium chloride: AlCl3

Aluminium is a metal found in group 3 in the periodic table and will loose three
electrons and so the charge on Aluminium will be 3+. Chlorine comes from group 7, its
charge in the ion form will be 7 – 8 = -1. Thus the chloride ion will be C 1-. When the
numerical values of the two ions are swapped to find the resulting chemical formula of
the product, the following is found to be the chemical formula of Aluminium Chloride;
AlC 3.

Step 3: Write the chemical equation in symbols:

A (s) + C 2(g) A C 3(s).

Step 4: Balance the equation
2 A (s) + 3 C 2(g) 2A C 3(s).

Example 2
Write down the chemical formulae for:
(a) cobalt (II) chloride
(b) iron (III) oxide
(c) magnesium oxide
(d) ammonium nitrate
(e) ammonium sulphate
(f) calcium hydroxide

Example 3
Write down the balanced chemical equation for the reaction when zinc reacts with
hydrochloric acid to produce zinc chloride and hydrogen gas.




2

Downloaded by Athi (athidikana@gmail.com)

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

Quick and easy check-out

You can quickly pay through EFT, credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying this summary from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller BookSquad. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy this summary for R50,00. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

67232 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy summaries for 14 years now

Start selling
R50,00
  • (0)
  Buy now