# 14.1 Types of reactions  (Page 4/4)

 Page 4 / 4
Sodium metal is very reactive. Sodium metal reacts vigourously with water and should never be placed in water. Be very careful when handling sodium metal.

## Aim:

To use experiments to determine what type of reaction occurs.

## Apparatus:

Soluble salts (e.g. potassium nitrate, ammonium chloride, sodium carbonate, silver nitrate, sodium bromide); hydrochloric acid ( $\mathrm{HCl}$ ); sodium hydroxide( $\mathrm{NaOH}$ ); bromothymol blue; zinc metal; copper (II) sulphate; beakers; test-tubes

## Method:

• For each of the salts, dissolve a small amount in water and observe what happens.
• Try dissolving pairs of salts (e.g. potassium nitrate and sodium carbonate) in water and observe what happens.
• Dissolve some sodium carbonate in hydrochloric acid and observe what happens.
• Carefully measure out $20{\mathrm{cm}}^{3}$ of sodium hydroxide into a beaker.
• Add some bromothymol blue to the sodium hydroxide
• Carefully add a few drops of hydrochloric acid to the sodium hydroxide and swirl. Repeat until you notice the colour change.
• Place the zinc metal into the copper sulphate solution and observe what happens.

## Results:

Answer the following questions:
• What did you observe when you dissolved each of the salts in water?
• What did you observe when you dissolved pairs of salts in the water?
• What did you observe when you dissolved sodium carbonate in hydrochloric acid?
• Why do you think we used bromothymol blue when mixing the hydrochloric acid and the sodium hydroxide? Think about the kind of reaction that occurred.
• What did you observe when you placed the zinc metal into the copper sulphate?
• Classify each reaction as either precipitation, gas forming, acid-base or redox.
• What makes each reaction happen (i.e. what is the driving force)? Is it the formation of a precipitate or something else?
• What criteria would you use to determine what kind of reaction occurs?
• Try to write balanced chemical equations for each reaction

## Conclusion:

We can see how we can classify reactions by performing experiments.

In the experiment above, you should have seen how each reaction type differs from the others. For example, a gas forming reaction leads to bubbles in the solution, a precipitation reaction leads to a precipitate forming, an acid-base reaction can be seen by adding a suitable indicator and a redox reaction can be seen by one metal disappearing and a deposit forming in the solution.

## Summary

• The polar nature of water means that ionic compounds dissociate easily in aqueous solution into their component ions.
• Ions in solution play a number of roles. In the human body for example, ions help to regulate the internal environment (e.g. controlling muscle function, regulating blood pH). Ions in solution also determine water hardness and pH.
• Water hardness is a measure of the mineral content of water. Hard water has a high mineral concentration and generally also a high concentration of metal ions e.g. calcium and magnesium. The opposite is true for soft water.
• Conductivity is a measure of a solution's ability to conduct an electric current.
• An electrolyte is a substance that contains free ions and is therefore able to conduct an electric current. Electrolytes can be divided into strong and weak electrolytes, based on the extent to which the substance ionises in solution.
• A non-electrolyte cannot conduct an electric current because it dooes not contain free ions.
• The type of substance , the concentration of ions and the temperature of the solution affect its conductivity.
• There are three main types of reactions that occur in aqueous solutions. These are precipitation reactions, acid-base reactions and redox reactions.
• Precipitation and acid-base reactions are sometimes known as ion exchange reactions. Ion exchange reactions also include gas forming reactions.
• A precipitate is formed when ions in solution react with each other to form an insoluble product. Solubility 'rules' help to identify the precipitate that has been formed.
• A number of tests can be used to identify whether certain anions are present in a solution.
• An acid-base reaction is one in which an acid reacts with a base to form a salt and water.
• A redox reaction is one in which electrons are transferred from one substance to another.

## End of chapter exercises

1. Give one word for each of the following descriptions:
1. the change in phase of water from a gas to a liquid
2. a charged atom
3. a term used to describe the mineral content of water
4. a gas that forms sulphuric acid when it reacts with water
2. Match the information in column A with the information in column B by writing only the letter (A to I) next to the question number (1 to 7)
 Column A Column B 1. A polar molecule A. ${\mathrm{H}}_{2}{\mathrm{SO}}_{4}$ 2. molecular solution B. ${\mathrm{CaCO}}_{3}$ 3. Mineral that increases water hardness C. $\mathrm{NaOH}$ 4. Substance that increases the hydrogen ion concentration D. salt water 5. A strong electrolyte E. calcium 6. A white precipitate F. carbon dioxide 7. A non-conductor of electricity G. potassium nitrate H. sugar water I. ${\mathrm{O}}_{2}$
3. For each of the following questions, choose the one correct answer from the list provided.
1. Which one of the following substances does not conduct electricity in the solid phase but is an electrical conductor when molten?
1. $\mathrm{Cu}$
2. ${\mathrm{PbBr}}_{2}$
3. ${\mathrm{H}}_{2}\mathrm{O}$
4. ${\mathrm{I}}_{2}$
(IEB Paper 2, 2003)
2. The following substances are dissolved in water. Which one of the solutions is basic?
1. sodium nitrate
2. calcium sulphate
3. ammonium chloride
4. potassium carbonate
(IEB Paper 2, 2005)
4. Explain the difference between a weak electrolyte and a strong electrolyte. Give a generalised equation for each.
5. What factors affect the conductivity of water? How do each of these affect the conductivity?
6. For each of the following substances state whether they are molecular or ionic. If they are ionic, give a balanced reaction for the dissociation in water.
1. Methane ( ${\mathrm{CH}}_{4}$ )
2. potassium bromide
3. carbon dioxide
4. hexane ( ${\mathrm{C}}_{6}{\mathrm{H}}_{14}$ )
5. lithium fluoride ( $\mathrm{LiF}$ )
6. magnesium chloride
Click here for the solution
7. Three test tubes (X, Y and Z) each contain a solution of an unknown potassium salt. The following observations were made during a practical investigation to identify the solutions in the test tubes: A: A white precipitate formed when silver nitrate ( ${\mathrm{AgNO}}_{3}$ ) was added to test tube Z. B: A white precipitate formed in test tubes X and Y when barium chloride ( ${\mathrm{BaCl}}_{2}$ ) was added. C: The precipitate in test tube X dissolved in hydrochloric acid ( $\mathrm{HCl}$ ) and a gas was released. D: The precipitate in test tube Y was insoluble in hydrochloric acid.
1. Use the above information to identify the solutions in each of the test tubes X, Y and Z.
2. Write a chemical equation for the reaction that took place in test tube X before hydrochloric acid was added.
(DoE Exemplar Paper 2 2007)

#### Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
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Alexandre
what is the stm
Brian Reply
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Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
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The fundamental frequency of a sonometer wire streached by a load of relative density 's'are n¹ and n² when the load is in air and completly immersed in water respectively then the lation n²/na is
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Properties of longitudinal waves
Sharoon Reply

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Source:  OpenStax, Siyavula textbooks: grade 10 physical science [caps]. OpenStax CNX. Sep 30, 2011 Download for free at http://cnx.org/content/col11305/1.7
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