# Acid-base reactions  (Page 5/5)

 Page 5 / 5

Method:

1. Pour limewater into one of the test tubes and seal with a rubber stopper.
2. Carefully pour a small amount of hydrochloric acid into the remaining test tube.
3. Add a small amount of sodium carbonate to the acid and seal the test tube with the rubber stopper.
4. Connect the two test tubes with a delivery tube.
5. Observe what happens to the colour of the limewater.
6. Repeat the above steps, this time using sulfuric acid and calcium carbonate.

Observations:

The clear lime water turns milky meaning that carbon dioxide has been produced.

When an acid reacts with a carbonate a salt, carbon dioxide and water are formed. Look at the following examples:

• Nitric acid reacts with sodium carbonate to form sodium nitrate, carbon dioxide and water. $2{\mathrm{HNO}}_{3}+{\mathrm{Na}}_{2}{\mathrm{CO}}_{3}\to 2{\mathrm{NaNO}}_{3}+{\mathrm{CO}}_{2}+{\mathrm{H}}_{2}\mathrm{O}$
• Sulfuric acid reacts with calcium carbonate to form calcium sulfate, carbon dioxide and water. ${\mathrm{H}}_{2}{\mathrm{SO}}_{4}+{\mathrm{CaCO}}_{3}\to {\mathrm{CaSO}}_{4}+{\mathrm{CO}}_{2}+{\mathrm{H}}_{2}\mathrm{O}$
• Hydrochloric acid reacts with calcium carbonate to form calcium chloride, carbon dioxide and water. $2\mathrm{HCl}+{\mathrm{CaCO}}_{3}\to {\mathrm{CaCl}}_{2}+{\mathrm{CO}}_{2}+{\mathrm{H}}_{2}\mathrm{O}$

## Acids and bases

1. The compound NaHCO ${}_{3}$ is commonly known as baking soda. A recipe requires 1.6 g of baking soda, mixed with other ingredients, to bake a cake.
1. Calculate the number of moles of NaHCO ${}_{3}$ used to bake the cake.
2. How many atoms of oxygen are there in the 1.6 g of baking soda? During the baking process, baking soda reacts with an acid to produce carbon dioxide and water, as shown by the reaction equation below: ${\mathrm{HCO}}_{3}^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}^{+}\left(\mathrm{aq}\right)\to {\mathrm{CO}}_{2}\left(\mathrm{g}\right)+{\mathrm{H}}_{2}\mathrm{O}\left(\mathrm{l}\right)$
3. Identify the reactant which acts as the Bronsted-Lowry base in this reaction. Give a reason for your answer.
4. Use the above equation to explain why the cake rises during this baking process.
(DoE Grade 11 Paper 2, 2007)
2. Label the acid-base conjugate pairs in the following equation: ${\mathrm{HCO}}_{3}^{-}+{\mathrm{H}}_{2}\mathrm{O}⇋{\mathrm{CO}}_{3}^{2-}+{\mathrm{H}}_{3}{\mathrm{O}}^{+}$
3. A certain antacid tablet contains 22.0 g of baking soda (NaHCO ${}_{3}$ ). It is used to neutralise the excess hydrochloric acid in the stomach. The balanced equation for the reaction is: ${\mathrm{NaHCO}}_{3}+\mathrm{HCl}\to \mathrm{NaCl}+{\mathrm{H}}_{2}\mathrm{O}+{\mathrm{CO}}_{2}$ The hydrochloric acid in the stomach has a concentration of 1.0 mol.dm ${}^{-3}$ . Calculate the volume of the hydrochloric acid that can be neutralised by the antacid tablet. (DoE Grade 11 Paper 2, 2007)
4. A learner is asked to prepare a standard solution of the weak acid, oxalic acid (COOH) ${}_{2}$ 2H ${}_{2}$ O for use in a titration. The volume of the solution must be 500 cm ${}^{3}$ and the concentration 0.2 mol.dm ${}^{-3}$ .
1. Calculate the mass of oxalic acid which the learner has to dissolve to make up the required standard solution. The leaner titrates this 0.2 mol.dm ${}^{-3}$ oxalic acid solution against a solution of sodium hydroxide. He finds that 40 cm ${}^{3}$ of the oxalic acid solution exactly neutralises 35 cm ${}^{3}$ of the sodium hydroxide solution.
2. Calculate the concentration of the sodium hydroxide solution.
5. A learner finds some sulfuric acid solution in a bottle labelled 'dilute sulfuric acid'. He wants to determine the concentration of the sulphuric acid solution. To do this, he decides to titrate the sulfuric acid against a standard potassium hydroxide (KOH) solution.
1. What is a standard solution?
2. Calculate the mass of KOH which he must use to make 300 cm ${}^{3}$ of a 0.2 mol.dm ${}^{-3}$ KOH solution.
3. Calculate the pH of the 0.2 mol.dm ${}^{-3}$ KOH solution (assume standard temperature).
4. Write a balanced chemical equation for the reaction between H ${}_{2}$ SO ${}_{4}$ and KOH.
5. During the titration he finds that 15 cm ${}^{3}$ of the KOH solution neutralises 20 cm ${}^{3}$ of the H ${}_{2}$ SO ${}_{4}$ solution. Calculate the concentration of the H ${}_{2}$ SO ${}_{4}$ solution.
(IEB Paper 2, 2003)

what are the isotopes
why don't we insert the negative sign for 5 × 10 - 9 when substituting
Why does an enclosed gas exert pressure on the walls of a container
State the gay lussacs law
what is the coefficient of Na in order to balanced the equation?_Na + MgCl2=2NaCl+Mg?
2
Okuhle
2
Tlotlisang
2
Praise
2
Anna
the combining power of an element, especially as measured by the number of hydrogen atoms it can displace or combine with.
Thanks
REJOYCE
Dealon
what are orbitals
examples of atoms whose Valence energy levels are not full and more to bond and become more stable
Sphe
What is a valency
REJOYCE
what is vacuum
Vacuum, space in which there is no matter or in which the pressure is so low that any particles in the space do not affect any processes being carried on there. It is a condition well below normal atmospheric pressure and is measured in units of pressure (the pascal).
Khayalethu
evidence of reaction
what is the variance if h²4h=5
it's part of chemistry....u have to understand the difference between between hydrogen bonds and the strengthness
I know the difference between hydrogen bonds and strengthness
Deeco
the definition and the applications
when a net force is applied on an object of mass ,it will accelerate in the direction of the net force . Acceleration is directly proportional to the net force and inversely proportional to the of an object
Pride
Deeco
what kind of help u want
Deeco
I'm going to work with you guys
hi
Bandile
hey
Remmington
what are vectors
is the physical quantities that has both magnitude and direction
Dealon