- Understanding the chemical properties of bases and acids
- How do acids and bases react with metals?.
- How do metal carbonates and metal hydrogen carbonates react with acids?
- How do acids and bases react with each other?
- The reaction of metallic oxides with acids
- The reaction of non – metallic oxide with base
- What do all acids and all bases have in common?
- What happens to an acid or base in a water solution?
- How strong are Acid or base solutions?
- Importance of pH in everyday life
- More about Salts
- Family of salts
- pH of salts
- Chemicals from common salt
NCERT solutions for class 10 science chapter 2 acid bases and salts
Consider this situation:
You are given three test tubes. The three test tubes contain distilled water, acidic solution and the basic solution respectively. There is only red litmus paper available in order to identify what is there in each test tube. How will you find out what is in each of the test tubes?
Using the red litmus paper, we can identify the content in each of the test tubes. This can be done by noticing the colour change of the red litmus paper.
- If the red litmus paper changes to blue colour it means that, the solution is a basic solution.
- If we put the changed litmus paper into another solution to see if it changes to red again. If it does change that means that the solution will be an acidic solution.
- The solution that has no change in any of the litmus paper will be the neutral solution therefore that will be the distilled water.
What is the reason behind curd or any other sour substance not to be kept in copper or brass vessels?
Curd and sour food substances contain acids; these acidic substances have a possibility of reacting with the metal. If this reaction takes place then it can cause food poisoning and damage people’s health.
When acids react with metal, which gas is liberated?
If an acid reacts with any metal, salt and hydrogen gas will be formed.
Metal + Acid -> Salt + Hydrogen gas
The reaction of metal A and dilute hydrochloric acid produces a fizz. This gas that is a product of the reaction can extinguish candles. Explain the reaction.
The gas that can extinguish a burning candle is carbon dioxide is formed by the reaction of dilute hydrochloric acid reacts with metal carbonate. When a metal compound ‘A’ reacts with dilute hydrochloric acid, it produces some fizz or effervescence. The compounds formed in this reaction is calcium chloride and it shows that the metal is calcium carbonate. By this, we can state that the compound A is calcium carbonate. Calcium carbonate reacts with the dilute hydrochloric acid to form calcium + carbon dioxide + water. Therefore this product that is formed can extinguish a burning candle.
HCl, HNO3 are compounds that show acidic character in aqueous solutions and on the other hand compounds such as alcohol/glucose don’t show any acidic character. Why is that?
Acids are substances that can dissociate on the dissolving of water, which results in the production of hydrogen ions. Some acids show acidic character as they dissociate in the aqueous solution which results in the production of hydrogen ions (acids like HCl, HNO3).
Compounds similar to glucose or alcohol also do contain hydrogen element but they do not show signs of acidic nature. This is due to the fact that the hydrogen in them will not separate as like the hydrogen in the acids. They will not separate to become hydrogen ions, on dissolving in the water.
What is the reason for an acid aqueous solution conducting electricity?
Due to charged particles, there is electricity that is conducted in aqueous solutions. The charged particles are called ions and they help conduct electricity.
Why does dry litmus paper not change colour in the presence of dry HCl?
Because HCl does not have hydrogen ions present. Therefore does not show any acidic behaviour.
When diluting an acid, why is it important to add acid in the water and not water in the acid?
- Diluting is a process that involves adding concentrated acid to the water. The concentrated water will be added gradually by stirring.
- There is the heat that is evolved slowly and gradually so that concentrated acid is added because diluting acid easily absorbs a large quantity of water.
- If it happens in the other way by adding water to dilute acid the amount of heat evolved is all don’t at once and not gradually. This may cause a splash and could end up in acid burn.
When an acid is diluted, how does it affect the concentration of the hydronium ions H3O+?
When dilution happens and the concentrated solution is mixed with water, it results in the decrease of hydronium ions per unit volume.
How does excess base dissolved in the water affect the concentration of the hydroxide ions?
The solution of the base is diluted when mixed with more water, therefore the concentration of hydroxide ions will decrease per unit volume.
You are given two solutions called E, J their pH is 6 and 8 respectively.
Answer the following:
- Which of the two solutions have more hydrogen ion concentration?
- Which is acidic and which is basic?
In order to find the hydrogen ion concentration, we can use the rule that states, “The pH of any solution is inversely proportional to the hydrogen ion concentration”. Therefore, it means that the solution that has a lower pH number will have a higher hydrogen ion concentration. So it means solution E will have a higher hydrogen ion concentration. In addition, solution J will be basic and E will be acidic.
What is the effect of concentration of the hydrogen ions have on the nature of a solution?
When acids are added to water, they produce hydrogen ions in water, therefore, the concentration of the hydrogen ions will increase in water. Since the solution will have more hydrogen ions, it will definitely be acidic in nature.
Does basic solutions have hydrogen ions? If they do then why are they basic in nature?
Basic solutions do not have hydrogen ions. Since the solution has an excess of hydroxide ions, the basic solution does not have hydrogen ions.
In what condition does a farmer need to treat the soil on his field with quick lime or slaked lime or chalk?
If the soil that is on the field were too acidic then he would have to treat the soil with quicklime. If the soil is, too acidic it means that it will be having a low ph. Therefore the farmer would need to add lime or even slaked lime so that his soil is not too acidic.
Write down the common name for the compound CaOCl2:
It is called bleaching powder.
Give names of substances after the treatment with chlorine will give bleaching powder:
What is the name of the sodium compound that is used to softening hard water?
Write the reaction for the heating of sodium hydro carbonate
2NaHCO3 ——- heat——–> Na2CO3 + H2O + CO2
Why rainwater conducts electricity and distilled water doesn’t?
- Distilled water does not contain any ionic compounds in it.
- Whereas rainwater has a lot, more compounds.
- Rainwater has dissolved acidic gas such as carbon dioxide from the air and that forms carbonic acid. This means that it has hydrogen ions and carbonate ions. Therefore, with the presence of acids, rainwater can conduct electricity.
Why are those acids don’t have their acidic behaviour in the absence of water?
The acidic behaviour from acids is because of the presence of hydrogen ions. Hydrogen ions can only be produced in the presence of water and therefore water is definitely needed if acids are to show their acidic behaviour.
Find out which solution is which with respect to their pH and arrange them in increasing order of hydrogen ion concentration:
|Neutral – A||7|
|Strongly alkaline – B||11|
|Strongly acidic – C||1|
|Weekly acidic – D||4|
|Weekly alkaline – E||9|
In increasing order of hydrogen ion concentration:
pH 11(B) -> pH 9(E) -> pH 7(A) -> pH 4(D) -> pH 1 (B)
There are two test tubes A and B. In the test tube, A HCl is added and in the test tube, B is added. In both the test tubes, magnesium ribbons are kept in both the test tubes. So, find out and explain in which test tube there will be more fizzing give reasons.
HCl is a strong acid where acetic is a weaker acid. The reason why fizzing occurs is because of the evolution of the hydrogen gas by reacting with the acid on the magnesium ribbon. Since HCl is a very strong acid there is a lot of liberation of hydrogen gas from test tube A. therefore, more fizzing take place in test tube A.
Fresh milk from cows has a pH of 6. So how does the pH change when this milk is turned to curd?
The formation of lactic acid is what turns the milk to curd, therefore, it will result in the pH changing below 6.
Why should plaster of Paris be stored in a moisture-proof container?
Moisture can affect it by slowing the setting of the plaster because of hydration. Which will end up making it useless?
What is the meaning of neutralization reaction? Give examples:
The reaction of the acid + base gives a product of salt + water, which is considered a neutralization reaction.
NaOH + HCl -> NaCl + H2O
Mg(OH)2 + H2CO3 -> MgCO3 + 2H2O
What are two important purposes of washing soda and baking soda?
|Washing soda||Baking soda|
|1. It is used as an electrolyte||1. It can be used to test the garden soil for acidity. If bubbles are developed then the soil Is too acidic|
|2. It can be used domestically as water softener for laundry.||2. If used on washing car then it will remove dead bug bodies without damaging the colour or the paint on the car.|
In NCERT solutions class 10 science chapter 2, the conclusion of the lesson is divided into 4 parts. They are – Questions, What have you learnt? Exercises, Group activity. One of the most important parts is Group activity. A few examples of the group activity session is mentioned below.
- Prepare your own index (indicator) – Crush berry in a mortar.
- Add an adequate amount of water to obtain the essence.
- Filter the essence by the process learnt by you in earlier classes.
- Accumulate the filtrate to test the substances you may have tested earlier.
- Fix four test tubes in a test tube stand and name them as P, Q, R and S. Pour 2 ml each of soda-water, vinegar, lemon juice solution and baking soda solution in them accordingly.
- Put 2-3 drops of the berry extract in each test tube and note the colour change if any. Write your observation in a Table.
- You can prepare index by using other natural materials like coloured petals of some flowers such as Hydrangea, Geranium and Petunia; and extracts of red cabbage leaves.
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