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With which substance should chlorine be treated to get bleaching powder?

Chlorine should be treated with dry slaked lime i.e calcium hydroxide to get bleaching powder Ca(OH)2 + Cl2 → CaOCl2 + H2O

ChemistryClass 10ICSE

State the common and chemical names of the compounds formed when plaster of Paris is mixed with water.

When plaster of Paris is mixed with water, it forms gypsum which is calcium sulphate dehydrate. Plaster of Paris is made by heating gypsum at a temperature of 373K

ChemistryClass 10ICSE

What would be the colour of litmus in a solution of sodium carbonate?

Sodium carbonate is a salt formed from a strong base and we know that bases turns litmus red to blue.

ChemistryClass 10ICSE

Which of the following salt has a blue colour and why? CuSO4.5H2O or CuSO4.

CuSO4.5H2O has blue colour due to the presence of water of crystallization. There is a presence of water in the molecule. If it would be anhydrous the colour will be white because it won’t have water molecule. Copper sulphate itself will have no colour due to the absence of water molecule

ChemistryClass 10ICSE

State whether the following statement is true or false: Copper sulphate crystals are always wet due to the presence of water of crystallisation in them.

The statement is false because water of crystallisation is very important part in the crystal structure of salts. It is not free or additional water outside the crystal and it can’t be wet, it is dry always

ChemistryClass 10ICSE

Write the chemical formula of (i) soda ash and (ii) sodium carbonate decahydrate.

Soda ash is having a formula Na2CO3. Chemical name is sodium carbonate Sodium decahydrate is having a formula Na2CO3.10H2 This is washing soda

ChemistryClass 10ICSE

What is the chemical formula of (a) baking soda, and (b) washing soda

Chemical formula of baking soda is NaHCO3 which is a base Chemical formula of washing soda is Na2CO3

ChemistryClass 10ICSE

Hydrochloric acid reacts with a metal X to form a gas Y which burns with a 'pop' sound. Sodium hydroxide solution also reacts with the same metal X (on heating) to form the same gas Y. (a) Name X and Y (b) Write the chemical equation of the reaction of metal X with (i) Hydrochloric acid, and (ii) Sodium hydroxide solution.

X is zinc metal and Y is hydrogen gas which makes a pop sound (i) Zn(s) + 2HCl → ZnCl2 + H2 Zinc reacts with hydrochloric acid to give zinc chloride and hydrogen gas is liberated (ii) 2NaOH(aq) + Zn → Na2ZnO2(aq) + H2 Zinc reacts with sodium hydroxide gives sodium zincate and hydrogen gas is evolved.

ChemistryClass 10ICSE

• A group of students measured the pH of some substances they found in their homes. Their results are given in the following table: Substance pH Apples Baking soda Black coffee Household ammonia Lemon juice Milk Salt Sugar Toothpaste Vinegar Washing soda 3.0 8.5 5.0 12.0 2.5 6.5 7.0 7.0 9.0 3.0 11.5 (a) What would the students have used to measure the pH ? (b) Which solution is the most acidic? (c) Which solution is the most alkaline? (d) Which solutions are neutral? (e) Which solution can be used to treat wasp stings? Which solution can be used to treat bee stings?

<ul><li>To measure the pH universal indicator is used which is having different colours identifying pH from 0 to 14.</li><li>pH 5 Lemon juice is the most acidic which is less than 7</li><li>Household ammonia with pH 12 is the most alkaline</li><li>Salt solution and sugar solution are neutral having pH</li><li>To treat wasp stings vinegar the weak acid can be used as the wasp sting injects alkaline liquid to the</li><li>Baking soda being a base can be used to neutralize the acid which is caused due to the bee It injects methanoic acid to the skin.</li></ul>

ChemistryClass 10ICSE

• (a) Explain why the pH in a person's mouth becomes lower after each meal. (b) What damage could be caused while the pH is low? How could the person change his eating habits to lessen chances of suffering from tooth decay?

The main reason for the low pH in a person’s mouth after each meal is due to the acid formation due to the activity of After meals the sugar in the food item will break down to acids by the bacteria as the acid has low pH acidity increases. While pH in the mouth is low tooth decay can occur which is formed due to the acidity in Tooth decay can be prevented by our self without consulting a Always brush teeth two times a day after having food. Before sleeping brushing is must as the chances of bacterial action is more at the time of sleep. Avoid sweet items like chocolates and ice creams.

ChemistryClass 10ICSE

A first-aid manual suggests that vinegar should be used to treat wasp stings and baking soda for bee stings. What does this information tell you about the chemical nature of: (a) Wasp stings ? (b) Bee stings?

Wasp sting is It injects alkaline liquid to the skin of the person and causes pain and itching sensation. By rubbing vinegar the person will get rid of pain and itching. Bee sting is It injects acidic liquid to the skin of a person and severe pain and irritation persists. Baking soda is a base used to treat the bee sting which neutralizes the acid

ChemistryClass 10ICSE

Solution A turns universal indicator blue to purple whereas solution B turns universal indicator orange to red. (a) What will be the action of solution A on litmus? (b) What will be action of solution B on litmus? (c) Name any two substances which can give solutions like A. (d) Name any two substances which can give solutions like B. What sort of reaction takes place when solution A reacts with solution B?

Solution A turns universal indicator blue to purple so it is basic in nature and will turn litmus Solution B turns universal indicator orange to red so it is acidic in nature and will turn litmus Milk of magnesia and sodium hydroxide solution are like solution A Lemon juice and hydrochloric acid are like solution B Neutralisation reaction takes place between A and B which produces salt and water

ChemistryClass 10ICSE

Here are some results of solutions tested with universal indicator paper: Sulphuric acid Metal polish Washing-up liquid Milk of magnesia Over cleaner Car battery acid Red Dark blue Yellow Light blue Purple Pink Arrange the solutions in order of their increasing pH values (starting with the one with the lowest pH).

The solutions have been arranged below in the increasing order of their pH values Sulphuric acid (pH 1) < Car battery acid (pH 2) < Washing-up liquid (pH 5) < Milk of magnesia (pH 9) < Metal polish (pH 12) < Oven cleaner (pH 14)

ChemistryClass 10ICSE

Which solution is (i) weakly alkaline (ii) neutral (iii) strongly acidic (iv) strongly alkaline, and (v) weakly acidic?

D : Weakly alkaline having pH = 11 C : Neutral having pH = 7 A: Strongly acidic having pH = 1 E : Strongly alkaline having pH = 13 B: Weakly acidic having pH = 5

ChemistryClass 10ICSE

Potatoes grow well on Anhad's farm which has soil with a pH of 5.5. Anhad decides to add lot of lime to soil so that he can grow broccoli in the same farm: (a) Do potatoes grow better in acidic or alkaline soil? (b) Does broccoli grow better in acidic or alkaline soil?

Potatoes grow in the soil having acidic nature of pH 5 Broccoli grows better in alkaline soil because he added a lot of lime to the soil which is acidic and seems more basic.

ChemistryClass 10ICSE

Which of the following elements would form oxides which would indicate pH values less than seven, using moist pH paper? Magnesium, Carbon, Sulphur, Hydrogen, copper

Both sulphur and carbon burn in the air to form sulphur dioxide and carbon dioxide. Both are having pH less than 7 which indicates acidic oxides. Hydrogen will form water by reacting with oxygen and the pH will be 7 as it is neutral. Magnesium and copper does not form oxides which having less than pH 7 The pH values of five solutions A, B, C, D and E are given below: A B C D E 1 5 7 11 13

ChemistryClass 10ICSE

The daffodil plant grow best in soil having a pH range of 6.0 to6.5. If the soil in a garden has a pH of 4.5, which substance needs to be added to the soil in order to grow daffodils? Solutions: (a) Salt (b) Lime (c) Sand Compost

Option (b) is the answer. If the pH of the soil is 4.5 it indicates the soil is acidic and the soil should be treated with a base like quick lime or slaked lime it further neutralizes the acid.

ChemistryClass 10ICSE

The acid produce naturally in our stomach is : (a) Acetic acid (b) Citric acid (c) Hydrochloric acid Sulphuric acid

Option (c) is the answer. Hydrochloric acids produces naturally in our stomach in the process of digestion in a certain amount, if it exceeds then it causes acidity or ulcer.

ChemistryClass 10ICSE

Fresh milk has a pH of 6. When milk changes into curd, the pH value will: (a) Become 7 (b) Become less than 6 (c) Become more than 7 Remain unchanged

Option (b) is the answer. Fresh milks when converted into curd will produce lactic acid. The value of pH for an acid will always lesser than 7.

ChemistryClass 10ICSE

It has been found that rubbing vinegar on the stung area of the skin of a person gives him relief. The person has been stung by: (a) Wasp (b) Ant (c) Honey bee Nettle leaf hair

Option (a) is the answer. Wasp sting injects alkaline solution and thus rubbing with an acid like vinegar will give relief from pain and irritation caused by the wasp.

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