Acids, Bases and Salts

A substance `X` used in the kitchen for making tasty crispy pakoras.and is also an

ingredient of antacid. Name the substance `X`.

(i) How does `X` help to make cakes and bread soft and spongy.

(ii) Is the pH value of solution of `X` is lesser than or greater than 7.0?

A student heated a few crystals of copper sulphate in a dry boiling tube.

(a) What will be the color of the copper sulphate after heating?

(b) Will you notice water droplets in the boiling tube?

(c) Where have these come from?

A few drops of phenolphthalein indicator were added to an unknown solution

A. It acquired pink colour. Now another unknown solution B was added to it

drop by drop and the solution becomes colorless. Predict the nature of A & B.

A compound `A on heating at 370 K gives `B` used as plaster for supporting

fractured bones in the right position. `B` on mixing with water changes to `A`.

Identify `A` and `B` and write the chemical reaction

When CO2 gas pass through saturated solution of ammonical brine, two

compound `X` and `Y` are formed. `Y` is used as antacid and decomposes to

form another solid `Z`. Identify `X`,`Y`, `Z` and write chemical equations.

A yellow powder X gives a pungent smell if left open in air. It is prepared by

the reaction of dry compound Y with chlorine gas. It is used for disinfecting

drinking water. Identify X and Y. and write the reaction involved.

A compound `X` on electrolysis in aqueous solution produces a strong base.

`Y` along with two gases `A` and `B`. `B` is used in manufacture of

bleaching powder. Identify X, Y, A and B. Write chemical equations.

A road tanker carrying an acid was involved in an accident and its contents

spilled on the road. At the side of the road, iron drain covers began melting

and fizzing as the acid ran over them. A specialist was called to see if the

acid actually leaked into the nearby river.

(a) Explain how the specialist could carry out a simple test to see if the

river water contains some acid or not.

(b) The word melting is incorrectly used in the report. Suggest a better

name that should have been used.

(c) Explain why drain covers began fizzing as the acid rain over them.

`A` is a soluble acidic oxide and `B` is a soluble base. Compared to pH of

pure water. What will be the pH of (a) solution of A (b) solution of B?

. A first aid manual suggests that vinegar should be used to treat wasp sting

and baking soda for bee stings.

(i) What does this information tell you about the chemical nature

of the wasp stings

(ii) If there were no baking soda in the house, what other household

substance could you use to treat bee stings?

The oxide of a metal M was water soluble when a blue litmus strip was

dipped in this solution, it did not go any change in colour. Predict the nature

of oxide

Compound P forms enamel of teeth. It is the hardest substance of the body.

It does not dissolve in water but it is corroded when pH in the mouth is below

How does tooth paste prevent dental decay?

A compound X is bitter in taste. It is a component of washing powder& reacts

with dil.HCl to produce brisk effervescence due to colourless, odourless gas

Y which turns lime water milky due to formation of Z. When excess of CO2

is passed, milkiness disappears doe to formation of P. Identify X, Y, and Z &

P.

Kazi and priyam want to prepare dil H2SO4 .Kazi added conc.H2SO4 to water

slowly with constant stirring& cooling whereas Priyam added water to conc.

H2SO4.Name the student who was correct and why?

Acid when react with metals release hydrogen gas but there is one acid which when reacts with metals does not release hydrogen except for two metals. Prove this statement.

Dry hydrogen chloride gas does not turn blue litmus, whereas hydrochloric acid does. Why? 

Dry hydrogen chloride gas does not turn blue litmus, whereas hydrochloric acid does. Why? Ans.      In the dry state, hydrogen chloride (HCl) does not release H+  ions. Therefore, it cannot behave as an acid. When dissolved in water, it forms hydrochloric acid. It dissociates to give H+ ions in solution and behaves as an acid.

In one of the industrial process used for manufacture of sodium hydroxide, a gas ‗X‘  is formed as by – product. The gas ‗X‘ reacts with lime water to give a compound ‗Y‘ which is used as a bleaching agent in chemical industry. Identify ‗X‘ and ‗Y‘ giving the chemical equation of the reaction.

A doctor applied surgical bandage in the fractured bones of a patient after making them wet. What changes are likely to occur?

Define pH.

Where is Hydrogen used as fuel.

Acetic acid is highly soluble in water but is still a weak acid .Why.

(a) How is bleaching powder prepared. (b) What happens if bleaching powder is exposed to air for a long time. (c) Give its uses.

Why tartaric acid added into baking soda to get baking powder.

Solutions A, B, C,D have pH values 3,4,5,6 respectively. Arrange them in increasing order of acidic characteristic .giving reason.

Explain the importance of pH in daily life.

What is Acid rain? What is its pH? How does it affect the aquatic life?

What is difference between a base and a alkali .explain with suitable example.

How is Plaster of Paris is prepared .What reaction take place when it sets to hard.

Rain water and tap water conduct electricity but distilled water does not .Explain why.

Name two metals which react with sodium hydroxide solution to produce hydrogen gas .give the reaction.

Glucose, alcohol contains hydrogen yet their solutions do not turn blue litmus red. Why.

Why we should not keep curd in cooper or brass vessel .What treatment should be given to these vessels before use.

Give two important uses of washing soda and baking soda.

What is a neutralization reaction? Give two examples.

Plaster of Paris should be stored in a moisture-proof container. Explain why?

A milkman adds a very small amount of baking soda to fresh milk.

(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?

(b) Why does this milk take a long time to set as curd?

Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid(CH₃COOH) is added to test tube B. In which test tube will the fizzing occur more vigorously and why?

Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9, respectively. Which solution is

(a) neutral?

(b) strongly alkaline?

(c) strongly acidic?

(d) weakly acidic?

(e) weakly alkaline?

Arrange the pH in increasing order of hydrogen-ion concentration.

Why do acids not show acidic behaviour in the absence of water?

Why does distilled water not conduct electricity, whereas rain water does?

Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an activity to prove it.

Write word equations and then balanced equations for the reaction taking

place when −

(a) dilute sulphuric acid reacts with zinc granules.

(b) dilute hydrochloric acid reacts with magnesium ribbon.

(c) dilute sulphuric acid reacts with aluminium powder.

(d) dilute hydrochloric acid reacts with iron filings.

Which one of the following types of medicines is used for treating indigestion?

(a) Antibiotic

(b) Analgesic

(c) Antacid

(d) Antiseptic

10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralise it will be

(a) 4 mL (b) 8mL (c) 12 mL (d) 16 mL

A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains

(a) NaCl (b) HCl (c) LiCl (d) KCl

A solution turns red litmus blue, its pH is likely to be

(a) 1 (b) 4 (c) 5 (d) 10

Write an equation to show the reaction between Plaster of Paris and water.

What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.

Name the sodium compound which is used for softening hard water.

Name the substance which on treatment with chlorine yields bleaching powder?

 What is the common name of the compound CaOCl₂?

Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)?

 Do basic solutions also have H⁺ ions? If yes, then why are these basic?

 What effect does the concentration of H⁺ions have on the nature of the solution?

You have two solutions, A and B. The pH of solution A is 6 and pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?

How is the concentration of hydroxide ions (OH−) affected when excess base is dissolved in a solution of sodium hydroxide?

While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

Why does dry HCl gas not change the colour of the dry litmus paper?

Why does an aqueous solution of an acid conduct electricity?

Why do HCl,HNO₃  etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?

:  

Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?

Why should curd and sour substances not be kept in brass and copper vessels?

You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?