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VERY SHORT ANSWER QUESTIONS
Question 1)Write the neutralization reaction of acids? Question 2Write the name of the products obtained when zinc metal pieces are dropped into sodium hydroxide bottle. Solution
2NaOH +Zn-> Na2ZnO2 + H2
Products are Sodium zincate and hydrogen
Question 3) What is the nature of baking soda? Question 4)What are olfactory indicators? Solution
olfactory indicators are those indicators that help to identify whether the given solution is acidic or basic by changing their smell instead of colour as other indicators do.
olfactory indicator" implies that this is a compound whose can smell you can detect... vanilla, clove and onion are all olfactory indicators as these do not give their distinct odour in highly alkaline(basic) medium.
Question 5) Write an equation for the action of dilute hydrochloric acid on marble chips. Solution
arble is nothing but calcium carbonate
CaCO3 + HCl -> CaCl2 + H20 + CO2
Question 6) Write the chemical name and formula of washing soda? Solution
Question 7) Write the preparation of sodium hydroxide? Question 8) Name the raw materials required to manufacture bleaching powder. Question 9) Write the chemical formula of plaster of paris and gypsum? Question 10) What happen when excess of CO2 passes from lime water? Question 11) Why does dry HCI gas not change the colour of the dry litmus paper? Question 12) What effect does the concentration of H+ (aq) have on acidic nature of the solution? Question 13) Write the reaction between dilute NaOH solution and dilute HCI acid. Question 14) Why does an aqueous solution of an acid conduct electricity? Question 15)What is chloro- alkali process. Solution
When concentrated solution of sodium chloride is electrolysed it forms Chlorine gas, Sodium hydroxide and Hydrogengas. It is called chlor-alkali process because of the products formed- Chlor for chlorine gas and alkali for Sodium hydroxide. Chlorine is formed at anode and Hydrogen is formed at the cathode and Na(OH)2 is formed near the cathode.
The main products formed are: Chlorine and Sodium Hyroxide
Question 16) Write the name and the chemical formula of the organic acid present in vinegar. Solution
name of the acid - acetic acid (CH3C00H)
Question 17) What are alkalies? Given one example of alkalies? Question 18) Is Water a strong acid or a weak acid? Question 19) What is the common name of the compound CaOCl2? Solution
Calcium Oxy chloride. Comman name is bleaching power
Question 20) Name the acids present in wasp sting. Question 21) what is the pH of a neutral solution? Solution
Question 22) Name two indicators which are widely used in laboratories. Question 23) What are olfactory indicators? Give an example Question 24) What is brine? Question 25) What happens to the temperature of water when few drops of concentrated sulphuric acid is added to it? Question 26) Which compound of sodium is used for softening of hard water?
SHORT ANSWER QUESTIONS
Question 1) Why do HCI, HNO3 etc., show acidic characters in aqueous solution while solutions of compounds like alcohol and glucose do not show acidic character? Question 2) What are hydronium ions? Question 3) What is meant by strong acids and weak acids? Classify the following into strong acids and weak acids :-
HCl, HNO3, H2CO3, H2SO3, CH3COOH Solution
A strong acid dissociates completely (100%)
A weak acid is only partly dissociated (less than 100%)
A strong acid has a pH 1.
pH of weak acid is 3-5
Hydrochloric acid, sulphuric acid.
Acetic acid, Formic acid
All the HCl molecules becomes into hydrogen ions & chloride ions when they are dissolved in water
Some of the acid molecules become ions. most of them stay as acid molecules
Question 4) What happens when a solution of sodium hydrogen carbonate is heated? Write equation of the reaction is involved. Question 5)What happens when base react with non metal oxide? Question 6) What is water of crystallization? Give some examples of salt having water of crystallization? Give some example of salt having water of crystallization? Question 7) Classify each of the following substance as a weak acid, strong acid, weak base, strong base, both a weak acid and a weak base, or neither an acid nor a base :
Question 8) What would happen if a small amount of copper oxide is taken in a beaker and dil. HCI is added to it? Question 9) How does plaster of paris reacts with water? Write down the chemical equation? Question 10) What is dilute? Why care must be taken while mixing concentrated nitric acid or sulphuric acid with water? Question 11) Show with the help of an equation show that metal carbonates liberate carbon dioxide on reaction with dilute acid. Question 12) Write the balanced molecular equations showing the complete neutralizations of the following.
HNO3 by NaOH
Ca(OH)2 by HI
HNO3 by KOH Solution
Question 13) Write the formulas of the acid and the base that formed the following salts.
CH3COONa: CH3COOH and NaOH
CuSO4: H2SO4 and Cu(OH)2 KClO3: HClO3 and KOH
Al2(SO4)3 : Al(OH)3 and H2SO4 NH4Cl: NH4OH and HCL Ba(NO2): Ba(OH)2 and HNO2 NH4NO3: NH3 and HNO3
Question 14) Write two observations you would make when quicklime is added to water. Question 15) What are the uses of Bleaching powder? Solution
(i) It is used for bleaching cotton and linen in the textile industry, for bleaching wood pulp in paper factories and for bleaching washed clothes in laundry
(ii) It is used as an oxidising agent in many chemical industries
(iii) It is used for disinfecting drinking water to make it free of germs
Question 16) State the chemical property in each case on which the following uses of baking soda are based :-
as an antacid
as a constituent of baking powder. Question 17) How is plaster of Paris obtained? What reaction is involved in the setting of a paste of plaster of Paris? Question 18)Acids show their properties only in the presence of water? explain? Question 19)A weak acid is added to a concentrated solution of hydrochloric acid. Does the solution become more or less acidic? Question 20) Write the chemical name and formula of washing soda. What happens when crystals of washing soda are exposed to air? Solution
Write word equations and then balanced equations for the reaction taking place when-
dilute sulphuric acid reacts with zinc granules.
dilute hydrochloric acid reacts with magnesium ribbon.Give two important uses of caustic soda and baking soda.
On which factors does the strength of an acid or a base depend? Explain.
Question 22)Explain the following by giving examples:
a. how metal oxides react with acids?
b.How non- metal oxides react with baes? Question 23) a)Why does acidic solution conduct electricity?
(b)Can basic solution conduct electricity?
(c)Can separation of H+ ions in acids take place when HCI is added to a non- aqueous solution? Solution
Both acidic and basic solutions in water conduct electricity. Acids, when dissolved in water release the H+ and bases when dissolved in water release the OH- ions. These ions are charged species and so act as charge carriers. In other words the conductivity of these solutions is due to the movement of these ions.
LONG ANSWER QUESTIONS Question 1) How common salt prepared from sea water? Solution
Sea water contains a large amount of common salt and the salts of other metals dissolved in it. Near the sea-shore, the sea water is collected in shallow pits and allowed to evaporate in sunshine. In a few days, the water evaporates, leaving behind salt. The salt so obtained is collected and transported to big factories, where it is purified and packed for consumtions
Question 2) What is observed when – (i) dilute sulphuric acid is added to solid sodium carbonate. (ii) hot concentrated sulphuric acid is added to sulphur. (iii) Sulphur doioxide is passed through lime water? Also write chemical equations to represent the chemical reaction taking place in each case. Question 3) A student dropped few pieces of marble in dilute hydrochloric acid, contained in a test tube. The evolved gas was then passed through lime water. What change would be observed in lime water? What will happen if excess of gas is passed through lime water? Write balanced chemical equations for all the changes observed. Question 4) A compound X of sodium forms a white powder. It is a constituent of baking powder and is used in some antacid prescriptions. When heated, X gives out a gas and steam. The gas forms a white precipitate with limewater. Write the chemical formula and name of X and the chemical equation for its decomposition on heating. What is its role in baking powder and in antacids? Solution
Baking powder consists of sodium bicarbonate, tartaric acid and small amount of starch. Hence, the compound X of sodium in question which is a constituent of baking powder and is used in antacids is sodium bicarbonate or sodium hydrogencarbonate, which has the chemical formula NaHCO3. It is commonly known as baking soda.
On heating, it decomposes to give sodium carbonate, water and carbon dioxide.
NaHCO3 -> Na2CO3 + H2O +CO2
This gas(CO2) when passed through lime water turns it milky due to the formation of calcium carbonate, which is insoluble in water.
Ca(OH)2 + CO2 ? CaCO3 + H2O
a milk man adds a very small amount of baking soda to fresh milk:
Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
What do you expect to observe when fresh milk comes to boil?
Why does this milk take a long time to set as a curd?
The colour of litmus paper changes only in the presence of ions like hydrogen (H+) or hydronium (H3O+) ions. HCl can produce these ions only in the form of aqueous solution. Hence dry HCl gas does not change the colour of dry litmus paper
Antacid reacts with acid in the stomach and neutralizes it
Question 8) (a)What is pH scale and what’s its range? How is it related to hydronium ion concentration?
(b)Explain any two roles played by pH levels of various chemicals in living organisms. Solution
The term “pH” is defined as the negative logarithm of H+ ion concentration of a given solution; the concentration being expressed as moles per litre.
athematically pH = – log [H+] ‘pH’ stands for: Power of hydrogen ion concentration, ‘p’ for power and ‘H’ for H+ ion concentration.
Some important benchmark values in the pH scale are: pH = 7 indicates neutral solutions e.g., aqueous solutions. pH > 7 to 14 indicates alkaline solutions and pH < 7 to 0 indicate acidic solutions
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