A.Tick the correct answer:-
1.d 2.b 3.b 4.d 5.a
B.Differentiate between the following:-
1. An acidic compound containing replaceable hydrogen, a part or whole of which may be replaced, directly or indirectly by metal to produce salt.
A base is a substance usually the oxide or the hydroxide of a metal which can neutralize the by an acid to produce the salt and water.
2.Organic acids are acids present in plant materials and animals. These are naturally occurring acids.
A mineral acid is an acid derived from one or more minerals of the earth.
3.A strong acid is one which dissociates easily to give hydrogen ion. example hydrochloric acid(Hcl)
A weak acid does not dissociate easily. example formic acid(HCOOH)
4.A base is a substance usually the oxide or hydroxide of a metal which can neutrilize an acid to produce salt and water.
C.Give one word answer for each of the following:-
1.Citric acid 2.Sodium bicarbonate (NaHCO₃ ) 3. Formic acid 4. Mineral acids 5. Alkali
D.Match column A with column B:-
1.Blue litmus red 2. neutral substance 3.alkali 4.changes colour when 5.neutralization 6.bitter in test
E.Give two example for each of the following:
1. H₂SO₄,HNO₃ 2. KOH,NaOH 3. Na₂CO₃,Nacl 4.litmus ,methyl orange
F.Give reasons for each of the following:-
1.When an acid is added to a base than neutralization reaction takes place producing salt and water.
2.When an acid say sulfuric acid, H₂SO₄ is added to water then hydrates are formed with the evolution of heat because exothermic reaction takes place. Hence reaction mixture becomes hot.
3.All acids contain hydrogen ion (H+). Those acids who release (H+) in solution quickly are called strong acid and if not they are called weak acids.
4.Because they are made in the laboratory artificially. example methyl orange.
G.Write true or false:-
1.True 2.false 3.true 4.true 5.false
H.Circle the odd one out:-
1.Sodium bicarbonate 2.sugar solution 3.natural dye 4.methyl orange 5.acids
I.Fill in the blanks:-
1.Mineral 2.red 3.alkali 4.caustic soda 5.table salt
J.Short answer question:-
1.An acid is a compound containing replaceable hydrogen, a part or whole of which may be replaced directly or indirectly by metal to produce salt.
2.A base is a substance usually the oxide or hydroxide of a metal which can neutrilize an acid to produce salt and water only.
3.An indicator is a substance which indicate by change of their colour to know whether a solution is acid / base / neutral.
4.Turmeric, Hibiscus flower
5.Strong base_---> NaOH,KOH
weak base---->Mg(OH)₂,Zn(OH)₂
6.A salt is a compound formed by partial or complete replacement of the replaceable hydrogen atom of an acid by metal.
7.Neutralisation means reaction between acid and base to form salt and water. example
Hcl+NaOH-->Nacl+H₂O
Acid Base Salt Water
K.Long answer question:-
1.Properties of acids:
(A) Physical property
(i) Acids have a sour taste
(ii) Acids turn blue litmus red
(iii) Acids are corrosive in nature
(iv) All acid contain hydrogen ion
(v) Acid react with carbonate to produce carbon dioxide, used as fire extinguisher
(vi) Acid have a pungent odour
(vii) Some acids exist in solid state example citric acid
(B) Chemical properties
(i) Most acid liberate hydrogen gas on react with metal example
2Na+Hcl-->₂Nacl+H₂
Zn+₂Hcl-->Zncl₂+H₂
(ii)Reaction of acids with carbonates example
Na₂CO₃+2Hcl-->₂Nacl+H₂O+CO₂
NaHCO₃+Hcl-->Nacl+H₂O+CO₂
2. Acids are of two types on the basis of their occurrence, organic or natural acids and mineral acids
Organic acids-- Acids which are obtained from natural sources are called natural or organic.An organic acids is an organic compound and posses acidic properties. The most common organic acids are carboxylic acids (having carbonyl group,-COOH) sulphuric acid (having group -SO₃H) and alcohols (with -OH group)
Generally the organic acids are weak acids and do not dissociate completely in water but are soluble in organic solvents.
Mineral acids- A mineral or inorganic acid is an acid derived from one or more minerals or inorganic compounds. All mineral acids form hydrogen ions. They are soluble in water and insoluble in organic solvents. Mineral acids are sometimes referred as man made as it because these can be manufactured at commertial level for various purposes. They are also termed as laboratory acids. Some of the important mineral acids are sulphuric acid( H₂SO₄ ), phosphoric acid( H₃PO₄ ), boric acid(H₃BO₃) , and nitric acid( HNO₃). We use these mineral acid in our day to day life. example we use Hcl for cleaning kitchen. Sulphuric acid is used in car batteries, inverters etc. Goldsmith uses nitric acid for cleaning gold and silver ornaments. Concentrated mineral acid are very harmful for our skin.
3.Properties of bases
(a)Bases are soapy to touch and bitter in taste
(b)Bases turn red litmus paper blue
(c)All bases contain hydroxyl group(-OH)
(d)Bases react with an acid to form salt and water. This is called neutralization reaction.
(e)Bases should not be touched by hand
(f)Some bases are soluble in water and are called alkali
4.On the basis of acidity bases can be classified into three types monoacidic, diacidic and triacidic. Acidity of base- The acidity of a base is its power of neutralizing an acid and is measured by the number of replaceable hydrogen groups contained in a molecule of base. Thus KOH,NaOH are monoacidic bases, Zn(OH)₂,Ca(OH)₂ are diacidic bases, Bismuth hydroxide Bi(OH)₃ Alminium hydroxide Al(OH)₃ are triacidic bases.
5.Indicators are substance which indicated by the chemical change of colour whether a substance is acidic or basic or neutral.
Types of indicators: Indicators can be divided into two type the first type is natural indicators that are obtained from naturally occurring substance such as litmus turmeric China rose. The second type is synthetic indicator that are made in laboratory such as phenolphthalein and methyl orange etc.
Indicator colour in acidic medium colour in basic medium
1.Phenolphtalein Colourless Red
2.Methyl orange Red Yellow
3.Litmus Red Blue
4.China rose Pink Green
5.Turmeric Yellow Red
6.Salts- A salt is a compound formed by the partial or complete replacement of the replaceable hydrogen atom or atoms by a metal.
Salt are of three kinds-- normal salt, acidic salt and basic salt.
Acid salt-- A salt produced by the displacement of a portion only of the replaceable hydrogen atom present in the molecule of an acid by a metal e.g
Normal salt--A salt produced by the NaHCO₃ displacement of all the replaceable hydrogen atoms present in the molecule of an acid by a metal. example Na₂SO₄ etc
Basic salt e.g Cu(OH)₂,Pb(OH)₂ etc
7.Neutralization-- All bases react with acids to form salt and water. This process is known as neutralization. Acids and bases are chemically opposite. e.g
Hcl+NaOH-->Nacl+H₂O
Hydrochloric acid+sodium hydroxide-->sodium chloride+water
HNO₃+NaOH-->NANO₃+H₂O
H₂SO₄+₂NaOH-->NaSO₄+2H₂O
sulphuric acid sodium sulphate
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