Acids
Dry hydrogen chloride gas does not turn blue
litmus red whereas dilute hydrochloric acid does.
Dry HCl gas does not dissociate into ions, so it
has no effect on the litmus. Hydrochloric acid
form ions, so it turns blue litmus red.
A chemical compound 'X' is used in the soap and glass industry. It is prepared from brine.
Write the chemical name, common name and chemical formula of 'X'.
NaOH
The metal salt ‘A’ is blue in colour. When salt ‘A’ is
heated strongly over a burner, then a substance ‘B’
present in it is eliminated and a white powder ‘C’ is
left behind. When a few drops of a liquid ‘D’ is added
to powder ‘C’, it becomes blue again.
Identify A, B, C and D.
‘A’ is CuSO4.5H2O,
‘B’ is H2O,
‘C’ is CuSO4 (ahydrous).
A solution 'X' gives orange colour when a drop of it falls on pH paper, while another solution 'Y' gives bluish colour when a drop of it falls on pH paper. What is the nature of both the solutions ?
'X' is acidic solution having pH range 3-4. 'Y' is basic solution having pH 9.
Fresh milk has a pH of 6. To delay its curdling, a chemical substance is added to it, which is
Baking Soda NaHCO3
Why do acids not show acidic behaviour in the absence of water?
Acids produce hydrogen ions (H⁺) only in the presence of water. These ions are responsible for the acidic properties. Without water, acids cannot ionize, so they do not exhibit acidic behaviour.
A farmer adds substance A to acidic soil. A has a basic nature and raises the pH of soil from 5.2 to around 7. Identify A and write the type of reaction.
A = Calcium hydroxide or quick lime
Neutralization reaction
Salt A is white and is used in the preparation of bleaching powder. It shows no water of crystallization. Compound B is reacted with C to produce A. D is a safety warning associated with B.
Identify A, B, C, and D.
👉 Answer:
A = Calcium hydroxide (Ca(OH)₂)
B = Chlorine gas (Cl₂)
C = Dry slaked lime (Ca(OH)₂)
D = Chlorine gas is toxic and corrosive
When a drop of solution is added to Indicator A, it turns orange. The original solution has a pH around 4. Identify the nature of the solution and name the indicator.
Nature = Acidic
Indicator A = Methyl orange
At five, I start to eat your teeth,
Below that, there’s no relief.
Your enamel falls if I persist—
That’s why brushing should not be missed!
Tooth-decaying pH (Below 5.5)
Which acid among HNO₃, CH₃COOH, and HCN is a weak acid, and why?
HCN (Hydrocyanic acid) – It only partially ionizes in water
Which base is used in the whitewashing of walls?
Calcium hydroxide (Ca(OH)₂)
HE HE HE
Free Points Enjoiiiii
Indicator A turns yellow in acids and red in bases. A is sprinkled on soap solution and the cloth turns red. Identify A and conclude the nature of soap solution.
A = Turmeric
Soap solution is basic
Add me to water, I hiss and heat,
In whitewashed walls, my work’s complete.
My oxide self starts the game,
But slaked is what becomes my name.
Calcium hydroxide (Ca(OH)₂)
Compound A is an acid found in the stomach that helps digestion. When excess of A causes discomfort, an antacid containing compound B is used. The reaction forms salt C and water. Identify A, B, and C.
A = Hydrochloric acid (HCl)
B = Magnesium hydroxide (Mg(OH)₂)
C = Magnesium chloride (MgCl₂)
(HCl + Mg(OH)₂ → MgCl₂ + H₂O)
I’m not sugar, but I taste quite bitter,
I’ll burn your skin, yet clean your litter.
In drains I slip and clear the way—
Don’t touch me bare, keep burns at bay!
Sodium hydroxide (NaOH)
A salt A gives a reddish-brown gas B when heated. It is used in fertilizers. When water is added to the hot residue, a green compound C forms. D is the acid used to prepare A in lab.
Identify A, B, C, and D.
👉 Answer:
A = Ammonium nitrate (NH₄NO₃) or Ferrous sulphate (FeSO₄·7H₂O)
(More likely FeSO₄·7H₂O based on green compound)
B = Nitrogen dioxide (NO₂)
C = Ferrous hydroxide or hydrated iron compound
D = Sulphuric acid (H₂SO₄)
In neutral lands, I’m silent, pale—
In base I bloom, in acid I fail.
My blush is pink, but not in rain—
With strong alkali, I glow again.
Phenolphthalein
On your salad I may land with flair,
Though I sting your nose, I’m everywhere.
A carboxyl in my core, I’m weak yet known—
For preserving pickles, I sit on the throne.
Who am I?
Acetic acid (CH₃COOH)
White on chips, I fizz when wet,
With acid friends, I’m quite upset.
I bubble and make a cloudy show—
In lime water, that gas will glow!
Who am I?
Calcium carbonate (CaCO₃)
Pink with phenolphthalein, I come alive,
In oven cleaners, I help things survive.
Electrolyte in some batteries too—
My name starts with K, that’s your clue!
Who am I?
KOH
In a chemical industry, compound A is electrolysed.
At the cathode, B is formed, which is collected and compressed for industrial use.
At the anode, C is formed and sent for manufacturing compound D, used in the production of plastics like PVC.
Identify A, B, C, and D.
👉 Answer:
A = Brine (NaCl solution)
B = Hydrogen gas (H₂)
C = Chlorine gas (Cl₂)
D = Vinyl chloride (for PVC production)
Which indicator would be most suitable for titration of a strong acid with a strong base? Justify.
Which indicator would be most suitable for titration of a strong acid with a strong base? Justify.
I’m a number that shows your might,
If you’re an alkali or acidic in fight.
At ten I’m strong, at four I sting—
What am I that pH values bring?
Hydrogen ion concentration