Have you ever thought about what happens when you put an eggshell into nitric acid? This is a chemistry experiment that you often see in JEE questions about acids, bases and salts.<\/p>\n\n\n\n
As someone who wants to ace the JEE Main Exam, knowing these reactions can get you marks in physical chemistry when it comes to acids, bases and salts and especially in JEE questions, about acids, bases and salts.<\/p>\n\n\n\n
Egg shells aren’t just trash; they’re mostly calcium carbonate, or CaCO\u2083, about 95% of their makeup. That’s the key player here.<\/p>\n\n\n\n
Calcium carbonate behaves as a basic salt because the carbonate ion reacts with acids. In JEE, remember CaCO\u2083 shows up in chapters on acids reacting with carbonates.<\/p>\n\n\n\n
Farmers even grind shells for soil to neutralise acidity, but for us, it’s pure exam gold.<\/p>\n\n\n\n
Nitric acid, HNO3, is a strong acid, fully dissociating in water to give H+ and NO\u2083- ions. It’s corrosive and oxidising, but in this reaction, it’s the acidity that drives things.<\/p>\n\n\n\n
In JEE Main, questions often test strong acids like HNO\u2083, HCl, or H\u2082SO\u2084 versus weak ones. HNO\u2083 completely ionises in water, producing a highly acidic solution with low pH. <\/p>\n\n\n\n
Handle it with gloves; real lab safety matters for practicals too.<\/p>\n\n\n\n
Drop crushed eggshell into dilute nitric acid, and watch bubbles form fast. That’s CO\u2082 gas escaping, causing brisk effervescence.<\/p>\n\n\n\n
The balanced equation is straightforward:<\/p>\n\n\n\n
CaCO\u2083 + 2HNO\u2083 \u2192 Ca(NO\u2083)\u2082 +CO\u2082 + H\u2082O<\/p>\n\n\n\n
Calcium carbonate from the shell swaps with hydrogen ions, forming soluble calcium nitrate, water, and gas.<\/p>\n\n\n\n
This is primarily an acid\u2013carbonate reaction producing salt, water, and carbon dioxide. Carbonic acid (H\u2082CO\u2083) forms momentarily and decomposes into CO\u2082 and H\u2082O.<\/p>\n\n\n\n
The shell dissolves slowly as CaCO\u2083 reacts away, leaving a clear solution if excess acid.<\/p>\n\n\n\n
First sign? Fizzing like a soda bottle shaken up. Pass the gas through limewater; it turns milky due to the formation of CaCO\u2083 precipitate. Classic test for CO\u2082 in JEE syllabi.<\/p>\n\n\n\n
Solution heats a bit, an exothermic reaction. Color? Nitric acid might tint yellow, but products stay colourless.<\/p>\n\n\n\n
For JEE preparation, sketch this: solid dissolving, gas evolving. Questions ask “brisk effervescence due to?” Answer: CO\u2082 from carbonate-acid reaction.<\/p>\n\n\n\n
This is an acid-carbonate reaction, under double displacement or neutralisation broadly. Carbonate + acid always gives salt, water, and CO\u2082.<\/p>\n\n\n\n
In the acids, bases, and salts chapter (Class 10 base, but JEE revisits), it’s decomposition too for unstable H\u2082CO\u2083.<\/p>\n\n\n\n
Compare with HCl:<\/strong> same products except CaCl\u2082. HNO\u2083 is specific because nitrate is soluble, no ppt. JEE twists: Concentrated nitric acid is a strong oxidising agent and may produce nitrogen oxides (NO\u2082) instead of behaving only as a simple acid. <\/p>\n\n\n\n Similar questions are frequently asked in JEE Main and NCERT-based MCQs: “Eggshell + dil acid observes?” Options: effervescence, no reaction, etc. Straight from NCERT.<\/p>\n\n\n\n Net ionic skips spectators. Links to p-block (carbonates), coordination (nitrates). PYQs test observation, equation, gas test. Search “acids, bases, salts JEE PYQ<\/a>” for mocks.<\/p>\n\n\n\n Chapter weightage: 4-5% in Main, builds for equilibrium (solubility).<\/p>\n\n\n\n Calcium nitrate from this? Fertiliser boosts plant calcium and nitrogen. Eggshell waste is recycled industrially.<\/p>\n\n\n\n Caveats:<\/strong> use dilute acid; conc HNO\u2083 is violent, brown NOx gases. JEE practicals stress dilution.<\/p>\n\n\n\n Eco angle: ocean acidification dissolves shells like this, harming marine life. Ties to current affairs MCQs.<\/p>\n\n\n\n Wear goggles and gloves; acid splashes burn. Do in a fume hood if conc. Neutralise waste with base.<\/p>\n\n\n\n Hack:<\/strong> Crush the shell fine for faster reaction. Test CO\u2082 with a burning splint? No, but limewater, yes.<\/p>\n\n\n\n For home demo, vinegar on the shell is safer, same idea minus nitrate.<\/p>\n\n JEE Exam Relevance Deep Dive<\/h2>\n\n\n\n
CaCO3\u200b(s)+2H+(aq)\u2192Ca2+(aq)+CO2\u200b(g)+H2\u200bO(l)
<\/p>\n\n\n\nReal-World Ties for Better Recall<\/h2>\n\n\n\n
Safety and Lab Hacks<\/h2>\n\n\n\n