Chemical effects of Electric Ecurrent

Distilled water is pure H2O with no dissolved salts, hence no free ions. Tap water contains dissolved minerals like calcium and magnesium salts that dissociate into ions, making it conductive.

LED is a diode that allows current only in one direction (forward bias). Reversing the polarity blocks current flow, so it does not glow. It may get damaged if voltage is high.

The cathode is negatively charged, so it attracts positively charged copper ions (Cu2+) from the copper sulphate solution, which then deposit on the key.

The cathode is the negative electrode, so it attracts positively charged ions (cations). The anode is positive and attracts negative ions (anions).

Pure water has very few ions. Adding an acid (like H2SO4) or a base (like NaOH) increases ion concentration, making water conductive enough for electrolysis.

According to Faraday’s laws, the mass of metal deposited is directly proportional to the current (amperes) and the time (seconds) for which it flows.

For silver electroplating, the electrolyte must contain silver ions. Silver nitrate (AgNO3) is commonly used because it dissociates into Ag+ and NO3- ions.

A bulb’s filament needs to become red-hot (around 1000°C) to emit light, requiring strong current. An LED emits light by electron-hole recombination at low current.

Heating of wire is a heating effect, not a chemical effect. Chemical effects involve decomposition, deposition, or colour change due to chemical reactions.

Copper atoms from the anode lose electrons (oxidation) and go into the solution as Cu2+ ions, replenishing the electrolyte. The anode gradually dissolves.

Zinc is more reactive than iron. It acts as a sacrificial anode: even if the coating is scratched, zinc corrodes first, protecting the iron from rust.

The electrolyte contains metal ions that migrate to the cathode. It also allows ionic conduction, completing the electrical circuit.

In copper electroplating, copper from the anode dissolves into the solution at the same rate as copper deposits on the cathode, keeping the Cu2+ ion concentration and blue colour constant.

Distilled water is a poor conductor due to lack of ions. Adding salt (NaCl) introduces Na+ and Cl- ions, making it a good conductor. Oil and petrol remain insulators.

LEDs have very low internal resistance. Without a resistor, a high current can flow, overheating and destroying the LED. A resistor limits current to a safe value.

At the cathode (negative electrode), hydrogen ions (H+) gain electrons to form hydrogen gas (H2). Oxygen is formed at the anode.

Tin plating on food cans prevents rusting and avoids food contamination. While it may look shiny, the primary purpose is functional (protection and food safety).

A dim glow indicates some current is flowing, but resistance is high. The liquid has few ions (e.g., weak electrolyte like tap water), so it is a poor but not zero conductor.

Electroplating requires the object to be conductive to attract metal ions. Plastic is an insulator. It must first be coated with a conductive layer (e.g., graphite paint) before electroplating.

If the object is made the anode (positive), metal atoms from the object will lose electrons and go into the solution as ions, causing the object to dissolve instead of getting plated.

Solid NaCl has ions held in a rigid lattice that cannot move. When melted or dissolved in water, the ions become free to move, making it a good conductor.

A bulb requires a minimum current to heat the filament (typically > 100 mA). An LED glows at much lower currents (1-10 mA), making the tester more sensitive.

Without stirring, the concentration of copper ions near the cathode decreases, leading to uneven or slow deposition. Stirring maintains uniform ion concentration.

Graphite is a non-metal but a good conductor of electricity. It is commonly used as an inert electrode in electrolysis because it does not react with many electrolytes.

For nickel electroplating, the anode must be made of nickel so that it dissolves and provides Ni2+ ions to the solution, maintaining concentration.

Pure water has very low conductivity. Dilute sulphuric acid provides H+ and SO4^2- ions, allowing sufficient current to flow for decomposition of water.

Chromium is very hard, corrosion-resistant, and has a brilliant shine. It is used for decorative and wear-resistant coatings (e.g., car bumpers, taps).

Salt water (high ion concentration) gives bright glow. Tap water (low ion concentration) gives dim glow. Distilled water (no ions) gives no glow.

Electroplating usually makes the surface less reactive (more corrosion-resistant). It does not increase reactivity; that would be undesirable.

Cu from anode -> Cu2+ (dissolves) and Cu2+ from solution -> Cu (deposits on cathode). The concentration of Cu2+ ions remains constant, so blue colour persists.

Without a resistor, the LED will try to draw a very high current (since its resistance is low), exceeding its rating and burning it out.

Iron is cheap but rusts. Tin is more expensive but used as a thin coating. This is cheaper than making the entire object from stainless steel or tin.

Mass is conserved. The metal deposited on the cathode comes from the anode dissolving. So anode loses exactly the same mass as cathode gains.

Graphite does not participate in chemical reactions in many electrolytes, making it an inert electrode. It also conducts electricity well.

Salt (NaCl) is a strong electrolyte that completely dissociates into Na+ and Cl- ions, giving high conductivity. Vinegar (weak acid) dissociates partially.

Copper is more reactive than silver. Copper atoms from the key can lose electrons and go into solution as blue Cu2+ ions, contaminating the silver nitrate solution.

Any dirt, oil, or oxide layer prevents the plated metal from bonding strongly, leading to peeling or uneven coating.

From 2H2O -> 2H2 + O2, two volumes of hydrogen are produced for every one volume of oxygen (at same temperature and pressure).

Aluminium foil is made by rolling pure aluminium, not by electroplating. The other options are all electroplated coatings.

The net reaction is Cu(anode) -> Cu(cathode). No H+ or OH- ions are consumed or produced, so the pH remains unchanged.

Sweat and tap water contain dissolved salts that make them good conductors. Wet hands provide an easy path for current to flow through the body.

Even if the liquid conducts, the LED has polarity. If the longer lead (anode) is not connected to positive, the LED will not glow.

Zinc is more reactive than iron. In marine environments, zinc blocks (sacrificial anodes) are attached to ships. Zinc corrodes instead of the iron hull.

High current density causes rapid deposition, leading to uneven, granular, or burnt-looking deposits instead of a smooth, shiny layer.

Rainwater absorbs carbon dioxide from air, forming carbonic acid (H2CO3) which dissociates into H+ and HCO3- ions, making it slightly conductive.

For gold plating, the electrolyte must contain gold ions (Au+ or Au3+). Gold chloride (AuCl3) or gold cyanide (KAu(CN)2) solutions are used.

Cyanide complexes help control the release of metal ions, giving fine-grained, shiny deposits. Safer alternatives are now being developed.

Without ions in the water, no current flows. Therefore, no metal deposition (electroplating) can take place.

Faraday’s First Law states that the mass deposited is proportional to the quantity of electric charge (current x time) passed through the electrolyte.

At high frequencies, current flows near the surface (skin effect). Silver has the lowest electrical resistivity of all metals, so a silver coating reduces signal loss