Precipitation Reactions — Forming Insoluble Products
31개의 반응
Precipitation reactions occur when two soluble ionic compounds react in solution to form an insoluble solid product called a precipitate. The precipitate forms because the product's lattice energy exceeds its hydration energy — the ions prefer to bond with each other rather than remain surrounded by water molecules. Solubility rules, derived from extensive experimental data, predict which combinations produce precipitates.
반응 메커니즘
When two solutions are mixed, all four possible ion combinations exist momentarily in solution. If one combination has low solubility, those ions rapidly nucleate and grow into solid crystals that settle out. The rate of precipitation depends on supersaturation, temperature, and mixing. Adding reagent slowly produces larger, purer crystals (useful in gravimetric analysis); rapid mixing produces fine precipitates. The solubility product constant (Ksp) quantifies the equilibrium between dissolved ions and solid.
일상 속 사례
Hard water stains on glass are calcium carbonate precipitated when dissolved calcium bicarbonate loses CO2. Kidney stones are precipitates of calcium oxalate or calcium phosphate that form when urine becomes supersaturated. Mixing silver nitrate with table salt (NaCl) instantly produces a white curdy precipitate of silver chloride — a reaction used in photography since the 1840s.
산업적 중요성
Wastewater treatment relies heavily on precipitation to remove phosphates, heavy metals, and fluoride. Adding lime to industrial effluent precipitates toxic metal hydroxides for safe disposal. Gravimetric analysis — precipitating, filtering, and weighing a compound — remains the gold standard for accurate quantitative determination of many analytes in regulatory testing.
Safety Note
Some precipitates contain toxic heavy metals (lead chromate, barium sulfate from barium chloride). Handle precipitates with gloves and dispose of them as chemical waste. Avoid inhaling fine precipitate dust.
수산화마그네슘 침전
MgCl₂ + 2NaOH → Mg(OH)₂↓ + 2NaCl
Magnesium chloride reacts with sodium hydroxide to form a white precipitate of magnesium hydroxide (Ksp = 5.6 × 10⁻¹²). The …
수산화알루미늄 침전
AlCl₃ + 3NaOH → Al(OH)₃↓ + 3NaCl
Aluminum chloride reacts with sodium hydroxide to form a white gelatinous precipitate of aluminum hydroxide (Ksp = 3 × 10⁻³⁴). …
이산화망가니즈 침전
MnSO₄ + 2NaOH + H₂O₂ → MnO₂↓ + Na₂SO₄ + 2H₂O
Manganese(II) sulfate is oxidized by hydrogen peroxide in basic solution to form a dark brown precipitate of manganese dioxide. Mn …
플루오린화칼슘 침전 (형석)
CaCl₂ + 2NaF → CaF₂↓ + 2NaCl
Calcium chloride reacts with sodium fluoride to precipitate calcium fluoride (Ksp = 3.5 × 10⁻¹¹). CaF₂ occurs naturally as the …
아이오딘화은 침전
AgNO₃ + KI → AgI↓ + KNO₃
Silver nitrate reacts with potassium iodide to form a yellow precipitate of silver iodide (Ksp = 8.5 × 10⁻¹⁷). AgI …
황산스트론튬 침전
SrCl₂ + Na₂SO₄ → SrSO₄↓ + 2NaCl
Strontium chloride reacts with sodium sulfate to form a white precipitate of strontium sulfate (Ksp = 3.4 × 10⁻⁷). SrSO₄ …
아이오딘화납 침전 (황금비)
Pb(NO₃)₂ + 2KI → PbI₂↓ + 2KNO₃
Lead nitrate and potassium iodide form a bright yellow precipitate of lead iodide. When the hot mixture is cooled slowly, …
브로민화은 침전
AgNO₃ + NaBr → AgBr↓ + NaNO₃
Silver bromide precipitates as a pale yellow solid with Ksp = 5.4 × 10⁻¹³. It is much less soluble than …
수산화니켈 침전
NiCl₂ + 2NaOH → Ni(OH)₂↓ + 2NaCl
Nickel chloride reacts with sodium hydroxide to form a green precipitate of nickel(II) hydroxide (Ksp = 5.5 × 10⁻¹⁶). The …
수산화아연 침전
ZnSO₄ + 2NaOH → Zn(OH)₂↓ + Na₂SO₄
Zinc sulfate reacts with sodium hydroxide to form a white gelatinous precipitate of zinc hydroxide (Ksp = 3.0 × 10⁻¹⁷). …
크로뮴산은 침전
2AgNO₃ + K₂CrO₄ → Ag₂CrO₄↓ + 2KNO₃
Silver nitrate reacts with potassium chromate to form a brick-red precipitate of silver chromate (Ksp = 1.1 × 10⁻¹²). This …
황화카드뮴 침전 (노랑)
CdCl₂ + Na₂S → CdS↓ + 2NaCl
Cadmium chloride reacts with sodium sulfide to form a bright yellow precipitate of cadmium sulfide (Ksp = 8 × 10⁻²⁷). …
탄산바륨 침전
BaCl₂ + Na₂CO₃ → BaCO₃↓ + 2NaCl
Barium chloride reacts with sodium carbonate to form a white precipitate of barium carbonate (Ksp = 2.6 × 10⁻⁹). BaCO₃ …
탄산칼슘 침전
CaCl₂ + Na₂CO₃ → CaCO₃↓ + 2NaCl
Calcium chloride reacts with sodium carbonate to precipitate calcium carbonate. CaCO₃ has a Ksp of 3.4 × 10⁻⁹. This is …
황산바륨 침전
BaCl₂ + Na₂SO₄ → BaSO₄↓ + 2NaCl
Barium chloride reacts with sodium sulfate to form an extremely insoluble white precipitate of barium sulfate (Ksp = 1.1 × …
황화구리 침전
CuSO₄ + Na₂S → CuS↓ + Na₂SO₄
Copper sulfate reacts with sodium sulfide to form a black precipitate of copper(II) sulfide (Ksp = 1.3 × 10⁻³⁶). CuS …
황화아연 침전
ZnSO₄ + Na₂S → ZnS↓ + Na₂SO₄
Zinc sulfate reacts with sodium sulfide to form a white precipitate of zinc sulfide (Ksp = 2 × 10⁻²⁵). ZnS …
황산칼슘 침전 (석고)
Ca(NO₃)₂ + Na₂SO₄ → CaSO₄↓ + 2NaNO₃
Calcium nitrate reacts with sodium sulfate to precipitate calcium sulfate (Ksp = 4.9 × 10⁻⁵). CaSO₄ is sparingly soluble, not …
인산칼슘 침전 (뼈 무기질)
3CaCl₂ + 2Na₃PO₄ → Ca₃(PO₄)₂↓ + 6NaCl
Calcium chloride reacts with trisodium phosphate to form a white precipitate of calcium phosphate (Ksp = 2.1 × 10⁻³³). Calcium …
염화납 침전
Pb(NO₃)₂ + 2NaCl → PbCl₂↓ + 2NaNO₃
Lead nitrate reacts with sodium chloride to form a white precipitate of lead chloride (Ksp = 1.7 × 10⁻⁵). PbCl₂ …
염화은 침전
AgNO₃ + NaCl → AgCl↓ + NaNO₃
Silver nitrate reacts with sodium chloride to form a white curdy precipitate of silver chloride. AgCl has a very low …
탄산납 침전
Pb(NO₃)₂ + Na₂CO₃ → PbCO₃↓ + 2NaNO₃
Lead nitrate reacts with sodium carbonate to form a white precipitate of lead carbonate (Ksp = 7.4 × 10⁻¹⁴). Basic …
황산납 침전
Pb(NO₃)₂ + Na₂SO₄ → PbSO₄↓ + 2NaNO₃
Lead nitrate reacts with sodium sulfate to form a white precipitate of lead sulfate (Ksp = 2.5 × 10⁻⁸). PbSO₄ …
옥살산 칼슘 침전 (신장 결석)
CaCl₂ + Na₂C₂O₄ → CaC₂O₄↓ + 2NaCl
Calcium chloride reacts with sodium oxalate to form a white precipitate of calcium oxalate (Ksp = 2.3 × 10⁻⁹). Calcium …
수산화코발트(II) 침전
CoCl₂ + 2NaOH → Co(OH)₂↓ + 2NaCl
Cobalt(II) chloride reacts with NaOH to form a blue or pink precipitate of cobalt(II) hydroxide (Ksp = 5.9 × 10⁻¹⁶). …
수산화구리(II) 침전
CuSO₄ + 2NaOH → Cu(OH)₂↓ + Na₂SO₄
Copper sulfate reacts with sodium hydroxide to form a pale blue gelatinous precipitate of copper(II) hydroxide (Ksp = 2.2 × …
황화수은(II) 침전 (주홍)
HgCl₂ + Na₂S → HgS↓ + 2NaCl
Mercury(II) chloride reacts with sodium sulfide to form a black precipitate of mercury(II) sulfide (Ksp = 2 × 10⁻⁵²), the …
황화철(II) 침전
FeSO₄ + Na₂S → FeS↓ + Na₂SO₄
Iron(II) sulfate reacts with sodium sulfide to form a black precipitate of iron(II) sulfide (Ksp = 6 × 10⁻¹⁸). FeS …
수산화크로뮴(III) 침전
CrCl₃ + 3NaOH → Cr(OH)₃↓ + 3NaCl
Chromium(III) chloride reacts with sodium hydroxide to form a green gelatinous precipitate of chromium(III) hydroxide (Ksp = 6.3 × 10⁻³¹). …
수산화철(III) 침전
FeCl₃ + 3NaOH → Fe(OH)₃↓ + 3NaCl
Iron(III) chloride reacts with sodium hydroxide to form a rust-brown gelatinous precipitate of iron(III) hydroxide. Fe(OH)₃ has an extremely low …
인산 철(III) 침전 (수처리)
FeCl₃ + Na₃PO₄ → FePO₄↓ + 3NaCl
Iron(III) chloride reacts with trisodium phosphate to form an insoluble yellowish-white precipitate of iron(III) phosphate (Ksp = 9.9 × 10⁻¹⁶). …