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Grade 11 Chemistry Knowledge Summary 1: Chemical Production and Equilibrium | Brief Solutions
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I-1.1 Ammonia-synthesis equation, entropy sign and spontaneous-temperature regime. Show answer
$\mathrm{N_2+3H_2\rightleftharpoons2NH_3}$ (high temperature and pressure, iron catalyst); $\Delta S<0$; spontaneous at low temperature.
I-1.2 Pressure effects and industrial operating pressure. Show answer
Reaction rate; shifts forward; typically about $10\sim30\ \mathrm{MPa}$, varying by process.
I-1.3 Temperature effects on rate and equilibrium, and operating temperature. Show answer
High temperature; low temperature; about $500^\circ\mathrm C$.
I-1.4 Catalyst, poisons, rate-limiting step, feed treatment and hydrogen-to-nitrogen ratio. Show answer
Iron catalyst; $\mathrm{H_2S}$ and $\mathrm{CO}$; poisoning; rate-limiting step; purification; $2.8\sim2.9$.
I-1.5 Concentration changes and ammonia separation. Show answer
Increase; decrease; liquefy; condensation.
I-2.1 Three main stages of industrial ammonia synthesis. Show answer
Feed-gas production, purification, synthesis.
I-2.2 Two main reactions for hydrogen production from natural gas. Show answer
$\mathrm{CH_4+H_2O\rightleftharpoons CO+3H_2}$; $\mathrm{CO+H_2O\rightleftharpoons CO_2+H_2}$ (heat and catalysts).
I-2.3 Equipment that uses reaction heat to preheat the feed. Show answer
II-1.1 Sulfuric-acid gas-production stage: equipment, reactions and purpose of crushing ore. Show answer
Gas production; fluidized-bed furnace; $\mathrm{4FeS_2+11O_2\xrightarrow{heat}2Fe_2O_3+8SO_2}$; $\mathrm{S+O_2\xrightarrow{ignition}SO_2}$; greater contact area speeds and improves reaction completion.
II-1.2 Conversion stage: equipment, reaction, heat effect, catalyst and outlet gases. Show answer
Conversion; converter; $\mathrm{2SO_2+O_2\rightleftharpoons2SO_3}$; exothermic; heat exchanger; $\mathrm{V_2O_5}$; about $450\sim475^\circ\mathrm C$; $\mathrm{O_2,SO_2,SO_3}$.
II-1.3 Absorption stage: equipment, reaction and why water is not used directly. Show answer
Absorption; absorption tower; $\mathrm{SO_3+H_2O\longrightarrow H_2SO_4}$; acid-mist formation; about $98.3\%$ sulfuric acid.
II-2.1 Reagents and equations for ammonia absorption and acid recovery of sulfur dioxide. Show answer
Aqueous ammonia; sulfuric acid. $\mathrm{SO_2+2NH_3+H_2O\to(NH_4)_2SO_3}$; $\mathrm{SO_2+(NH_4)_2SO_3+H_2O\to2NH_4HSO_3}$; $\mathrm{2NH_4HSO_3+H_2SO_4\to(NH_4)_2SO_4+2SO_2\uparrow+2H_2O}$.
II-2.2 Formula of iron red. Show answer
III-1.1 Industrial ammonia is separated by dissolving it in water. Show answer
III-1.2 $500^\circ\mathrm C$ both speeds ammonia synthesis and shifts its equilibrium forward. Show answer
III-1.3 Recycling gas after ammonia separation improves feed utilization. Show answer
III-1.4 Iron lowers activation energy and increases equilibrium conversion. Show answer
III-1.5 A hydrogen-to-nitrogen ratio slightly below $3$ relates to rate-limiting nitrogen adsorption and activation. Show answer
III-1.6 Gas from methane reforming can enter the synthesis tower without purification. Show answer
III-1.7 Gas from the roasting furnace can enter the converter directly. Show answer
III-1.8 Use cold water to absorb sulfur trioxide. Show answer
III-1.9 Converter outlet gas contains only sulfur trioxide. Show answer
III-1.10 Atmospheric-pressure sulfuric-acid production balances equilibrium and cost. Show answer
III-2 Compare rates at A and B and find hydrogen conversion at $250^\circ\mathrm C,10^4$ kPa. Show answer
III-3.1 Identify the catalyst giving the greatest activation energy from initial decomposition rates. Show answer
III-3.2 At constant volume, initially $2$ mol ammonia at $4$ MPa decomposes by $50\%$. Find $K_p$. Show answer
$K_p=27/4=6.75\ \mathrm{MPa^2}$
IV-1 Formula of green vitriol. Show answer
$\mathrm{FeSO_4\cdot7H_2O}$
IV-2 Elements oxidized during pyrite roasting. Show answer
IV-3 Balance the ionic equation for pyrite reducing iron(III). Show answer
$\mathrm{14Fe^{3+}+FeS_2+8H_2O\to15Fe^{2+}+2SO_4^{2-}+16H^+}$
IV-5 How is iron detected after dissolving the yellow precipitate? Show answer
Add KSCN solution; a blood-red color confirms iron(III).
IV-6 Explain formation of yellow $\mathrm{Fe(OH)SO_4}$ with an ionic equation. Show answer
$\mathrm{4Fe^{2+}+O_2+2H_2O+4SO_4^{2-}\to4Fe(OH)SO_4\downarrow}$
IV-7 Mass needed when preparing $200$ mL of $0.010$ mol/L potassium dichromate. Show answer
$0.735\ \mathrm g$ when preparing with a standard $250$ mL volumetric flask.
IV-8 Which additional glassware is required? Show answer
A $250$ mL volumetric flask and a glass stirring rod.
IV-9 A $w$ g sample consumes $v$ mL of $0.010$ mol/L dichromate. Find the iron(II) mass fraction. Show answer
$\dfrac{3.36\times10^{-3}v}{w}$
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