DHS Y4 2023 Haber Process Worksheet (Answers)

DUNMAN HIGH SCHOOL DHP CHEMISTRY WORKSHEET – AMMONIA (HABER PROCESS) NAME..............................................…....( ) YEAR ............... DATE........................ Answer the following questions with reference to “Ammonia (Haber Process)” notes. 1 Draw a ‘dot-and-cross’ diagram to show the bonding in a nitrogen molecule, thus explain why nitrogen is quite unreactive. [3] Note: All electrons must be drawn since question did not state “show outer electrons only”. Explanation: A lot of energy is needed to break the very strong triple covalent bond between the atoms in the molecule before nitrogen can react. [1] Bond Bond energy (kJ/mol) N-N 167 N=N 418 N≡N 942 2 Complete the flow diagram for the manufacture of ammonia. [7] N2 (1 volume) – obtained from ………………………………..of ………… air H 2 ( …… volume) – obtained from …………....... of alkanes from crude oil Converter …….....°C ………… catalyst Equation: ...…….…..…..…………… Compressor (……… atm) Cooling Chamber Unreacted N2 and H2 gases N2, H2 N2, H2 & NH3 Liquid ammonia fractional distillation liquid 3 cracking 200 450 iron N2(g) + 3H2(g) ⇌ 2NH3(g) N N electron of N electron of another N key Hence, ammonia has a higher boiling point than nitrogen and hydrogen.

3 Suggest two reasons why less energy is needed to maintain the temperature for reaction C than for reaction B in page C2 of “Ammonia (Haber Process)” notes. [2] Reaction B: methane reacts with steam to make hydrogen. CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g) ∆H = +210 kJ Reaction C : nitrogen reacts with hydrogen to make ammonia N2(g) + 3H2(g) ⇌ 2NH3(g) ∆H = -92 kJ • The temperature required for reaction C is lower. • Reaction C is exothermic , heat released during the reaction can help to maintain the operating temperature of 450°C. 4 Using ideas related to stoichiometry and Avogadro’s Law, e xplain why the nitrogen and hydrogen are mixed in a ratio of 1:3 by volume. (N2(g) + 3H2(g) ⇌ 2NH3(g)) [1] • From the equation, 1 mole of nitrogen reacts with 3 moles of hydrogen to produce 2 moles of ammonia. • According to Avogadro’s Law, 1 volume of nitrogen will react with 3 volumes of hydrogen when the gases are under the same temperature and pressure. Some students compared by chemical formula of NH3. No of atoms of N: No of atoms of H is 1:3. Therefore, volume is 1:3. Why is this wrong? Another eg. 2CO + O2  2CO2. Why was CO and O2 reacted in a 2:1 volume ratio? Is there any way to explain in terms of chemical formula? Compare by moles of reactants, not of atoms in the chemical formula. 5 Explain why the iron catalyst is finely divided. [1] A finely divided catalyst has a large surface area , leading to a faster rate