IB myp 4-5 Chemistry – Practice Questions- All Topics
Topic :Bonding-Chemical Formulas
Topic :Bonding- Weightage : 21 %
All Questions for Topic :structure and bonding,properties,chemical formulas,chemical reactions and the conservation of mass; balancing,equations, the mole concept and chemical calculations;
reaction kinetics [rates, and factors affecting rates/collision theory],equilibria/reversible reactions,energy changes in reactions, endo- and exothermicity; combustion of fuels)
Question (21 marks)
In 2015 there was an earthquake in Nepal. Many urban areas were destroyed and there was less commercial fuel available for cooking and heating.
a (2 marks) Calculate the percentage of LPG used in urban areas and the percentage of dung used in rural areas from the table.
| Type of fuel | Urban area (%) | Rural area (%) |
|---|---|---|
| Wood | 36.2 | 81.4 |
| Dung (animal waste) | 2.5 | |
| LPG | 3.9 |
▶️Answer/Explanation
Answer:
LPG urban: 41.5%
Dung rural: 9.4%
Explanation:
Calculated by subtracting all other percentages from 100% for each area. Urban total must equal 100% (36.2+2.5+3.2+0.2+15.8+0.2+0.4 = 58.5%, so LPG = 41.5%). Rural dung is given directly in the full table as 9.4%.
b (3 marks) Outline a test for carbon dioxide. Include the name of the chemical needed.
Chemical:
Test method:
Positive result:
▶️Answer/Explanation
Answer:
Chemical: Calcium hydroxide solution/limewater
Method: Bubbling through limewater
Result: Turns white/cloudy (forms CaCO3 precipitate)
Explanation:
CO2 reacts with limewater (Ca(OH)2) to form insoluble calcium carbonate (CaCO3) which makes the solution appear milky. The reaction is: CO2 + Ca(OH)2 → CaCO3 + H2O
c (11 marks) Design a safe method to determine the volume of gas produced when fuels are combusted.
Fuels to compare:
Dependent variable:2
Control variable:
Method:
Safety considerations:
▶️Answer/Explanation
Answer:
Fuels: Wood and dung (highest rural use)
Dependent: Volume of CO2 produced
Control: Mass of fuel, oxygen supply, temperature
Method: Burn fixed mass in enclosed system, collect gas in inverted measuring cylinder over water, measure volume
Safety: Use goggles, fire extinguisher, ventilated area, secure apparatus
Explanation:
Full marks require: Identification of correct fuels from table, measurable dependent variable, key controlled factors, practical collection method (e.g., gas syringe or displacement), and specific safety precautions. Higher marks for detail about repeating trials and calculating averages.
d (1 mark) State the assumption made when using this equipment to collect carbon dioxide.
▶️Answer/Explanation
Answer:
All CO2 is collected / No CO2 is lost
Explanation:
The calculation assumes 100% collection efficiency – that none of the produced CO2 escapes the collection apparatus or dissolves significantly in the water used for displacement.
e (3 marks) Comment on how smoke production could affect the validity of the results.
Smoke indicates:
Effect on results:
▶️Answer/Explanation
Answer:
1. Smoke indicates incomplete combustion
2. Less CO2 produced than theoretically possible
3. Results not valid because not all fuel fully combusted
Explanation:
Smoke consists of unburnt carbon particles, showing the combustion wasn’t complete. This means the measured CO2 volume will be lower than expected from the fuel mass, making comparisons between fuels less valid unless combustion efficiency is accounted for.
f (1 mark) Suggest an improvement to prevent smoke production.
▶️Answer/Explanation
Answer:
Increase air flow/oxygen supply
Explanation:
Smoke results from insufficient oxygen during combustion. Increasing air flow provides more oxygen, promoting complete combustion to CO2 rather than producing soot/smoke particles (incomplete combustion products).