IB myp 4-5 Chemistry – Practice Questions- All Topics
Topic :Bonding-Chemical Reactions
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 (12 marks)
Chemical changes take place when food is cooked. The video below gives some information about the chemical changes happening when eggs are cooked.
Video Script:
When food is cooked there can be a change in color, state or even a gas produced, all of which are indicators that a chemical change has taken place. The bonds in the food are broken and new bonds are formed resulting in a chemical change. The chemical change is easily seen when we cook an egg. The egg white will change from colorless to white as heat is added and the egg white changes from water-soluble to insoluble when it has cooked. Chemically, the proteins have become altered and new chemical bonds have formed.
Another way to cook an egg is to place it, in its shell, in boiling water. This is called boiling an egg. People like to cook their eggs for different lengths of time based on their personal choice.
Question a (4 marks)
A student investigated how egg appearance changes with cooking time (0-15 minutes). Identify:
▶️Variables Identification
Independent variable: Cooking time (minutes)
Dependent variable: Egg appearance/texture (qualitative) or solubility (quantitative)
Control variables:
- Egg size/type
- Water temperature
- Starting egg temperature
- Container size/material
Explanation: The investigation examines how cooking duration affects protein denaturation in eggs, with other factors kept constant.
Question b (3 marks)
Suggest a suitable hypothesis for this investigation:
▶️Hypothesis Structure
If: Cooking time increases
Then: The egg white will become more opaque and firm
Because: Heat causes protein denaturation and coagulation through breaking of hydrogen bonds and formation of new bonds between protein strands
Alternative: Longer cooking times will result in less soluble egg proteins due to permanent structural changes in the protein molecules.
Question c (3 marks)
Bread contains sugars and proteins. When toasted, it undergoes the Maillard reaction:
Maillard Reaction:
▶️Answer/Explanation
Answer: Bread turns brown when toasted due to the Maillard reaction – a chemical reaction between reducing sugars and amino acids in proteins at high temperatures (140-165°C), producing new flavor compounds and brown melanoidins.
Key Points:
- Non-enzymatic browning reaction
- Requires both sugars and proteins
- Produces characteristic toast flavor and color
- Different from caramelization (sugar-only reaction)
Question d (2 marks)
Predict how toast appearance would differ if heated at lower temperature for the same time:
▶️Answer/Explanation
Prediction: The toast would be lighter in color (less browning)
Justification: The Maillard reaction is temperature-dependent – lower temperatures provide insufficient activation energy for the reaction to proceed at the same rate, resulting in less color and flavor development.
Alternative: Might show uneven browning if temperature is below the reaction threshold in some areas.
Question:
Calculate the amount (in moles) in each of the following masses:
a) 4.00 g of sodium hydroxide NaOH (Mr = 40.00 g mol−1)
b) 58.80 g of sulfuric acid H2SO4 (Mr = 98.09 g mol−1)
c) 14.6 g of hydrogen chloride HCl (calculate Mr)*
d) 58.8 g of nitric acid HNO3 (calculate Mr).*
*Use the values of Ar on the periodic table.
▶️Answer/Explanation
Ans: a) moles = mass (g) / molar mass (g mol–1)
= 4.00 / 40.00 = 0.100 mol
b) 58.80 / 98.09 = 0.5994 mol
c) 14.6 / 36.5 = 0.400 mol
d) 58.8 / 63.02 = 0.933 mol