Thermochemistry

What is the meaning of heat of reaction?

• The energy needed to break the chemical bond

• The energy needed to start the reaction

• The energy involved when change of state of matter happens

• The change in the energy contained in the products and in the reactants

Which of the following is correct about exothermic and endothermic reaction?

• Exothermic- Heat is absorbed, endothermic - Heat is release

• Exothermic - Chemical bond is broken, Endothermic - Chemical bond is formed

• Exothermic - Temperature of surrounding increase, Endothermic - Temperature of surrounding decrease

• Exothermic - Total energy content of product is higher than total energy content of reactant, endothermic - Total energy content of reactant is higher than total energy content of product

Diagram shows the mercury level of a thermometer in reaction.

• Endothermic reaction

• Exothermic reaction

• Bond breaking in the reaction absorbs energy

• The amount of energy in the product is higher than the reactant

Which statement is correct about exothermic reaction?

• The heat absorbed during bond breaking is more than the heat release during bond formation

• The heat absorbed during bond breaking is less the heat released during bond formation

• The heat absorbed during bond breaking is equal to the heat released during bond formation

• No heat is absorbed or released during bond breaking and formation

Which of the following absorbs heat from the surrounding?

• Adding acid to alkali

• Adding concentrated acid to water

• Dissolving solid ammonium chloride in water

• Dissolving anhydrous copper(II) sulphate in water

A pupil discovered that a water container becomes cold when a chemical is dissolved in the water. Which of the following is the chemical?

• Sulphuric acid

• Ammonium chloride

• Sodium hydroxide

• Calcium Oxide

Which process absorb energy?

• Evaporation

• Combustion

• Neutralisation

• Displacement

Which reaction is endothermic?

• Combustion

• Displacement

• Neutralisation

• Decomposition

Which of the following is an example of endothermic reaction?

• Solid sodium hydroxide dissolved in distilled water

• Solid ammonium nitrate dissolved in distilled water

• Dilute hydrochloric added to silver nitrate solution

• Dilute hydrochloric added to potassium hydroxide solution

Which of the following absorbs heat?

• Water to steam

• Liquid sulphur to solid sulphur

• Hydrogen + Nitrogen ---> ammonia

• Magnesium + Hydrochloric acid --> magnesium chloride + hydrogen