CHAPTER 4 THERMOCHEMISTRY

1. Which of the following is not an exothermic reaction?

Antara yang berikut, yang manakah bukan tindak balas eksotermik?

• The formation of a carbohydrate and oxygen from carbon dioxide and water.

  Pembentukan karbohidrat dan oksigen daripada karbon dioksida dan air.

• The combustion of octane in the air.

  Pembakaran oktana di dalam udara.

• The addition of water to anhydrous copper (II) sulphate.

  Penambahan air kepada kuprum (II) sulfat kontang.

• The oxidation of magnesium ribbon.

  Pengoksidaan pita magnesium.

1. The energy profile diagram represents an endothermic reaction.

Gambarajah profil tenaga mewakili satu tindak balas endotermik.

Which of the following A, B, C and D, represents the heat change?

Antara A, B, C dan D yang manakah menunjukkan perubahan tenaga?

• A

• B

• C

• D

When concentrated sulphuric acid dissolves in a beaker of water, the beaker gets hot. This is due to

Apabila asid sulfurik pekat dilarutkan dalam satu bikar air, bikar menjadi panas. Hal ini adalah disebabkan oleh

• water releases heat energy

  air membebaskan tenaga haba

• the heat is absorbed from the surroundings

  haba telah diserap dari persekitaran

• the heat is released to the surrounding

  haba telah dibebaskan ke persekitaran

• energy is used to break the chemical bonds

  tenaga digunakan untuk memecahkan ikatan kimia

The chemicals in cold packs react to absorb heat. Which of the following substances is used in cold packs?

Bahan kimia dalam pek sejuk bertindak balas untuk menyerap haba. Antara bahan yang berikut, yang manakah digunakan dalam pek sejuk?

• Sodium chloride

  Natrium klorida

• Calcium carbonate

  Kalsium karbonat

• Ammonium nitrate

  Ammonium nitrat

• Potassium sulphate

  Kalium sulfat

Which of the following is true of an exothermic reaction?

Antara berikut, yang manakah benar tentang tindak balas eksotermik?

• The container becomes hotter.

  Bekas itu menjadi panas.

• The temperature of the mixture decreases.

  Suhu campuran tindak balas menurun.

• Heat energy is absorbed from the surroundings.

  Tenaga haba diserap dari persekitaran.

• The heat energy is converted to kinetic energy.

  Tenaga haba ditukar kepada tenaga kinetik.

Diagram shows the energy level diagram for the decomposition of calcium carbonate.

Rajah menunjukkan gambar rajah aras tenaga bagi penguraian kalsium karbonat.

Which statement can be deduced from the Diagram?

Pernyataan manakah yang boleh dirumuskan daripada Rajah?

• Heat is absorbed in the reaction

  Haba diserap dalam tindak balas tersebut

• The reaction is exothermic

  Tindak balas tersebut adalah eksotermik

• Total energy of the reactant and the products is 570 kJ

  Jumlah tenaga bagi bahan tindak balas dan hasil tindak balas adalah 570 kJ

• The reactant has more energy than the products

  Bahan tindak balas mempunyai lebih tenaga daripada hasil tindak balas

The reaction between hydrochloric acid and sodium hydroxide is an exothermic

reaction. The heat of reaction is -57 kJ mol ⁻¹ .

Which of the following energy level diagrams represents the reaction?

Tindak balas antara asid hidroklorik dengan natrium hidroksida adalah tindak balas

eksotermik. Haba tindak balas adalah -57 kJ mol ⁻¹ .

Antara gambar rajah aras tenaga berikut yang manakah mewakili tindak balas itu?

• 
• 
• 
• 

The thermochemical equation represents the reaction between aluminium and copper(II) sulphate solution.

Persamaan termokimia mewakili tindak balas antara aluminium dan larutan kuprum(II) sulfat.

2Al + 3CuSO₄ → Al₂(SO₄)₃ + 3Cu ΔH = - 42 kJ mol^-1

What is the temperature change when excess aluminium powder is added to 50 cm³ of 0.5 mol dm^-3 copper(II) sulphate solution in a polystyrene cup?

[Specific heat capacity of water = 4.2 Jg^-1 C^-1 ; Density of water = 1.0 g cm^-3]

Berapakah perubahan suhu apabila serbuk aluminium berlebihan ditambah kepada 50 cm³ larutan kuprum(II) sulfat 0.5 mol dm^-3?

[Muatan haba tentu air = 4.2 Jg^-1 C^-1 ; Ketumpatan air = 1.0 g cm^-3]

• 2 ^oC

• 3 ^oC

• 5 ^oC

• 6 ^oC

The following equation represents the reaction between hydrogen and chlorine.

Persamaan berikut mewakili tindak balas antara hidrogen dan klorin.

H2 (g) + Cl2 (g) → 2HCl (g)

Table shows the energy content for some chemical bonds.

Jadual menunjukkan kandungan tenaga bagi beberapa ikatan kimia.

What is the heat of the reaction?

Berapakah haba tindak balas?

• +184 kJ mol^-1

• -184 kJ mol^-1

• +1046 kJ mol^-1

• -1046 kJ mol^-1

In an experiment , 2 g of magnesium powder is added to 50 cm³ of 0.2 mol dm^-3 zinc sulphate

solution. The temperature of the mixture increases by 12 °C. What is the heat of displacement

in the experiment?

[Specific heat capacity of a solution = 4.2 J g ^{– 1} °C ^{– 1} ; Relative atomic mass of Mg = 24]

Dalam satu eksperimen, 2 g serbuk magnesium ditambahkan kepada 50 cm³ larutan zink sulfat 0.2 mol dm ^{– 3}. Suhu campuran meningkat sebanyak 12 °C. Berapakah haba penyesaran dalam eksperimen ini?

[Muatan haba tentu larutan = 4.2 J g ^{– 1} °C ^{– 1}, Jisim atom relatif Mg = 24]

• – 5.04 kJ mol^-1

• – 10.08 kJ mol^-1

• – 252 kJ mol^-1

• – 320 kJ mol^-1