Chapter 3: Thermochemistry

A reaction is performed in a beaker with a temperature probe recording the temperature changes of the reaction. If the temperature began at 15.0 degrees Celsius and ended at 27.5 degrees Celsius. What type of reaction is this?

• Exothermic

• Endothermic

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

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?

Formula = heat energy of reactants - heat energy of products

• +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. Th 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

Which are the following pairs of acid and alkali will produce the lowest temperature change when mixed together? (All the acids and alkalies have the same concerntration of 1.0 mol dm^-3)

• 100 cm³ of HCl and 25 cm³ of NaOH

• 100 cm³ of H₂SO₄ and 25 cm³ of NaOH

• 100 cm³ of HNO₃ and 25 cm³ of NaOH

• 100 cm³ of CH₃COOH and 25 cm³ of NaOH