Thermochemistry Review

The SI unit of energy is joule. Energy is defined as the ability to do work or cause a change. The joule is the unit used to measure energy in the International System of Units (SI). It is named after James Prescott Joule, a British physicist who made significant contributions to the study of energy and heat. The joule is defined as the amount of energy transferred when a force of 1 newton is applied over a distance of 1 meter. It is widely used in physics and engineering to measure various forms of energy, such as mechanical, electrical, and thermal energy.

Celsius is a unit for temperature, not heat. Heat is measured in calories, joules, and kilocalories, but Celsius is a scale used to measure temperature.

Enthalpy refers to the heat content of a system. It is a thermodynamic property that includes both the internal energy of a system and the product of its pressure and volume. Enthalpy is often used to measure heat flow in chemical reactions or phase changes. It is represented by the symbol H and is measured in units of energy, such as joules or calories.

The change in enthalpy for an exothermic process is negative, not positive. In an exothermic process, heat is released to the surroundings, resulting in a decrease in the system's enthalpy. Therefore, the correct answer is false.

When your body is warmed by an electric blanket during the winter, it is considered endothermic because the heat is being absorbed by your body from an external source (the electric blanket). Endothermic processes involve the absorption of heat or energy from the surroundings, resulting in an increase in temperature. In this case, the electric blanket transfers heat to your body, helping to warm you up.

To calculate the amount of calories required to raise the temperature of a substance, we can use the equation Q = mcΔT, where Q is the heat energy, m is the mass of the substance, c is the specific heat capacity, and ΔT is the change in temperature. In this case, the mass of water is given as 75.0 g, the specific heat capacity of water is approximately 1 cal/g°C, and the change in temperature is 50°C - 20°C = 30°C. Plugging these values into the equation, we get Q = (75.0 g)(1 cal/g°C)(30°C) = 2250 cal. Therefore, 2250 cal is the correct answer.

(heat absorbed q) = (3.6 g) (10 C) (0.0897 J/g C)

The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1 gram of the substance by 1 Kelvin. In this question, we are given the specific heat capacity of the metal (.899 Jg-1K-1) and the mass of the metal (2.00 kg). To find the amount of energy required to raise the temperature of the metal by 80 K, we can use the formula: energy = mass * specific heat capacity * change in temperature. Plugging in the given values, we get: energy = 2.00 kg * .899 Jg-1K-1 * 80 K = 143.84 kJ. Therefore, the correct answer is 143.84 kJ.

In the given equation, it is stated that 687 kJ of heat is produced when Si(s) reacts with 2Cl2(g) to form SiCl2(l). Therefore, since the question asks for the heat produced when 106 g of Cl2 react, we can determine the amount of heat produced by using stoichiometry. From the balanced equation, we can see that 1 mole of Cl2 reacts with 687 kJ of heat. We can calculate the number of moles of Cl2 in 106 g using its molar mass, and then use the mole ratio to find the heat produced. The calculation results in 513 kJ of heat produced.

Celsius is a unit for temperature, not heat. Heat is typically measured in units such as calories, joules, or kilocalories. Celsius is used to measure the temperature scale and represents the degree of hotness or coldness of an object or environment. It is not directly related to the amount of heat energy present.

The heat absorbed by the water = q= smΔT = 2100 J. Heat released from the metal is = heat gained by the water. Heat released = -q = smΔT.

The heat change for a reaction can be calculated using the equation: q = mcΔT, where q is the heat change, m is the mass of the solution, c is the specific heat capacity of water, and ΔT is the change in temperature. In this case, the mass of the solution is given as 65.0 g, and the change in temperature is 30.0C - 25.0C = 5.0C. The specific heat capacity of water is approximately 4.18 J/g°C. Using these values, we can calculate the heat change in joules: q = (65.0 g)(4.18 J/g°C)(5.0C) = 1361 J. Converting this to kJ gives 1.36 kJ, which matches the given answer.

The change in enthalpy when 2.24 mol of sodium hydrogen carbonate decomposes can be calculated using the heat of reaction. Since the heat of reaction is given as 129 kJ, and 2.24 mol of sodium hydrogen carbonate is reacting, the change in enthalpy can be calculated by multiplying the heat of reaction by the number of moles of the reactant. Therefore, the change in enthalpy is 129 kJ/mol x 2.24 mol = 289.76 kJ. However, since the question asks for the change in enthalpy, the answer should have the opposite sign, resulting in -289.76 kJ. The closest option to this value is -144 kJ, which is the correct answer.

The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1 gram of the substance by 1 Kelvin. In this question, we are given the specific heat capacity of the metal (.899 Jg-1K-1) and the mass of the metal (2.00 kg). To find the amount of energy required to raise the temperature of the metal by 80 K, we can use the formula: Energy = specific heat capacity × mass × change in temperature. Plugging in the values, we get: Energy = .899 Jg-1K-1 × 2.00 kg × 80 K = 143.84 kJ. Therefore, the correct answer is 143.84 kJ.

Certainly! Here's a simplified format:



To calculate the heat capacity of the metal:



1. For the water:

   - Mass of water (m_water) = 150.0 g

   - Specific heat capacity of water (c_water) = 4.18 J/g°C

   - Change in temperature of water (ΔT_water) = 18.3°C - 15.0°C = 3.3°C

   - Calculate Q_water = m_water * c_water * ΔT_water



2. For the metal:

   - Mass of metal (m_metal) = 150.0 g

   - Change in temperature of metal (ΔT_metal) = 75.0°C - 18.3°C = 56.7°C

   - Calculate c_metal using the equation:

     c_metal = (m_water * c_water * ΔT_water) / (m_metal * ΔT_metal)



3. Calculate c_metal:

   - c_metal ≈ 0.2286 J/g°C



So, the heat capacity of the metal is approximately 0.2286 J/g°C, which is rounded off to 0.23 J/g°C.