1.
Calculate :
2.
Calculate the heat quantity in - kJ - required to raise the temperature of 48.7 g of water from 22.8 C to 62 C
3.
Calculate the heat quantity in - kJ - required to raise the temperature of 48.7 g of water from 22.8 C to 62 C
4.
Which one of the following substances has the higher specific heat ? ...........
Correct Answer
A. 1 g of water
Explanation
Water has a higher specific heat compared to the other substances mentioned. This means that it requires more energy to raise the temperature of 1 gram of water by 1 degree Celsius compared to the other substances. Water's high specific heat is due to its hydrogen bonding, which allows it to absorb and retain more heat energy.
5.
If the temperature of a substance is doubled , its specific heat will be ..............
Correct Answer
B. Constant
Explanation
When the temperature of a substance is doubled, its specific heat remains constant. Specific heat is defined as the amount of heat energy required to raise the temperature of a substance by a certain amount. It is an intrinsic property of the substance and does not depend on the temperature. Therefore, doubling the temperature does not affect the specific heat of the substance.
6.
If the two bodies have the same mass , gain the same amount of heat , the raise in the temperature of the second body is double that of the first , therefore the specific heat of the second body is ............ the first one.
Correct Answer
C. Half
Explanation
If two bodies have the same mass and gain the same amount of heat, but the temperature rise of the second body is double that of the first, it means that the second body requires less heat to increase its temperature compared to the first body. This implies that the specific heat of the second body is half that of the first body.
7.
The following is a list of specific heat capacities for a few metals :
C copper = 0.385 , C iron = 0.444 , C silver = 0.240 , C aluminum = 0.900
50 g of sample on an unknown metal is heated with 800 joules , if the temperature of the metal increases by 41.6 C , What is the identity of the unknown metal ? ................
Correct Answer
A. Copper
Explanation
The specific heat capacity of a substance is the amount of heat energy required to raise the temperature of a unit mass of that substance by one degree Celsius. In this question, the unknown metal has a specific heat capacity of 0.385. The metal requires 800 joules of heat energy to increase its temperature by 41.6 degrees Celsius. By comparing the given specific heat capacities, we can see that the specific heat capacity of copper is the closest to 0.385. Therefore, the identity of the unknown metal is copper.
8.
Using the quantity of heat equation , what would the formula look like if we were calculating the change in temperature ? ........
Correct Answer
B. Qp/m.c=Δ T
Explanation
The formula for calculating the change in temperature using the quantity of heat equation is qp/m.c=Δ T. This formula represents the change in temperature (Δ T) as the quotient of the heat absorbed or released (qp), the mass of the substance (m), and the specific heat capacity (c). By dividing the heat by the product of the mass and specific heat capacity, we can determine the change in temperature.
9.
The (+ ve) sign which precedes the Δ H value , indicates that the enthalpy of products is ............ that of reactants
Correct Answer
A. Larger than
Explanation
The positive sign before the ΔH value indicates that the enthalpy of the products is larger than that of the reactants. This means that the reaction is exothermic, releasing heat to the surroundings.
10.
If the heat content of products is lower than that of reactants , thus the reaction ...........
Correct Answer
B. Is exothermic
Explanation
If the heat content of products is lower than that of reactants, it means that heat is being released or given off during the reaction. This indicates an exothermic reaction, where energy is being released to the surroundings.
11.
Dissolving process is called hydration when the solvent is ..........
Correct Answer
D. Water
Explanation
The dissolving process is called hydration when the solvent is water. This is because water has a unique ability to dissolve many substances due to its polar nature. When a solute is dissolved in water, the water molecules surround and separate the solute particles, resulting in a homogeneous mixture. In contrast, benzene, oil, and alcohol are nonpolar solvents and do not undergo hydration when dissolving solutes.
12.
In the following thermochemical equation :
The heat change accompanied with this process is called ............... heat
Correct Answer
C. Dissolving
Explanation
The heat change accompanied with the given thermochemical equation is called "dissolving" heat.
13.
What is the change in Enthalpy on dissolving 40 g of NaOH in water to form one liter of solution , knowing that the temperature raised by 10.6 C ? .............kJ/mol [ NaOH = 40 g/mol ]
Correct Answer
C. -44.308
Explanation
When NaOH dissolves in water, it undergoes an exothermic reaction, meaning it releases heat. The change in enthalpy (ΔH) is negative because energy is being released. To calculate the change in enthalpy, we can use the formula ΔH = q/m, where q is the heat released and m is the mass of the substance. In this case, the mass of NaOH is given as 40g/mol and the temperature change is 10.6°C. Since we are dissolving 40g of NaOH in one liter of solution, we can assume the specific heat capacity of water is 4.18 J/g°C. By converting the units and plugging the values into the formula, we find that the change in enthalpy is approximately -44.308 kJ/mol.
14.
Which of the following remains constant in the closed system ? .......
Correct Answer
A. Energy
Explanation
In a closed system, energy remains constant. This is because energy cannot be created or destroyed, it can only be transferred or converted from one form to another. Therefore, the total amount of energy in a closed system remains constant over time.
15.
In the reaction :
Correct Answer
C. Negative , because the reaction is exothermic
Explanation
The correct answer is "negative, because the reaction is exothermic." In an exothermic reaction, heat is released from the system to the surroundings, resulting in a decrease in the enthalpy of the system. This is represented by a negative sign in the enthalpy change (∆H) of the reaction.
16.
Anhydrous copper II chloride reacts with water to form hydrous copper II chloride , according to the equation :
Correct Answer
D. -30 kJ/ mol
Explanation
The correct answer is -30 kJ/mol. This indicates that the reaction between anhydrous copper II chloride and water is exothermic, releasing energy in the form of heat. The negative sign indicates that the reaction is releasing energy. The value of -30 kJ/mol indicates the amount of energy released per mole of the reactant.