Homework 11: All Of The Following Questions Are From Chapter

Homework 11all Of The Following Questions Are From Chapter 51 Defin

All of the following questions are from Chapter 5: 1. Define each of the following terms: a. energy b. work c. heat 2. What is kinetic energy, and what is the equation, given in Chapter 5, for kinetic energy? 3. List two different units for energy, give SI units where appropriate. 4. How is a food “Calorie” different from an energy “calorie”? 5. Restate the first law of thermodynamics in your own words. 6. (4 points) Matching: Place the letter of the correct definition on the line in front of the given term. calorimeter a. enthalpy change that accompanies a reaction endothermic b. heat capacity of one gram of a substance enthalpy c. E + PV enthalpy of reaction d. portion not singled out for study exothermic e. process in which the system absorbs heat Hess’s Law f. work involved in the compression or expansion of gas pressure-volume work g. property of a system determined by specifying the system’s condition specific heat h. ∆H for the overall reaction = sum of steps standard enthalpy change i. portion singled out for study state function j. enthalpy change when all substances are in their standard states surroundings k. process in which the system loses heat system l. device used to measure heat flow Name Limiting Reagents 2016 October 3, 4 Pre-Lab: due as you enter the laboratory class. 1. Write the formula for acetic acid, and calculate its molar mass. 2. Write the formula for sodium bicarbonate, and calculate its molar mass. 3. Write the complete, balanced molecular equation for the reaction of acetic acid and sodium bicarbonate—remembering that carbonic acid is unstable and produces carbon dioxide gas and water. 4. For the reaction of 2.00 g of acetic acid with 2.00 g of sodium bicarbonate: a. What is the total mass of the reactants? b. According to the law of conservation of mass, what should be the mass of all products formed, together with all remaining reactant(s), at the end of the reaction? c. Consistent with the balanced reaction in question 3, and the masses in question 4, what is the limiting reactant? d. Using the limiting reactant found above, calculate the mass of carbon dioxide formed during this reaction? e. How would this mass of carbon dioxide affect the final mass of the components after the reaction is complete? f. Calculate the mass of the remaining reactant and that of the lingering product(s).

Paper For Above instruction

The fundamental concepts of energy, work, and heat are central to understanding thermodynamics. Energy is broadly defined as the capacity to perform work or transfer heat and is measured in various units such as joules (J) in the SI system and calories (cal). Work refers to energy transfer resulting from a force applied over a distance, whereas heat involves the transfer of thermal energy between systems or surroundings. These definitions set the foundation for exploring the thermodynamic processes governing physical and chemical systems.

Kinetic energy is the energy an object possesses due to its motion. It is quantified by the equation KE = ½ mv², where m is the mass of the object and v is its velocity. This relationship illustrates how kinetic energy increases with the square of velocity, emphasizing its significance in both macroscopic and microscopic contexts. For example, in molecular systems, the kinetic energy correlates directly with temperature, linking microscopic motion to macroscopic thermal properties.

Energy units vary depending on application; the joule (J) is the standard SI unit, representing energy transfer or work done when a force of one newton displaces an object by one meter. In contrast, calories (cal) are traditionally used in food energy contexts; one food Calorie (kcal) equals 1000 small calories. This distinction underscores the importance of unit awareness in scientific communication and practical applications, such as nutrition and energy calculations.

The distinction between food Calories and energy calories is crucial: a food Calorie, often used in dietary contexts, represents kilocalories (kcal), whereas a calorie in physics refers to the amount of heat needed to raise the temperature of one gram of water by one degree Celsius. This difference in magnitude highlights the importance of understanding units when converting between nutritional and scientific energy measures.

The first law of thermodynamics, or the principle of conservation of energy, states that energy cannot be created or destroyed; it can only be transferred or transformed from one form to another. In simpler terms, the total energy of an isolated system remains constant, emphasizing the importance of energy accounting in chemical reactions and physical processes.

Matching questions delve into key thermodynamic concepts and definitions. A calorimeter is an instrument used to measure heat flow during chemical reactions. Enthalpy change (ΔH) describes the heat absorbed or released at constant pressure, including endothermic and exothermic processes. The enthalpy of reaction is the overall heat change, which can be calculated via Hess’s Law, stating that the total enthalpy change for a reaction is the sum of enthalpy changes for individual steps.

Pressure-volume work involves the expansion or compression of gases, describing work done during volume changes at constant pressure. Specific heat capacity of a substance indicates how much heat is needed to alter its temperature, serving as an intrinsic property. Standard enthalpy changes refer to reaction heats measured under standard conditions, providing a baseline for comparison. State functions like enthalpy depend only on initial and final states, not on the pathway. Surroundings and system interactions involve heat transfer, with system heat loss or absorption characterized accordingly. Devices like calorimeters facilitate precise heat flow measurements.

In the practical context of laboratory chemistry, determining limiting reagents involves calculating molar masses of reactants, balancing chemical reactions, and applying stoichiometry. For acetic acid (CH₃COOH), its molar mass is approximately 60.05 g/mol, calculated by summing atomic masses (C=12.01, H=1.008, O=16.00). Sodium bicarbonate (NaHCO₃) has a molar mass near 84.01 g/mol. The reaction between acetic acid and sodium bicarbonate produces carbon dioxide, water, and sodium acetate, described by the balanced equation: CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂.

When reacting 2.00 g of acetic acid and sodium bicarbonate, the total initial mass is 4.00 g. Assuming complete reaction, the total mass of products equals the sum of reactants due to conservation of mass. To identify the limiting reactant, molar quantities are compared: moles of acetic acid = 2.00 g / 60.05 g/mol ≈ 0.0333 mol; moles of sodium bicarbonate = 2.00 g / 84.01 g/mol ≈ 0.0238 mol. Since sodium bicarbonate moles are fewer, it is the limiting reagent.

Using the limiting reagent (sodium bicarbonate), the molar ratio from the balanced reaction indicates that 1 mol of NaHCO₃ produces 1 mol of CO₂. Therefore, 0.0238 mol NaHCO₃ will generate approximately 0.0238 mol CO₂. Multiplying by the molar mass of CO₂ (44.01 g/mol), the mass of CO₂ produced is approximately 1.046 g. The formation of CO₂ does not alter the total mass since gases are contained within the reaction system; thus, the remaining reactants and products' mass remains consistent with initial reactants, unless gaseous escape occurs in open systems.

Finally, the mass of unreacted acetic acid can be calculated based on the consumption of sodium bicarbonate, indicating the amounts of residual reactants and formed products, aligning with the law of conservation of mass.

References

• Atkins, P., & de Paula, J. (2010). Physical Chemistry (9th ed.). Oxford University Press.