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4fcbed57-646f-42de-8635-c94b58993f6a Any reaction or process that releases heat energy Summary Exothermic

f88b943c-f7c2-40a4-afeb-a70b512d0222 The reaction that takes place when a spark is introduced to a mixture of H2 and O2 gas Summary Exothermic

STP, Volume Ratios, Energy in Reactions, and Limiting Reagents Previous All Content Next Chapter 4 SABIS Grade 10 Part 4 STP, Volume Ratios, Energy in Reactions, and Limiting Reagents ✅ Lesson 19: ✅ STP, Volume Ratios, Energy in Reactions, and Limiting Reagents Hello learners! 🌞🎒 Today's chemistry class is going to be a thrilling ride as we explore concepts like Standard Temperature and Pressure (STP), stoichiometric calculations, and limiting reagents. Buckle up and get ready! 🚀🔬💡 Prerequisite Material Quiz 📚🧠 What does STP stand for? What are the conditions for STP? True or False: At STP, 1.00 mole of any gas occupies 22.4 dm³. How much percentage of air is oxygen gas by volume? What is a limiting reagent in a chemical reaction? Can the volume ratio at STP be used for any given reaction equation? True or False: The limiting reagent determines how much of the other reactants will be consumed in a chemical reaction. Can we write an equation including the energy required or released? True or False: A limiting reagent gets completely used up in a chemical reaction. Can we solve problems using the volume ratio? (Answers at the end of the lesson) Explanation: STP, Volume Ratios, Energy in Reactions, and Limiting Reagents 🧐👩🔬 Standard Temperature and Pressure (STP) STP is a common set of conditions for gases defined as 0 degrees Celsius and 1.00 atmosphere pressure. Under these conditions, any gas will have a volume of 22.4 dm³ per mole. Volume Ratios In gas reactions at STP, the volumes of gases involved can be directly related to the coefficients in the balanced equation. These are the volume ratios. Energy in Reactions Chemical reactions either absorb or release energy. We can represent this energy change in the chemical equation. Limiting Reagents In a chemical reaction, the limiting reagent is the substance that gets completely consumed and determines the maximum amount of product that can be formed. Examples 🌍🔬🔎 STP and volume ratios : In the reaction 2H₂(g) + O₂(g) → 2H₂O(g), the volume ratio of hydrogen to oxygen to water vapor is 2:1:2. If we start with 44.8 dm³ of hydrogen gas at STP, we would expect to produce 44.8 dm³ of water vapor, assuming oxygen is not the limiting reagent. Energy in reactions : In the combustion of methane (exothermic reaction), energy is released: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g) + energy. Limiting reagents : If we react 4 moles of hydrogen gas with 1 mole of nitrogen gas according to the equation N₂(g) + 3H₂(g) → 2NH₃(g), hydrogen is the limiting reagent. It will be completely consumed and determine the maximum amount of ammonia that can be produced (2 moles). Post-lesson MCQs 📝✅ True or False: At STP, all gases have the same volume per mole. What is the volume ratio of hydrogen to oxygen in the balanced equation for the formation of water? Can energy be a product in a chemical reaction? True or False: The limiting reagent in a reaction is always the reactant with the smallest amount of moles. How do we determine the mass of the excess reagent left in a reaction? (Answers at the end of the lesson) Answers Prerequisite Material Quiz : Standard Temperature and Pressure, 0 degrees Celsius and 1.00 atmosphere pressure, True, 20%, The substance that gets completely consumed in a reaction, Yes, True, Yes, True, Yes. Post-lesson MCQs : True, 2:1, Yes, energy can be a product in exothermic reactions, False, the limiting reagent is the substance that is completely consumed in a reaction, not necessarily the one with the smallest amount of moles, By subtracting the amount of the reagent that reacted from the total amount initially present. Complete the Questions : The volume ratio at STP for a given reaction equation is directly related to the coefficients of the gases in the balanced equation. An example of an endothermic reaction is the thermal decomposition of calcium carbonate: CaCO₃(s) + energy → CaO(s) + CO₂(g). The volume of 2 moles of nitrogen gas at STP is 2 moles × 22.4 dm³/mole = 44.8 dm³. Stoichiometric calculations involve using the coefficients in a balanced equation to calculate quantities of reactants or products. It can involve mole, mass, volume, or energy ratios. The limiting reagent is determined by comparing the amount of products each reactant could produce if it were completely consumed. The reactant that produces the least amount of product is the limiting reagent.

8b0444de-050a-49a1-a0bc-d6d71f9fbad4 when to use q=mc ΔT and when to use q=CΔT Summary The equation q=mcΔT is used to calculate the heat energy (q) transferred during a process where the temperature change (ΔT) occurs in a system with a constant mass (m) and specific heat capacity (c). This equation is applicable when we have a system with a known mass and want to determine the amount of heat energy gained or lost due to a temperature change. The specific heat capacity (c) represents the amount of heat energy required to raise the temperature of one unit mass of a substance by one degree Celsius (or Kelvin). For example, let's consider heating a sample of water. The equation q=mcΔT can be used to calculate the amount of heat energy required to raise the temperature of the water by a certain amount. Here, m represents the mass of the water, c represents the specific heat capacity of water (4.18 J/g·°C), and ΔT represents the change in temperature. On the other hand, the equation q=CΔT is used to calculate the heat energy (q) transferred during a process where the temperature change (ΔT) occurs in a system with a constant heat capacity (C). Heat capacity (C) is an extensive property that represents the amount of heat energy required to raise the temperature of an entire system by one degree Celsius (or Kelvin). It depends on the mass and specific heat capacity of the substance or substances in the system. When we want to calculate the amount of heat energy gained or lost by a system as a whole, regardless of the individual masses or specific heat capacities of the components, we can use the equation q=CΔT. This equation considers the total heat capacity of the system. For instance, in a calorimetry experiment, where the heat exchange occurs between two substances in a calorimeter, we use the equation q=CΔT to determine the amount of heat gained or lost by the combined system. The heat capacity (C) in this case represents the sum of the individual heat capacities of the substances involved. It's important to note that the specific heat capacity (c) is a property specific to a substance, while the heat capacity (C) is a property of a system. The specific heat capacity is typically used when dealing with individual components, while the heat capacity is used when considering the entire system. In summary, we use the equation q=mcΔT when calculating the heat energy transferred in a process with a constant mass and specific heat capacity. On the other hand, we use the equation q=CΔT when calculating the heat energy transferred in a process with a constant heat capacity, considering the entire system. The choice between the two equations depends on whether we are focusing on individual components with known masses and specific heat capacities or the system as a whole.

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e909ac82-9389-4d10-80a9-60df914e5130 Ne, Ar, Kr, Xe and Rn can be made to react under certain conditions to give very unstable compounds. Summary

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1f66cf1e-21a5-487f-8c20-cf3762f1e827 Hess’s Law Definition Summary Hess's Law states that the total energy change in a chemical reaction is independent of the pathway taken. In simpler terms, the total energy difference between the reactants and products remains the same, regardless of the intermediate steps involved. I t's like walking from point A to point B using different routes but ending up at the same destination. To illustrate this concept, imagine you want to climb a hill. You can take a direct path or go around the hill through a longer route. Regardless of the path you choose, the total energy change of reaching the top remains the same. Similarly, let's consider the process of cooking a pizza. You can either directly bake it in the oven or prepare the dough and toppings separately before assembling and baking. The total energy change, which is the difference between the raw ingredients and the cooked pizza, remains constant. Hess's Law is based on the principle of energy conservation. It's similar to the idea that you can't create or destroy energy; you can only convert or transfer it. This law applies to all chemical reactions, allowing us to understand and calculate energy changes in a more straightforward manner. An everyday example of Hess's Law can be observed when you prepare a cup of tea. If you add sugar to hot water or separately dissolve sugar in cold water and then heat it, the total energy change due to the sugar dissolving remains the same. Another example is the construction of a Lego house. You can either build it directly from scratch or create separate sections and then assemble them. Regardless of the approach, the total energy change in constructing the complete Lego house remains constant. Hess's Law is particularly useful in cases where it's challenging to measure the energy change directly. By combining multiple reactions with known energy changes, we can calculate the energy change of the desired reaction. To further illustrate Hess's Law, let's consider the process of charging a rechargeable battery. Whether you charge it all at once or in multiple smaller sessions, the total energy change required to fully charge the battery remains the same. Similarly, think about a journey from home to a park. You might take a direct route or make detours along the way, but the total energy change of the journey, such as the fuel consumption in a car, is the same regardless of the route taken. Hess's Law allows scientists to predict and analyze energy changes in complex reactions. It simplifies calculations and provides a fundamental understanding of energy conservation in chemical systems. For instance, if we want to determine the energy change of a reaction that's difficult to measure directly, we can design a series of reactions with known energy changes. By applying Hess's Law, we can add or subtract these reactions to obtain the desired energy change. In summary, Hess's Law states that the total energy change in a chemical reaction remains constant, regardless of the specific pathway taken. This principle is similar to reaching a destination via different routes. It simplifies calculations and allows us to understand and predict energy changes in chemical reactions. Everyday examples, such as preparing tea, building Lego structures, or charging a battery, help illustrate this law in practical terms.

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< Back Unit 8 AP Chemistry Topic 1 Self Check Guide Unit 8 Self Study and Check Guide Introduction to acids and bases Unit 8: Acids & Bases More Practice This Simulation will help you create Buffer solutions correctly , add the correct combination of a weak acid with its conjugate base Try to create 5 Correct Buffer Solutions 😀 Previous Next