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Calculate H of a reaction as Σbonds broken − Σbonds formed Grade 10 SABIS ​ Calculating ΔH (enthalpy change) of a reaction using the sum of bonds broken minus the sum of bonds formed is a fundamental concept in thermochemistry. This method is based on the idea that the enthalpy change of a reaction is determined by the energy required to break the existing bonds in the reactants and the energy released when new bonds are formed in the products. To calculate ΔH using this approach, we start by identifying the bonds present in the reactants and the products. Each bond is associated with a specific bond energy, which represents the energy required to break that bond. The sum of bonds broken refers to the total energy required to break all the bonds in the reactants. This is determined by adding up the bond energies of all the bonds in the reactant molecules. Similarly, the sum of bonds formed refers to the total energy released when new bonds are formed in the products. This is determined by adding up the bond energies of all the bonds in the product molecules. Once the bond energies for the bonds broken and formed are determined, we subtract the sum of the bond energies of the bonds formed from the sum of the bond energies of the bonds broken. The resulting value represents the enthalpy change of the reaction, ΔH. For example, let's consider the combustion of methane (CH4) to form carbon dioxide (CO2) and water (H2O). We know the bond energies for the C-H, C=O, and O-H bonds involved in this reaction. By subtracting the sum of the bond energies for the bonds formed (C=O and O-H) from the sum of the bond energies for the bonds broken (C-H), we can calculate the enthalpy change, ΔH, for this reaction. It's important to note that the bond energies used in these calculations are typically average values and can vary depending on the specific molecular environment and conditions. Additionally, bond energy calculations assume that all bonds in a molecule have equal energy, neglecting any effects of neighboring atoms or functional groups. Calculating ΔH as the sum of bonds broken minus the sum of bonds formed provides a valuable approach to estimate the enthalpy change of a reaction without relying on direct experimental measurements. It allows us to understand the energy changes associated with the breaking and forming of chemical bonds during a reaction. In summary, calculating ΔH of a reaction as the sum of bonds broken minus the sum of bonds formed involves determining the bond energies for the bonds broken and formed in the reactants and products. By subtracting the sum of the bond energies for the bonds formed from the sum of the bond energies for the bonds broken, we can calculate the enthalpy change of the reaction. This approach provides insights into the energy transformations occurring in chemical reactions and aids in understanding the thermodynamic behavior of systems.

Boiling an egg in boiling water for two minutes, then cooling the water Grade 10 SABIS SABIS Chemical

Potential energy diagram of an exothermic reaction Grade 10 SABIS ​

Observations for the reaction of alkali metal hydride with water: Grade 10 SABIS ​ Evolution of a gas that burns with a squeaky pop sound with a lit splint.

Generally, reactions with high activation energy tend to be slow. Grade 10 SABIS ​

Stoichiometric Calculations with Limiting Reagent Grade 10 SABIS SABIS Solve stoichiometric calculation questions involving a limiting reagent

Plateau ​ ​ The flat horizontal section on a heating or cooling curve that represents a phase change occurring at a constant temperature.

Hess’s Law Definition Grade 10 SABIS ​ 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.

Filtrate ​ ​ The liquid that passes through the filter paper during the filtration process.

< Back Atomic Structure Lesson 4 ⚛️ Lesson 4 ⚛️ Explore the world of atomic and ionic radii in this visually enhanced quiz. Discover the patterns of atomic size across the Periodic Table and the changes in ionic radius when atoms gain or lose electrons. Unveil the secrets of the microcosm, one atom at a time! Previous Next ⚛️ 1.1.4 Atomic & Ionic Radius ⚛️ 💥🔬 Navigating the Universe of Atoms: Atomic & Ionic Radii 🔬💥 🌌 Measuring Atomic Size: Atomic Radius 🌌 When we think of the atomic radius, we're actually measuring the size of an atom. 📏 But how? Imagine taking two atoms of the same type, say two hydrogen atoms, bonding them together, and then measuring the distance between their nuclei. 📍📍 The atomic radius is half of this distance. 🧪 But atoms are not all the same size! Just like cities across a country, they show trends across the Periodic Table. 🗺️💡 📉 As you travel across each Period (left to right), atomic radii generally decrease. Why? Well, as you move across, the atomic number increases—meaning more protons. More protons = stronger pull on electrons = smaller atoms. 🔄 📈 On the other hand, as you journey down each Group (top to bottom), atomic radii generally increase. Here, we have more electron shells, which "shield" outermost electrons from the pull of the nucleus—leading to bigger atoms! 🔄 And what about that big jump in size between a noble gas at the end of a period and the alkali metal at the beginning of the next? It's all about the extra shell! More shells = more shielding = larger atomic radius! 💥 🌠 Examining Ion Sizes: Ionic Radius 🌠 The ionic radius, on the other hand, measures the size of an ion—a charged atom. Just like atomic radius, ionic radius also follows certain patterns! 🧩🔍 🔽 If an atom gains extra electrons to become a negatively charged ion (anion), its ionic radius increases. Why? The extra electrons are further from the nucleus and are loosely held, which increases the size. 🔄 🔼 If an atom loses electrons to become a positively charged ion (cation), its ionic radius decreases. Here, the remaining electrons are pulled in tighter by the nucleus, resulting in a smaller ion. 🔄 So, atomic and ionic radii offer a sort of "map" to the universe of atoms and ions. By understanding these trends, you're not just studying chemistry—you're discovering the unseen landscape of the microcosm, one atom (or ion) at a time! 💥🌌

neutralization reaction Grade 10 SABIS SABIS Exothermic Reaction

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