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Identify diagram of atoms and ions from a given list. Grade 10 SABIS

Given the heats of formation calculate the heat of reaction (simple application) Grade 10 SABIS Given the heats of formation calculate the heat of reaction (simple application) Given: C(diamond) + O2(g) → CO2(g) ΔH = −395.4 kJ C(graphite) + O2(g) → CO2(g) ΔH = −393.5 kJ a) Find ΔH for the manufacture of diamond from graphite: C(graphite) → C(diamond) H = -393.5 + 395.4 = + 1.9 kJ b) Is heat absorbed or evolved as graphite is converted to diamond? Absorbed When given the heats of formation, we can calculate the heat of reaction for a specific process by applying the concept of Hess's law. Hess's law states that the overall heat of a reaction is independent of the pathway taken. This allows us to use known heats of formation to determine the heat of reaction for a desired process. Let's consider the given example of the reaction between graphite (C(graphite)) and oxygen gas (O2) to form carbon dioxide (CO2): C(graphite) + O2(g) → CO2(g) ΔH = -393.5 kJ To find the heat of reaction for the conversion of graphite to diamond, we need to compare the heats of formation of diamond (C(diamond)) and graphite (C(graphite)). By using the concept of Hess's law, we can subtract the heat of formation of graphite from the heat of formation of diamond. a) Find ΔH for the manufacture of diamond from graphite: C(graphite) → C(diamond) ΔH = -393.5 kJ + 395.4 kJ = +1.9 kJ By adding the heats of formation of the reactants and products, we find that the heat of reaction for the manufacture of diamond from graphite is +1.9 kJ. This positive value indicates that heat is absorbed during the conversion process, as the energy required to form the diamond is greater than the energy released during the formation of graphite. b) Is heat absorbed or evolved as graphite is converted to diamond? Heat is absorbed. Based on the positive value of ΔH (+1.9 kJ) for the conversion of graphite to diamond, we can conclude that heat is absorbed during this process. This means that energy is taken in from the surroundings to convert graphite into diamond. To summarize, when given the heats of formation, we can calculate the heat of reaction by applying Hess's law. In the example provided, we determined the heat of reaction for the conversion of graphite to diamond by subtracting the heats of formation of the reactants and products. The positive value of ΔH indicates that heat is absorbed during this process, indicating an energy input required for the conversion. Understanding this concept helps us analyze the energy changes and transformations that occur during chemical reactions.

Physical properties of metals: shiny, ductile (pulled into wires), malleable (hammered into thin sheets), conduct electricity. Grade 10 SABIS

Absorbing Grade 10 SABIS SABIS Taking in, as in a reaction that absorbs heat is endothermic.

Most chemical reactions proceed by sequences of steps, each involving only two-particle collisions. Grade 10 SABIS

Stoichiometric Calculations Grade 10 SABIS SABIS These calculations involve using the coefficients from a balanced chemical equation to calculate the amounts of reactants or products involved in the reaction.

Conservation of Atoms Grade 10 SABIS SABIS In chemical reactions, the number of atoms of each element in the reactants is equal to the number of atoms of the same element in the products.

Crush some salt crystals into a powder Grade 10 SABIS SABIS Physical

Variation of PE as two H atoms approach each other Grade 10 SABIS The variation of potential energy (PE) as two hydrogen atoms approach each other is influenced by the interplay between attractive and repulsive forces. As the atoms move closer together, the potential energy undergoes significant changes, which can be understood in terms of the interaction between their electron clouds and the electrostatic forces between the nuclei and electrons. When two hydrogen atoms are far apart, the electron clouds of each atom experience only weak attractive forces. At this point, the potential energy is relatively low since there is little interaction between the atoms. As the atoms start to approach each other, the electron clouds of the two atoms begin to overlap. The overlapping electron clouds create an attractive force between the atoms known as the London dispersion force. This force arises due to the temporary fluctuations in electron distribution and induces a slight attraction between the atoms. As the atoms get closer, the potential energy decreases further as the attractive forces become more significant. However, as the atoms continue to approach each other, the repulsive forces between their positively charged nuclei become more pronounced. These repulsive forces arise due to the electrostatic repulsion between the like charges of the protons in the nuclei. The potential energy starts to increase rapidly as the repulsion outweighs the attraction. At a certain point, known as the equilibrium bond length, the attractive and repulsive forces balance each other, resulting in the lowest potential energy between the two hydrogen atoms. This equilibrium bond length corresponds to the most stable configuration of the hydrogen molecule, where the potential energy is at its minimum. If the atoms are brought even closer together than the equilibrium bond length, the repulsive forces dominate, causing the potential energy to increase sharply. This indicates an unfavorable arrangement, and the atoms will experience a strong repulsion. The variation of potential energy as two hydrogen atoms approach each other can be visualized using a potential energy diagram. The diagram shows the change in potential energy as a function of the distance between the atoms, highlighting the regions of attraction, equilibrium, and repulsion. In summary, the variation of potential energy as two hydrogen atoms approach each other is determined by the balance between attractive and repulsive forces. Initially, there is a weak attraction due to electron cloud overlap, leading to a decrease in potential energy. However, as the atoms get closer, the repulsive forces between their nuclei become dominant, causing the potential energy to increase. At the equilibrium bond length, the potential energy reaches its minimum, indicating a stable configuration. Beyond this point, further approach results in a rapid increase in potential energy due to strong repulsion. Understanding the variation of potential energy provides insights into the stability and bonding behavior of hydrogen molecules.

Sublimation of iodine Grade 10 SABIS SABIS Endothermic

Cooling Curve A graphical representation of the relationship between temperature and time as a substance cools.

Rate of reaction definition SABIS Grade 10 SABIS The phrase “rate of reaction” means how fast is the reaction or the speed of the reaction.