ATI TEAS 7 I Complete Chemistry Review Part 2 I

In a chemical reaction, there are reactants and products. Many reactions are reversible, indicated by a double arrow, where the forward reaction forms the product and the reverse reaction reforms the reactant. Chemical equilibrium occurs when the rate of the forward reaction equals the rate of the reverse reaction, and the ratio of products to reactants remains constant. This balance can be visualized like a seesaw. Le Chatelier's principle states that if an external stress is applied to a system at equilibrium, the system adjusts to maintain equilibrium. Factors affecting equilibrium include heat, pressure, volume, and concentration.

Le Chatelier's principle helps predict how a system at equilibrium responds to changes. Increasing the concentration of a reactant shifts the equilibrium to produce more products, while decreasing it shifts it to produce more reactants. Solids and liquids don't affect equilibrium, but gases do. Heat changes affect equilibrium differently in endothermic and exothermic reactions. Adding heat to an endothermic reaction shifts equilibrium to produce more products, while adding heat to an exothermic reaction shifts it to produce more reactants. Pressure and volume changes only affect systems with gases; increasing pressure shifts equilibrium to the side with fewer moles of gas.

Changes in pressure and volume significantly affect systems with gases. Increasing pressure shifts equilibrium to the side with fewer moles of gas, while decreasing pressure shifts it to the side with more moles of gas. Understanding this relationship helps predict the system's behavior under different conditions. For example, increasing pressure in a system with one mole of gas on the reactant side and two moles on the product side shifts equilibrium towards the reactants. Conversely, decreasing pressure shifts it towards the products. This dynamic balance ensures the system maintains equilibrium.

Reaction rate refers to the change in concentration of reactants and products over time. For a reaction to occur, molecules must collide with enough energy (greater than the activation energy) and at the correct site. Lower activation energy speeds up the reaction, while higher activation energy slows it down. Factors affecting reaction rates include temperature, concentration, surface area, and catalysts. Increasing temperature or concentration accelerates reactions by increasing collision frequency and energy. Surface area increases collisions in solids, and catalysts lower activation energy, speeding up reactions without being consumed.

A mole represents the quantity of 6.022 x 10^23 particles, known as Avogadro's number. This concept simplifies working with large numbers of atoms and molecules. For instance, one mole of carbon equals 6.022 x 10^23 carbon atoms. Molar mass, measured in grams per mole, indicates the weight of one mole of a substance. Each element's molar mass varies, reflecting differences in atomic mass. This relationship between moles, mass, and number of atoms helps calculate quantities in chemical reactions and understand the scale of atomic-level interactions.

Molar mass is the weight of one mole of a substance in grams, while molecular mass is the sum of atomic masses in a molecule. To find molecular mass, add the atomic masses of each element in the compound. For example, glucose's molecular mass involves summing the masses of carbon, hydrogen, and oxygen atoms. Accurate calculations require considering significant figures. Understanding these concepts is crucial for quantifying substances and predicting reaction outcomes. Practice problems help reinforce this knowledge by applying it to various compounds and scenarios.

Molecular mass is the sum of atomic masses of all atoms in a molecule. For example, the molecular mass of glucose involves adding the atomic masses of six carbon atoms, twelve hydrogen atoms, and six oxygen atoms. This calculation helps determine the weight of a given number of molecules, essential for stoichiometric calculations in chemical reactions. Understanding how to find molecular mass aids in predicting how much of a substance is needed or produced in a reaction, ensuring accurate measurements and efficient chemical processes.

Density is calculated as mass divided by volume. Knowing the density of a substance helps determine its mass or volume in different contexts. For instance, finding the density of a cake involves dividing its mass by its volume. Practice problems illustrate this concept, reinforcing the relationship between mass, volume, and density. This knowledge is crucial in various scientific and real-world applications, from determining the purity of a material to calculating the displacement of water by an object.

Balancing chemical equations ensures the number of atoms of each element is the same on both sides of the equation. This reflects the law of conservation of mass. Coefficients in a balanced equation represent the number of moles of each substance involved. Understanding this concept helps predict the quantities of reactants needed and products formed in a reaction. Practice problems reinforce the skill of balancing equations, crucial for accurately describing chemical reactions and their outcomes.