HESI A2 Chemistry With Complete SOLUTIONS

What makes an atom's physical structure? - ANSWER A nucleus and orbits(sometimes known as electron clouds) What composes the center of the atom? - ANSWER Protons and neutrons What spins in the orbits of an atom? - ANSWER Electrons What are the energy levels of the atom called? - ANSWER Shells or orbits What is the term used to define an atom that is electrically charged? - ANSWER Ionic state. What is a cation? - ANSWER An atom with a positive charge What is anion? - ANSWER An atom with a negative charge What is the structure of the periodic table? - ANSWER A series of rows called periods, and columns called groups. What can be predicted by the group an element occupies? - ANSWER Charge and the numbers of electrons in its outer shell. What is the name and properties of group VIII of the periodic table? - ANSWER Noble gases. They tend to remain neutral in most situations, because their outer orbits are complete. What is the atomic number? - ANSWER The number of protons in the nucleus, defines an atom of a particular element. What is the atomic mass? - ANSWER The average mass of an element's isotopes. What are isotopes? - ANSWER Different kinds of the same atom that vary in weight. What is a compound? - ANSWER The combination of different elements. What do chemical reactions resemble? - ANSWER A cooking recipe. What are the reactants in a chemical reaction? - ANSWER The ingredients of a chemical reaction. What is the term given to the results of a chemical reaction? - ANSWER The products. Why must a chemical equation be balanced at the end of a reaction? - ANSWER Because the law of conservation of mass indicates that mass cannot be created nor destroyed in a chemical reaction. What are equilibrium reactions? - ANSWER Chemical reactions that stop before all the reactants are used to make the products. What causes equilibrium? - ANSWER The state in which reactants are forming products at the same rate that products are forming reactants. What are the four basic ways to increase the reaction rate? - ANSWER Increase temperature Increase the surface area of the reactants Add a catalyst Increase the concentration of the reactants. What does increasing temperature cause in a chemical reaction? - ANSWER The particles have greater kinetic energy, increasing the speed at which they move around, and the chance of collision between particles. How does increasing the surface area of the particles in a reaction speed chemical reactions? - ANSWER Gives the Particles more opportunities to come in contact with each other. What is a catalyst? - ANSWER An agent that accelerates a chemical reaction by reducing the activation energy or the amount of energy necessary for a reaction to occur. What is the effect of increasing the concentration of reactants in a chemical reaction? - ANSWER More chance collisions occur between the reactants, producing more products. What is a solution? - ANSWER A homogeneous mixture of two or more substances. What is a solute? - ANSWER The part of a solution being dissolved. What is a solvent? - ANSWER The part of a solution the solute is being dissolved in. What are compounds? - ANSWER Mixtures of different elements to create a single matter. What are alloys? - ANSWER Solid solutions of metals to make a new one. e.g. bronze ( a mixture between copper and tin) What are Amalgams? - ANSWER A specific type of alloy in which another metal is dissolved in Mercury. What are emulsions? - ANSWER Mixtures of matter that readily separate such as water and oil. What occurs in a synthesis reaction? - ANSWER Two elements combine to form a product. What occurs in a decomposition reaction? - ANSWER Breaks a compound into its component parts. What occurs in a combustion reaction? - ANSWER An exothermic (explosive) reaction occurs. Usually initiated by heat acting on oxygen and a fuel compound such as hydrocarbon. What are the products of the combustion of hydrocarbon? - ANSWER Carbon dioxide and water. What occurs in a single replacement chemical reaction? - ANSWER An ionic compound reacts with a more active metal to create a new compound. What occurs in a double replacement compound? - ANSWER Involves two ionic compounds The positive ion from one compound combines with the negative ion from another compound. What is the result of a double replacement compound? - ANSWER Two new ionic compounds that have "switched partners" AB + XY ---> AY + XB What is chemical bonding? - ANSWER The joining of an atom, element, or chemical to another. What are the two types of chemical bonding? - ANSWER Ionic and covalent What is ionic bonding? - ANSWER An electrostatic attraction between two oppositely charged ions. I.E. a cation and an anion. Usually a metal and a nonmetal What is covalent bonding? - ANSWER When two atoms share electrons. A single covalent bond is the sharing of one pair of electrons. What is the strongest of any bond? - ANSWER The covalent bond. Generally formed by two nonmetals. What is a non-polar bond? - ANSWER When electrons are shared equally What are inter-molecular forces? - ANSWER Weaker forces of attraction between two molecules, such as: *hydrogen bonding, dipole-dipole interactions, and dispersion forces.* What are hydrogen bonds? - ANSWER The result of the attraction for a hydrogen atom by a highly electronegative element. Which elements are generally involved in hydrogen bonds? - ANSWER Fluorine (F) Oxygen (O2) Nitrogen (N) How strong are hydrogen bonds? - ANSWER Hydrogen bonds are 5-10% as strong as covalent bonds, making them the strongest of the inter-molecular forces. What are dipole-dipole interactions? - ANSWER The attraction of one dipole on one molecule for the dipole of another molecule. How is a dipole created? - ANSWER When an electron pair is shared unequally in a covalent bond between two atoms or elements. What are the charges on the ends of a dipole? - ANSWER Because electrons are shared unequally, the molecule, not the covalent bond will have a positive and a negative end or side. What are dispersion forces? - ANSWER The phenomenon that occurs when electrons within an element or a compound concentrate themselves on the end of an atom. What do dispersion forces cause? - ANSWER A momentary dipole, which could be attracted to another momentary dipole of opposite charge in another element or compound. How strong are dispersion forces? - ANSWER Dispersion forces are the weakest of all the inter-molecular forces. What is stoichiometry? - ANSWER The part of chemistry dealing with the quantities and numeric relationships of the participants in a chemical reaction. Rules for balancing chemical equations (stoichiometry) - ANSWER 1)Determine the correct formulas for all the reactants and products in the reaction. 2)Begin balancing with the most complicated-looking group. A polyatomic ion that appears unchanged on both sides of the equation can be counted as a single unit. 3)Save the elemental (single elements) reactants and products for last, especially if it is hydrogen or oxygen. 4)Keep your eye out for diatomic molecules such as oxygen, hydrogen, and the halogens. 5)If you get stuck, double the most complicated-looking group and try again. 6)Finally, make sure that all coefficients are in the lowest possible ratio. 7)No fractions! Don't mess with subscripts. What is the function of the coefficients in a chemical reaction? - ANSWER Coefficients are put in front of chemical compounds and used in a ratio to compare how much of one substance is needed to react with another in a certain reaction.