HESI A2 Chemistry 2023 with verified questions and answers

What makes an atom's physical structure? A nucleus and orbits(sometimes known as electron clouds) What composes the center of the atom? Protons and neutrons What spins in the orbits of an atom? Electrons What are the energy levels of the atom called? Shells or orbits What is the term used to define an atom that is electrically charged? Ionic state. What is a cation? An atom with a positive charge What is anion? An atom with a negative charge What is the structure of the periodic table? A series of rows called periods, and columns called groups. What can be predicted by the group an element occupies? Charge and the numbers of electrons in its outer shell. What is the name and properties of group VIII of the periodic table? Noble gases. They tend to remain neutral in most situations, because their outer orbits are complete. What is the atomic number? The number of protons in the nucleus, defines an atom of a particular element. What is the atomic mass? The average mass of an element's isotopes. What are isotopes? Different kinds of the same atom that vary in weight. What is a compound? The combination of different elements. What do chemical reactions resemble? A cooking recipe. What are the reactants in a chemical reaction? The ingredients of a chemical reaction. What is the term given to the results of a chemical reaction? The products. Why must a chemical equation be balanced at the end of a reaction? Because the law of conservation of mass indicates that mass cannot be created nor destroyed in a chemical reaction. What are equilibrium reactions? Chemical reactions that stop before all the reactants are used to make the products. What causes equilibrium? 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? 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? 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? Gives the Particles more opportunities to come in contact with each other. What is a catalyst? 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? More chance collisions occur between the reactants, producing more products. What is a solution? A homogeneous mixture of two or more substances. What is a solute? The part of a solution being dissolved. What is a solvent? The part of a solution the solute is being dissolved in. What are compounds? Mixtures of different elements to create a single matter. What are alloys? Solid solutions of metals to make a new one. e.g. bronze ( a mixture between copper and tin) What are Amalgams? A specific type of alloy in which another metal is dissolved in Mercury. What are emulsions? Mixtures of matter that readily separate such as water and oil. What occurs in a synthesis reaction? Two elements combine to form a product. What occurs in a decomposition reaction? Breaks a compound into its component parts. What occurs in a combustion reaction? 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? Carbon dioxide and water. What occurs in a single replacement chemical reaction? An ionic compound reacts with a more active metal to create a new compound. What occurs in a double replacement compound? 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? Two new ionic compounds that have "switched partners" AB + XY --- AY + XB What is chemical bonding? The joining of an atom, element, or chemical to another. What are the two types of chemical bonding? Ionic and covalent What is ionic bonding? 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? When two atoms share electrons. A single covalent bond is the sharing of one pair of electrons. What is the strongest of any bond? The covalent bond. Generally formed by two nonmetals. What is a non-polar bond? When electrons are shared equally What are inter-molecular forces? Weaker forces of attraction between two molecules, such as: hydrogen bonding, dipole-dipole interactions, and dispersion forces. What are hydrogen bonds? The result of the attraction for a hydrogen atom by a highly electronegative element. Which elements are generally involved in hydrogen bonds? Fluorine (F) Oxygen (O2) Nitrogen (N) How strong are hydrogen bonds? Hydrogen bonds are 5-10% as strong as covalent bonds, making them the strongest of the inter-molecular forces. What are dipole-dipole interactions? The attraction of one dipole on one molecule for the dipole of another molecule. How is a dipole created? 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? 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? 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? A momentary dipole, which could be attracted to another momentary dipole of opposite charge in another element or compound. How strong are dispersion forces? Dispersion forces are the weakest of all the inter-molecular forces. What is stoichiometry? The part of chemistry dealing with the quantities and numeric relationships of the participants in a chemical reaction. Rules for balancing chemical equations (stoichiometry) 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? 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. What do oxidation/reduction reactions involve? The transfer of electrons from one element to the next What is oxidation? Loss of electrons What is reduction? Gain of electrons Why is the oxidant reduced? Because it loses an electron How is the element being oxidized and the element being reduced identified? Determining the oxidation states of all elements in the compound. What are the rules to determine oxidation states? Element by itself=0 Group 1A= always +1 Group 2A= always +2 Halogens= +1 positive with Oxygen Monatomic Ion= Ion charge H= +1 with nonmetals -1 with metals O= Usually -2, -1 with peroxide (H2O2) F= Always -1 Sum of ON (oxidation #) for a neutral compound = 0 Sum of ON for a polyatomic ion = ion charge Group 1a of the periodic table includes hydrogen (H), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Highly Nasty Kids Rub Cats Fur Group 2a of periodic table includes beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The halogens include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At) Note-see special rule for Fluorine What are exceptions to the elemental oxidation rule? O2 H2 Br2 N2 I2 F2 What is the effect of acids on metals? Acids are corrosive to metals. What color do acids take when in contact with blue Litmus paper? Red What occurs to acids when mixed with bases? Become less acidic What are bases? Substances that denature proteins, making them feel slick. What color do bases change red Litmus paper to when in contact? Blue What occurs to bases when in contact with acids? They become less basic. What are acids? Compounds that are hydrogen or proton donors What is hydrogen in its ionic state? A proton What is hydronium? A water molecule plus a proton (hydrogen) What group do bases generally have as a makeup of its molecule? Hydroxide (OH) group What is the concentration of acids expressed as? pH What does the pH scale measure? Alkalinity or acidity. Ranges from 0-14 What is the pH of a neutral solution? 7 How are chemical and nuclear reactions different? In chemical reactions, atoms try to achieve stable electron configurations In nuclear reactions, the atom tries to achieve stable nuclear configurations. What is radioactivity? The emission of particles and/or energy from an unstable nucleus. What is radiation? The particles of energy that are transmitted. What are the three types of radiation? Alpha, Beta, Gamma What is alpha radiation? The emission of helium nuclei. The particles emitted contain two protons and two neutrons, causing them to have a charge of plus two (2+). How large are alpha radiation particles? The largest of radioactive emissions. What can stop the penetration of alpha particles? A piece of paper What is beta radiation? The product of decomposition of a neutron or proton. What composes beta radiation? High-energy, high-speed electrons that began as neutrons or protons and "decayed" to electrons. What is the charge of beta radiation particles? Neither positive nor negative How can beta radiation particles be stopped? By a thin sheet of aluminum foil, Lucite, or plastic. These particles have virtually no mass. What is gamma radiation? High-energy electromagnetic radiation, similar to X-rays but with more energy. How penetrating is gamma radiation? Able to go through several feet of concrete or several inches of lead. What is required to protect against gamma radiation? Lead Shielding. How are Isotope symbols written? With a superscript preceding the abbreviation of the element's symbol. What is the nature of isotopes? Some are stable and some unstable. Given enough time, unstable nuclei "decay" into more stable forms. What is the name for the time that it takes for an unstable isotope to decay? Half-life. Some half-lives are very long and some last a few days. The time is different for every radioactive element. What is biochemistry? The study of chemical processes in living organisms What is the function of sugars and starches? To store and provide energy for the body What are the types of sugar? Monosaccharides Dissacharides Oligosaccharides Polysaccharides. What is glycolysis? The process by which glucose is metabolized into 2 molecules of pyruvate to produce 2 molecules of ATP What is another name for the process of oxidative phosphorilation? Kreb's cycle Why is using O2 to oxidize glucose a more effective means of producing energy? Using O2 to oxidize glucose provides more ATP than other O2 deficient systems. What occurs in anaerobic glycolysis? Glucose is converted to lactate instead of pyruvate (as in aerobic glycolysis) When is a situation where the body uses anaerobic glycolysis? Exercise. The burning sensation is caused by lactate production in the muscles. What is gluconeogenesis? The process in which the liver makes glucose from non-carbohydrate sources such as proteins or fats. What composes a molecule of an amino acid? A carbon atom bonded with four groups: Amine (NH2 Carboxyl (COOH) Hydrogen R group What gives each amino acid its own identity? The R group. What is an union of 2 amino acids called? A dipeptide What is an union of a group of less than 30 amino acids called? Peptides or polypeptides What are larger groups of amino acids called? Proteins How many amino acids in humans are necessary to make all proteins for life? 20 What is the makeup of fatty acids? A hydrocarbon chain with an acid group, the carboxy group (COOH), at one end. How does the body use fat? To insulate body organs against shock, maintain body temperature, keep skin and hair healthy, promote healthy hair function, energy storage. What are the classification of lipids? Unsaturated, polyunsaturated, saturated. What composes saturated fats? No double bonds between the carbon atoms of fatty acid chains. What is the composition of unsaturated fats? One or more double bonds between some of the carbon atoms of the fatty acid chains. The more desirable of the fatty acids to consume. What is the function of nucleic acids? Biologic "brain" of life, tells cell what to do and how to do it. Include DNA & RNA Where are nucleic acids found? Most are in the nucleus, some in the cytoplasm, and the mitochondria of cells. What composes the backbone of DNA? Deoxyribose. What is Deoxyribose? A five carbon sugar also called a pentose, and a phosphate "chained" together. How do the sugar-phosphate chain run in the DNA structure? Antiparallel: Opposite directions, one up and one down. How does the structure of DNA differ from that of RNA? RNA is a single strand of ribose, a five carbon carbohydrate, in a sugar-phosphate chain. RNA does not use thymine to form one of its base pairs, instead it uses uracil to bind with adenine.