CHEM 100 exam 2 questions and answers 100% pass.

Which should be larger, the potassium atom, K, or the potassium ion, K+? - correct answers The potassium atom, K, with an additional shell of electrons is larger. How can you tell whether an atom within a compound takes on a positive or negative charge? - correct answers Locate the position of the atom in the periodic table. Why are ores so valuable? - correct answers Metals can be efficiently extracted from them. Atoms of metallic elements can form ionic bonds, but they are not very good at forming covalent bonds. Why? - correct answers They have a great tendency to lose electrons. What holds the positively charged metal ions together within a metallic bond? - correct answers a fluid of negatively charged electrons Why is metal shiny? - correct answers The loose electrons reflect most wavelengths of light. What is an atom with great electronegativity able to do? - correct answers It can pull strongly on bonding electrons Which has a greater electron-pulling power: hydrogen or fluorine? - correct answers Fluorine has a greater electron-pulling power. What is a dipole? - correct answers the separation of a charge Water, H2O, and methane, CH4, have about the same mass and differ by only one type of atom. Why is the boiling point of water so much higher than that of methane? - correct answers -The oxygen of a water molecule has two lone pairs of electrons. -The water molecule is less symmetrical than is the methane molecule. -The electronegativity difference between oxygen and hydrogen is greater than the electronegativity difference between carbon and hydrogen. List the following bonds in order of increasing polarity - correct answers N−N N−O N−F H−F Part complete Would ammonia, NH3, be more or less polar if its shape were triangular planar rather than triangular? - correct answers less polar because of the increased symmetry of the molecule The acronym VSEPR stands for ________. - correct answers Valence Shell Electron Pair Repulsion Which is more polar, a sulfur-bromine (S−Br) bond or a selenium-chlorine (Se−Cl) bond? - correct answers Se−Cl Two molecules, A and B, have very different physical properties. A and B do not mix. Molecule A boils at 80°C and freezes at -30°C. Molecule B boils at 35°C and freezes at -100°C. Which molecule is likely to have the largest dipole? - correct answers molecule A What is the source of an atom's electronegativity? - correct answers positive charge of the nucleus When is the geometry of a molecule not the same as its molecular shape? - correct answers when one or more of the substituents is a lone pair of electrons If an ionic bond is stronger than a dipole-dipole interaction, how can water dissolve an ionic compound? - correct answers The ion-dipole interactions of a bunch of water molecules gang up on the strong ionic bond and pull it into the solution. Why is the surface area of a gecko's foot so extensive? - correct answers The greater the surface area the greater the number of induced dipole-induced dipole forces of attraction that can occur between the gecko's foot and the surface. Consider the boiling points of the following compounds and their solubilities in room-temperature water. Why does the solubilities in water go down as the boiling points of these alcohols go up. - correct answers Larger molecules are more attracted to one another by induced dipole-induced dipole as well as by dipole-dipole and dipole-induced dipole attractions. Which has the strongest dipole? - correct answers sodium chloride, NaCl If you were to increase the pressure of a gas above a liquid (such as by pressing a piston above a liquid) what happens? - correct answers The gas is forced into solution and the solubility increases. Which of the following describes the term concentration? - correct answers It is the amount of solute in a given amount of solution Soaps form micelles when added to water and can be used to remove dirt or grease from surfaces. The dirt or grease molecules get trapped inside the micelle and can be easily washed away using water. Which of the following statements are correct concerning the use of soap to remove dirt or grease from an object? - correct answers -The core of a micelle is formed by hydrocarbon chains. -The polar end of a soap particle interacts with the water molecule. -The dirt particles are generally nonpolar. -Soaps have a polar end and a nonpolar end. When you set a pot of tap water on the stove to boil, you'll often see bubbles start to form well before boiling temperature is ever reached. Explain this observation. - correct answers These initial bubbles are the gases that were dissolved in the water coming out of solution. The solubility of gases in water decreases with increasing temperature. Under which of the following conditions would you expect the highest solubility of oxygen gas in water? - correct answers low temperature and high O2 pressure above the solution What is the difference between the coefficient and the subscript numbers used in a balanced chemical equation? - correct answers Coefficients quantify molecules, whereas subscripts quantify atoms. What does the acronym BAAD stand for? - correct answers Base Accepts and Acid Donates What best describes what happens when an acid such as HCl is mixed with water? - correct answers The proton chemically bonded to the chlorine is transferred to a water molecule and forms a chloride ion and a hydronium ion. When an acid is added to a buffer solution, the pH __________. - correct answers decreases a little What is formed when sodium hydroxide is added to an acetic acid/sodium acetate buffer solution? - correct answers More sodium acetate and water are formed. Which of the following is a trait of an unbuffered solution? - correct answers adding a strong acid lowers the pH significantly Which of the following is a trait of a buffered solution? - correct answers adding a strong acid doesn't significantly change the pH Which of the following items would you use to make a basic buffer solution? - correct answers ammonium hydroxide (a weak base) and ammonium chloride Which of the following items would you use to make an acidic buffer solution? - correct answers acetic acid (a weak acid) and sodium acetate carbonic acid (a weak acid) and sodium bicarbonate A buffer solution works because it _______. - correct answers contains both an acid and a base You encounter a solution that is acidic and you decide to test it by adding a small amount of a strong acid. The pH lowers slightly but is approximately unchanged, and still remains acidic. What can you say about the solution? - correct answers It is a buffer solution. Which of the following acids is the conjugate acid of the bisulfate ion, HSO 4- (acting as a base)? - correct answers H2SO4 In a neutralization reaction ____________________________. - correct answers an acid and a base react to form a salt and water