Chemistry Unit 2 Practice Problems

Cu atoms are smaller than Ag atoms, thus they interfere more with the displacement of atoms in the alloy

A Cu has two common oxidation states, but Ag has only one B Cu has a higher mp than Au has, but Ag has a lower mp than Au has C Cu atoms are smaller than Ag atoms, thus they interfere more with the displacement of atoms in the alloy D Cu atoms are less polarizable than are Au or Ag atoms, thus Cu has weaker interparticle forces

equally shared and form nondirectional bonds

a particle-level diagram of a metallic element is shown above. typically, metals are both malleable and ductile. the best explanation for these properties is that the electrons involved in bonding among metal atoms are

ionic solids do not have free movement of ions. when dissolved, the ions are free moving. this allows electricity to flow

an ionic solid does not conduct electricity, but does conduct electricity when dissolved in water. which of the following explains why? a. water is polar so it readily conducts electricity. the ionic solid does not play a role. b. the ionic solid has too small of spaces between particles for electricity to flow. water moves the particles apart enough to conduct electricity. c. ionic solids do not have free movement of ions. when dissolved the ions are free moving. this allows electricity to flow. d. ionic solids are too big to conduct electricity. when dissolved, the solid gets smaller and then can conduct electricity

b

copper atoms and zinc atoms have the same atomic radius, 135 picometers. based on this information, which of the following diagrams best represents an alloy containing only copper and zinc atoms?

C--F, C--Cl, C--Br

place the following in order from strongest bond energy to weakest. C-Cl, C-Br, C-F

b

steel is an alloy containing Fe atoms and C atoms. which of the following diagrams best represents the particle-level structure of steel?

the carbon-to-selenium bond is nonpolar covalent

the elements C and Se have the same electronegativity value, 2.55. which of the following claims about the compound that forms from C and Se is most likely to be true?

the charge of the Mg cation is larger than that of the Na cation

the energy required to dissociate an ionic solid into gaseous ions (lattice energy) for the compounds NaF and MgF2 is shown in the table above. on the basis of Coulomb's law, which of the following best helps to explain the large difference between the lattice energies of NaF and MgF2? NaF lattice energy: 930 kJ/mol MgF2 lattice energy: 2978

oxygen has a -2 charge, whereas Cl has a -1 charge. this results in a stronger attraction for Na2O

the energy required to dissociate an ionic solid into gaseous ions is known as the lattice energy. sodium chloride, NaCl, has a lattice energy of 787.3 kJ/mol. sodium oxide, Na2O has a lattice energy of 2564 kJ/mol. which explanation best accounts for this difference?

Sr2+ ion is larger than the Mg2+ ion because it has more occupied energy shells. coulomb's law state that the force of attraction between cation and anions is inversely proportional to the square of the distance between them. since the distance between Sr2+ and OH- is longer than the distance between Mg2+ and OH-, the attractive forces in Sr(OH)2 are weaker and its lattice energy is smaller

the energy required to separate the ions in the Mg(OH)2 crystal lattice into individual Mg2+(g) and OH-(g) ions is known as the lattice energy of Mg(OH)2(s). the lattice energy of Sr(OH)2(s) is less than the lattice energy of Mg(OH)2(s). explain why in terms of periodic properties and coulomb's law. Mg(OH)2(s)-->Mg2+(g) + 2OH-(g) lattice energy: 2900 kJ/mol Sr(OH)2(s)-->Sr2+(g) + 2OH-(g) lattice energy: 2300 kJ/mol

a

the particle level diagram above represents the structure of solid KF. although the mass of KCl is greater than that of KF, the density of KCl is actually LESS than that of KF. which of the following representations of the structure of KCl best helps to explain this phenomenon?

yes. in the C--O bond, there are less electrons being shared (2 vs. 6) so the nucleus of carbon (or oxygen) will be less attracted to the bonding electrons. as a result, the bond length will be longer, and the bond energy will be less than the C--O triple bond

the potential energy diagram is given for C-O double bond. a student claims that the curve for a C-O would be less deep and would be shifted to the right of the curve for C-O triple bond. do you agree with this claim? explain why or why not.

it contains ionic bonds

two pure elements react to form a compound. one element is an alkali metal, X, and the other element is a halogen, Z. which of the following is the most valid scientific claim that can be made about the compound?

B--Cl, P--F (greater diff in eneg). Cl and F

which bond is more polar: B--Cl or C--Cl P--F or P--Cl. indicate in each case which atom has the partial negative charge

Se--Cl

which of the following bonds is most polar: S--Cl, S--Br, Se--Cl, or Se--Br?

it does not conduct electricity because its ions cannot move freely within the solid

which of the following correctly indicates whether the solid represented by the particulate model shown above conducts electricity and explains why or why not?

a (interstitial alloy)

which of the following diagrams best depicts an alloy of Ni and B?

the bond is highly polar

which of the following scientific claims about the bond in the molecular compound HF is most likely to be true?

a

white gold is a common alloy of gold and palladium that is often used in jewelry. the atomic radii of the metals are given in the table above. Au: 135 atomic radius pm Pd 140 atomic radius pm a. a particular ring is made from an alloy that is 75 mole percent gold and 25 mole percent palladium. using the box below, draw a particle level diagram of the solid alloy consisting of 12 atoms with a representative proportion of atom types. your diagram should clearly indicate whether the alloy is interstitial or substitutional. use empty circles for gold and shaded circles for palladium

iodine has a larger radius than bromine so attractions will be weaker

why does KBr(672 kJ/mol) have a higher lattice energy than KI (632 kJ/mol)?