Regents Chemistry Exam Explanations January 2003

Questions

Answer

Explanations

11 Which type or types of change, if any, can reach equilibrium?

(1) a chemical change, only
(2) a physical change, only
(3) both a chemical and a physical change
(4) neither a chemical nor a physical change

both

12 An increase in the average kinetic energy of a sample of copper atoms
occurs with an increase in

(1) concentration (3) pressure
(2) temperature (4) volume

definition temperature- average kinetic energy

13 The empirical formula of a compound is CH₂ . Which molecular formula
is correctly paired with a structural formula for this compound?

carbon must have 4 bonds

formula is a multiple of CH₂

This equation represents the formation of a

(1) fluoride ion, which is smaller in radius than a fluorine atom
(2) fluoride ion, which is larger in radius than a fluorine atom
(3) fluorine atom, which is smaller in radius than a fluoride ion
(4) fluorine atom, which is larger is radius than a fluoride ion

gaining an electron will make the new ion bigger than that of the original atom

15 The high electrical conductivity of metals is primarily due to

(1) high ionization energies
(2) filled energy levels
(3) mobile electrons
(4) high electronegativities

metal- a lattice of positive nuclei immersed in a sea of mobile electrons

16 One similarity between all mixtures and compounds is that both

(1) are heterogeneous
(2) are homogeneous
(3) combine in a definite ratio
(4) consist of two or more substances

mixtures- homo or heterogeneous

compounds-homogenous only (pure)

17 Which phase change results in the release of energy?

S	L	G
1------------->
2----------------------->
3 ------------->
4<-----------------------

there must be 4 carbons to have isomers (butane)

19 What occurs when NaCl(s) is added to water?

(1) The boiling point of the solution increases, and the freezing point
of the solution decreases.
(2) The boiling point of the solution increases, and the freezing point
of the solution increases.
(3) The boiling point of the solution decreases, and the freezing point
of the solution decreases.
(4) The boiling point of the solution decreases, and the freezing point
of the solution increases.

When a solute is added to water the boiling point increases and the freexing point decreases. This is proportional to the amount of particles in the solution (remember ionic subs. break up)

20 Which radioisotope is a beta emitter?

(1) ⁹⁰Sr (3) ³⁷K
(2) ²²⁰Fr (4) ²³⁸U

Use Table N- Decay Mode