June 2008 Chemistry Regents #31-40
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|31 The wave-mechanical model of the atom is required to
(1) mass number and atomic number of an atom
(2) organization of atoms in a crystal
(3) radioactive nature of some atoms
(4) spectra of elements with multielectron atoms
|4||wave-mechanical model ==>probable
|32 Magnesium and calcium have similar chemical properties
because an atom of each element has the same total number of
(1) electron shells (3) neutrons
(2) valence electrons (4) protons
|2||same group same valence electrons|
|2||atomic number = # protons
mass number= protons + neutrons
|34 A barium atom attains a stable electron configuration
when it bonds with
(1) one chlorine atom
(2) two chlorine atoms
(3) one sodium atom
(4) two sodium atoms
|2||Ba2+ needs 2 Cl-|
|35 A student measures the mass and volume of a piece of
aluminum. The measurements are 25.6 grams and 9.1 cubic centimeters. The
student calculates the density of the aluminum. What is the percent
error of the student’s calculated density of aluminum?
(1) 1% (3) 3%
(2) 2% (4) 4%
use Table S for actual density 2.698
(2.81*2.698/2.698) * 100%
|36 Given the balanced equation representing a reaction:
2H2 + O2 ==>2H2O
What is the total mass of water formed when 8 grams of hydrogen reacts completely with 64 grams of oxygen?
(1) 18 g (3) 56 g
(2) 36 g (4) 72 g
|4||conservation of mass
if 8g reacts completely with 64g you get 72 grams produced
|37 Which compound contains both ionic and covalent
(3) sodium nitrate
(4) potassium chloride
|3||Write the formula
3 different elements and 1 is a metal
|38 An iron bar at 325 K is placed in a sample of water.
The iron bar gains energy from the water if the temperature of the water
(1) 65 K (3) 65°C
(2) 45 K (4) 45°C
|3||higher than 325K
convert to K by adding 273 to C
|3||they have to be bonded and all are the same structure|
|40 Given the balanced equation representing a reaction:
Cu + S==> CuS + energy
Which statement explains why the energy term is written to the right of the arrow?
(1) The compound CuS is composed of two metals.
(2) The compound CuS is composed of two nonmetals.
(3) Energy is absorbed as the bonds in CuS form.
(4) Energy is released as the bonds in CuS form.
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