CH 205 Final Test

1. What is the kinetic energy in Joules of a 2100-lb car traveling at 48 miles per hour? (1 lb = 0.4536 kg, 1 mi = 1.609 km)

mass $m = 2100*0.4536 =952.56 kg$

speed $v = 48*1.609 =77.232 km/h = 77232/3600 =21.45 m/s$

$Ec = m*v^2/2 =952.56*21.45^2/2 =219205.7 J$

2.  Given a $4AlCl3(s) + 302(g) → 2Al2O3(s) + 6Cl2(g)$; ∆H = ─529.0 kJ Determine ∆H for the following thermochemical equation: $Cl2(g) + ⅓Al2O3(s) → ⅔AlCl3(s) +  ½ O2(g)$

$\Delta1(H) = -\Delta(H)/6 =-(-529)/6 =88.167 kJ$

3.  A section of the periodic table with all identification features removed is shown below: VWXYZ  Which element is the smallest atomic radius? _____ V 

The atomic radius is proportional to the number of electrons the element has. V has the fewest electrons.

4.  Below is data on the first four (4) ionization energies for a fictitious element X

    First ionization energy = 2000 kJ/mol
    Third ionization energy = 2500 kJ/mol
    Fourth ionization energy = 25000 kJ/mol
 From the data, which of the following statement is incorrect?

   X could belong to Group IIIA.
    The fourth ionization energy = is much greater than the third ionization energy = because X3- consists of a noble-gas core or a pseudo-noble-gas core.
    The third ionization energy = is greater than the second ionization energy because X3- has a bigger charge than X+.
    X could belong to Group IIIB
    X could belong to Group VA.
    is incorrect. X(3-) has a lower charge than X(+)
also a), d) and e) are incorrect. The element in cause is Ne and it belongs to group VIII.

In Bohr’s atomic theory, what happens (in terms of energy and/or light) when an electron moves from one energy level to another energy level more distant from the nucleus?

The electron needs to absorb energy (a light quanta) from outside the atom in order to be able to move to an energy level more distant from the nucleus.

Write the chemical equation that shows the first ionization for strontium. All indices () must be superscript.

(38)Sr -1e(-) = (38)Sr(-)

The ground state valence-shell configuration of a particular atom is 4d10 5s25p1 . The element to which this atom belongs to what block-type (s, p, noble-gas, etc.) on the periodic table? ______

It belongs to the block type p. The element is In (Indium) and is located in the group III, period 5, has Z = 49 and A =115.

Write the chemical equation that shows the second ionization for calcium. All indices must be superscript

(20)Ca(-) -1e(-) =(20)Ca(2-)

Rank the following ions in order of increasing first ionization energy: O2– , Mg2+, F– , Na+

O(2-), F(-), Na(+), Mg(2+) if the question is about ion ionization energy

Na, Mg, O, F if the question is about atom ionization energy.

10. What is the wavelength of a photon having a frequency of 3.00 x 1015 Hz?

    (c = 3.00 x 108 m/s, h = 6.63 x 10—34 J s)
$wavelength = c/frequency  =3*10^8/3*10^{15} =10^{-7} meter =100 nanometer$

11.  The electron affinity value expected for the process Cl(g) +e—  Cl– ,(g) would be

    a) a large negative number
    b) a small negative number
    c) zero
    d) a small positive number
    e) a large positive number
The correct answer is e) a large positive number. Cl ionizes very easy. For Cl it is 349 kJ/mol which is big.

12.  What is the quantity of heat evolved at constant pressure when 60.9 g H2 O(l) is formed from the combustion of H2 (g) and O 2(g)?

    H2 (g) + ½O2(g) → H2O(l); ∆H0 = ─285 kJ

1 mol $H_2O$ ………2+16=18 grams
x mol $H_2O$ ……….60.9 grams

x =60.9/18 =3.38 mol

Total heat $Q =x*\delta(H) =285*3.38 =964.25 kJ$

13. Consider the following metals

        Metal            Specific Heat
Copper            0.385 J(g 0C)
magnesium        01.02 J(g 0C)
mercury        0.138 J(g 0C)
silver            0.237 J(g 0C)
lead            0.129 J(g 0C)
 If the same amount of heat is added to 25.0 of each of the metals, which are all at the same initial temperature, which metal will have the highest final temperature? (Show all your work)

The answer is lead will have the highest final temperature because it has the smallest specific heat.

14.  Given  that

    O(g) + e–  → O(g); ∆H = ─142 kJ
    O(g) + 2e–  → O2–  (g); ∆H = ─702 kJ
 Which is the enthalpy change for the reaction represented by the following equation?

    O– (g) + e–  → O2–  (g)

$\Delta(H) =-702-(-142)= 560 kJ$

15. Fe has __________ (provide a number) electrons that is (are) unpaired in its 3d orbital’s.
Fe has 6 electrons on to the 3d orbital. From these 4 are unpaired (the 3d orbital has 5 sub orbitals, one suborbital has 2 paired electrons on it and the other 4 have only one unpaired electron on them)

16.  see attached Word document

None of the above orbital violates the Pauli exclusion principle ( which says that there are allowed only 2 electrons of different spin into an orbital or suborbital)

17. What is ∆H0 for the following phase change? NI(s) → NaI(l)

Substance     ∆H0 f (kJ/mol)
NaI(s)             ─287.86
NaI(l)             ─266.51

$\Delta(H) =-266.51-(-287.86) =+21.35 kJ/mol$

Write a set of quantum numbers (n, l, m1, ms) that refers to a 3d orbital?
(3, 2, m(l), m(s)), where m(l) =-2,-1,0,+1,+2 and ms=-1/2, +1/2

            hence a possible set is (3, 2, 2, 1/2)
 The maximum number of electrons that can be accommodated in an f sub shell is 14 electrons. Orbital f has the quantum number l =3 and there are 2*(3*2+1) possible electrons on it.

How many valence electrons does an arsenic atom have?

As is in group V, hence it has 5 valence electrons.

Write the set of four quantum numbers (n, l, m1, ms) that correctly describes one of the valence electrons in a ground state radium atom?

(7, 0, 0, +1/2)

The elements that are filling the 5f sub shell are called Lantanides and Actinides.

23.  The angular momentum quantum number of the two highest-energy valence electrons in an atom of lead is l = 1

The phosphorus atom would be expected to have 3 (provide a number) unpaired electrons in its ground state. It has 5 valence electrons. Of these only 3 are unpaired.

25. An atom of which of following elements is not diamagnetic in the ground state?

    Ba, Kr, Hg, Pt
Pt and Ba are not diamagnetic in their ground state.They are paramagnetic.