1.True or false A. All compounds containing hydrogen are acids. B. None of the p
ID: 920581 • Letter: 1
Question
1.True or false
A. All compounds containing hydrogen are acids.
B. None of the products of nuclear fission are radioactive.
C. A water solution with pH = 4 has a [H+] that is 100 times the [H+] in a solution with pH = 6.
D. Beta rays originate in the nuclei of atoms.
E. A solution of SO3 in water is acidic..
F. The two major components of air are oxygen and argon.
G When an atom emits alpha radiation it becomes a different element..
H. The pH changes when water is added to an acid solution..
I As a radioisotope decays its half life changes.
J. If the pressure on a gas doubles, its volume doubles.
2. A water solution has 2.00x10-5 moles of H+ in 2.00 liters
A. What is the [H+] in the solution?
B. What is the pH ?
C. What is the [OH-] ions?
D. Is the solution acidic or basic ?
E. What is the pH if water is added to make the volume 20.0 liters?
3. Why are nuclear fusion reactions not presently a practical source of energy on earth ?
4. What is the pressure in atmospheres of 12.5 grams of Cl2 gas in A 855mL container at 25.0oC ?
5. Considering the reaction : 2KClO3 2KCl + 3O2 How many liters of O2 gas are produced at 25.0oC and 0.950 atmospheres pressure when 105 grams of KClO3 react?
6. A. An isotope with atomic number 84 and mass number 212 emits an alpha particle. what are the atomic number and mass number of the resultant atom?
B. An atom of atomic number 48 with a mass number of 113 emits A beta particle. What are the new atomic and mass numbers ?
7. Why does the pH change when CO2 dissolves in water ?
8. The 32 isotope of phosphorus has a half life of 14.3 days. How long will It take for a sample of 100g to decay to 12.5g of phosphorus?
9. The maximum legal limit of arsenic in water is 0.0500ppm (parts per million) for drinking water. Is water with 8.00x10-6 moles of As per liter suitable for drinking ? Show how you arrive at your answer.
10. How many grams of NaOH are in 2.00 liters of a 0.255molar solution ?
Explanation / Answer
1)
A) false , NaOH is not an acid , its a base
B) false
c)
we know that
pH = -log [H+]
so
-log [H+] = 4
[H+] = 10-4
in second case
[H+] = 10-6
so
True
D) False
E) True , it forms sulphuric acid
F) False , nitrogen and oxygen
G) True
H) True
I) False , it remains the same
J) False , it depends also on the temperature
2)
we know that
concentration = moles / volume (L)
so
A) [H+] = 2 x 10-5 / 2
[H+] = 1 x 10-5 M
B)
now
pH = -log [H+]
pH = -log 1 x 10-5
pH = 5
C)
now
[H+] [OH-] = 10-14
10-5 x [OH-] = 10-14
[OH-] = 10-9
D)
pOH = 14 - pH
pOH = 14 - 5
pOH = 9
E)
[H+] = 2 x 10-5 / 20
[H+] = 1 x 10-6
pH = -log 1 x 10-6
pH = 6
3) Because it takes more energy to initiate and contain a fusion reaction, than the energy it produces
4) PV = nRT
P x 0.855 = ( 12.5 / 71) x 0.0821 x 298
P = 5
so
the pressure is 5 atm
5)
moles = mass / molar mass
so
moles of KCl03 = 105 / 122.55
moles of KCl03 = 0.857
from the reaction
moles of 02 = 1.5 x moles of KCl03
moles of 02 = 0.857 x 1.5
moles of O2 = 1.2857
now
PV = nRT
0.950 x V = 1.2857 x 0.0821 x 298
V = 33.11
so
the volume is 33.11 L
6)
A)
when alpha particle is emitted
mass number decreases by 4
and
atomic number decreases by 2
so
new atomic number = 84 -2 = 82
new mass number = 212 -4 = 208
B)
when beta particle is emitted
mass number decreases by 0
and
atomic number increases by 1
so
new atomic number = 48 + 1 = 49
new mass number = 113 - 0 = 113
7) it decreases
8) ln C = ln Co - ( 0.693 x t / t1/2 )
ln 12.5 = ln 100 - ( 0.693 x t / 14.3 )
t = 42.91
so
the time taken is 42.91 days
9)
conc = 8 x 10-6 moles / L
1 mole water = 18 x 1000 mg
= 8 x 10-6 x 18 x 1000 mg / L
= 0.144 mg / L
1 mg / L = ppm
conc = 0.144 ppm
it is more than the legal limit
so
not suitable for drinking
10)
moles = conc x volume (L)
moles = 0.255 x 2
moles = 0.51
mass = moles x molar mass
mass = 0.51 x 40
mass = 20.4
so
20.4 grams of NaoH
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