General Chemistry Chapters 19, 21, 22 Essay

1175 Words Oct 26th, 2013 5 Pages
HOMEWORK EXAM 3:

Chapter 19:

The half life of 90Sr is 29 years. What fraction of the atoms in a sample of 90Sr would remain 175 years later?
Answer

0.166

0.125

0.062

here
0.015

Which relation is not correct?
Answer

11p = 11H = proton

0-1e = 0-1β = electron

here
+10e = +10β= positron

10n = neutron

As a result of beta decay, the product nucleus is
Answer

one atomic number lower than the original element.

two atomic number higher than the original element.

here one atomic number higher than the original element.

two atomic number lower than the original element.
What is X for the nuclear reaction: 21284Po à 20882Pb + X
Answer

42p

1-1β
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T

Enhancing the ability of a semiconductor to conduct electricity by adding small amount of certain impurities to the element.

Enhancing the ability of a semiconductor to conduct electricity by adding significant amount of certain impurities to the element.

What is the correct sequence of the recovery ofa metal from its ore?
Answer
T

preparation of the ore --> production of the metal --> purification of the metal

preparation of the ore --> purificaiton of the metal --> production of the metal

purification of the metal --> preparation of the ore --> production of the metal

production of the metal --> purification of the metal --> preparaiton of the ore

Which one of the following is the best electric conductor?
Answer
T

Mg

C

Si

P

CHAPTER 22
Which aqueous solution of oxoacids of the halogens is the strongest acid?
Answer

HClO

HClO2

HClO3

Here check
HClO4

Which one is not metal?
Answer

Li

Be

Here (mettaloid) check
B

Sn

Which oxide is basic?
Answer

SiO2

SO3

Here (alkaline earth met)?
MgO

Cl2O7

Which is not an isotope of hydrogen?
Answer

hydrogen

tritium

deuterium

Here check dextrium Which one is in mismatch?
Answer

Ammonia - NH3

Nitrous oxide - N2O

Nitric oxide - NO

Nitrous acid check
HNO2 - nitiric acid

Which aqueous solution of hydrogen halide is the weakest acid?
Answer

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