Mid
Semester Test
Course : Basic Chemistry
Credit : 3 SKS
Lecturer : Dr. Syamsurizal
Credit : 3 SKS
Lecturer : Dr. Syamsurizal
(
Chairani Adelia – RSA1C112016 )
Attention : Blog
Version.
You are permitted to accsess the internet and open books but not allowed to
cooperate or cheat, when find out, it bring about fail. You answere could be
upload at your blog. Time: 08.00 – 17.00 WIB.
1.
Pure subtance X is
solid at room temperature. If the subtance is heated to 230o C is
melted gradually. If then cooled to room temperature, the liquid can not be
frozen.
a. Is
it Possible X of an element or a compound. Explain it!
b. Does
it a chemical change occured ? If so can it be said to undergo an endotherm changing,
based on the information provided?
c. Can
it be said that the liquid is an element, based on the information provided.
2.
When a candle that
weight 10 g is burned in oxigen, carbon dioxide and water vapor formed by
combustion the weight more than 10 g. Was this case match with the law of
conservation of mass. Explain it!
3.
When carbon burns in
oxigen under limited number, it will form two gaseous compounds. Suggest the
way to differentiate the two compounds with one another.
4. After
Mendeleev compiled the periodic table, he concluded that the atomic weight of
certain element was wrong ruling, and this conclusion was apparently correct.
How Mendeleev was able to predist that several atomic weights were wrong? Why
his predictions are not always right. Explain
5. When
an aqueous solution of mekuri chloride is added to an aqueous solution of
silver nitrate, a white solid forms. Identify the white solid and write the
balanced equation for the reactions that occurs.
Answer :
1.
A. X is a compound. The compound is a combination of two elements or more
are joined chemically by a certain ratio in each of the molecule. If the
compounds in the melt with the heat will melt more mudah.Tapi it would cai,
liquid hard freezes at the same temperature setting before him melt. If you
want to make it freeze the requirement is much lower temperatures. Maybe the
temperature below 0 ℃.
B. chemical changes that occur can be called
endothermic reactions. Endothermic reaction is a reaction that is accompanied
by heat transfer from the environment to the system (heat absorbed by the
system from its environment), characterized by a decrease in the ambient
temperature around the system. Substance X are initially solid when heated at a
temperature of 230 ℃ melting in the heat in the environment caused by the move to the substance, that
substance will melt and the temperature of the substance to be higher than
the ambient temperature.
the ambient temperature.
C. I
think it can be said fluid element, because
the element is a constituent or the
bottom of an element. Where the
liquid element is the element that
is composed of elements, such as when liquid is added hydrochloric acid with
sodium hydroxide to form sodium chloride. ((HCl + NaOH à
NaCl ). for instance soy liquid
while.
2.
The law of
conservation of mass is' In a reaction, the mass of substances before
reacting equal to the mass of the
substance after reacting ". in
this case the mass of wax in
the fuel would be equal to the mass of wax before
the fire. While the wax melts, it remains still wax, which changes only the shape alone. Candles will burn
the gas and the amount of energy (heat and
light). If the
combustion products collected
and weighed, certainly mass equal
to the mass plus the mass of oxygen candles that
are used in the arson. Thus, this case can be said to be in accordance with
the law of conservation of mass.
3.
How to
distinguish between the two compounds to
each other by doing an experiment to see his or
elements making up the difference. As
such, research that generates data
analysis that can be seen is a striking difference between
the two compounds is gas so we
can see the difference that occurs between the
two. Perhaps as a
qualitative experiment.
4.
Predictions are
not always
correct because, in
the Mendeleev periodic system
of elements such as hydrogen are deviations from the
other elements are not described. In
1869, Dmitri
Ivanovich Mendeleev Russian
chemist nationality arrange 65 elements
known at that time. Sort of increasing atomic mass
of the element Mendeleev and chemical
properties
At the same time, Julius Lothar Meyer made the arrangement of elements such as dikernukakan by Mendeleyev. Just, Lothar Meyer arrange elements based on their physical properties. Although there are differences, but both result in the same grouping elements.
Mendeleev provide empty boxes to place elements of the time it has not been found, such as the element with mass number 44,, 68 72, and 100. Mendeleyev had predicted the properties of elements and it is a prophecy after the elements were discovered. The composition of elements Mendeleev perfected under the law and called the Mendeleev periodic system.
Mendeleev periodic system consists of a group (the element that is located in one column) and period (elements located in one line)
At the same time, Julius Lothar Meyer made the arrangement of elements such as dikernukakan by Mendeleyev. Just, Lothar Meyer arrange elements based on their physical properties. Although there are differences, but both result in the same grouping elements.
Mendeleev provide empty boxes to place elements of the time it has not been found, such as the element with mass number 44,, 68 72, and 100. Mendeleyev had predicted the properties of elements and it is a prophecy after the elements were discovered. The composition of elements Mendeleev perfected under the law and called the Mendeleev periodic system.
Mendeleev periodic system consists of a group (the element that is located in one column) and period (elements located in one line)
5.
HgCl2 + 2AgNO3 à Hg(NO3)2
+ 2AgCl
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