1. 1. Pure
substance X is solid at room temperature. If the substance is heated to 230’C
is melted gradually. If cooled to room temperature, the liquid can not be
frozen.
a.
Is it posibble 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 liquid is an element, based
on the information provided?
the answer :
1.
A. X can be considered as an element because it was the one element that can be transformed into solid, liquid or substance at room temperature is at 25 ° C
B. to change the form of the element X physical changes and chemical changes. Indeed, the reaction but the reaction is not a reaction endothermic exothermic reactions but due to the element of the environment to be hot and the system releases heat to the environment. Temperatures and pressures that occur in the element increases.
C. yes, X can be considered as an element that changes the physical and chemical.
1. 2. When
a candle that weight 10gr is burned in oxygen,carbon dioxide and water vapor
formed by combustion the weight more than 10gr.was this case match with the law
of conversation mass. Explain it !
the answer :
2 This happens to wax in accordance with the law of conservation of mass, law of conservation of mass states that the number of substances before the reaction = amount of substance after the reaction. We know that the candles are changed only weighs only while its mass does not change but the same as before and after the reaction. Heavy wax changes from 10gr a> from 10gr.
3. When
carbon burns in oxygen under limited number,it will form two gaseous compounds.
Suggest the way to differentiate the two compounds with one another!
the answer :
how to distinguish the elements that exist in these compounds is to perform testing and to identify physical properties of elements reacted.
4. After
mendeev compiled the periodic table,he concluded that the atomic weights of
certain elements was wrong ruling,and this conclusion was apparently correct.
How mendeev was able to predict that
several atomic weights were wrong? Why his predictions are not always right.
Explain !
the answer :
Two chemist, Lothar Meyer (Germany) and Dmitri Ivanovich Mendeleev (Russia) based on the principle of Newlands, perform classification element. Lothar Meyer prefers the chemical properties of elements while more priority Mendeleev Mendeleev atom.Menurut mass increases: the properties of elements is a periodic function of the relative atomic mass. Meaning: if the elements are arranged according to their relative atomic mass increases, the specific properties will be repeated periodically. The elements that have similar properties are placed in a straight row, called Golongan.Sedangkan horizontal rows, for elements based on the relative atomic mass increases and called Periode.Mendeleev able to predict that there are some elements that wrong by experiment and calculation and the nature of the elements that have similarities. This theory can be refuted if it is found that the new theory can cover the shortage of theories Mendeleev, explaining forecasting and placement of elements on the face of the earth that have not been identified clearly in line with the development of science.
5. When
an aqueous solution of mercury 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 reaction that occurs!
the answer : reaction between mercury chloride and silver nitrate
HgCl2 + AgNO3 →Hg(NO3)2 + 2AgCl
White solid was formed Hg(NO3)2
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