1
1. pure substance x is solid at room temperature.
if the substance is heated to 2300C 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 endoterm changing, based on the information provided?
c.
Can it be said that the liquid is an element,
based on the information provided.
Answer :
a. X is an element of pure a.bahan for chemical elements, or simply called elements, are chemical substances that can not be subdivided into smaller substances, or can not be converted into other chemicals by using ordinary chemical methods. At room temperature (25 C) elements can be either solid, liquid, and gas.
b. In my opinion, no chemical changes in these events because chemistry is the change undergone by an object forming a new substance. While in the event there is no new substance is produced but only changes form or physical yangdisebut with physical changes. physical changes can occur because of changes in the form and any deformities, the X is the material from solid to liquid.
This reaction is not biased to say the reaction is endothermic because the reaction is endothermic reactions require energy or absorb energy from the environment when the reaction occurs, the reaction generally produces dingin.atau temperature endothermic reaction is a chemical reaction that absorbs heat. Heat is taken from the environment so that the enthalpy increases. in the event of such a reaction is not the case because there is no heat transfer from the system and no one called about energy or enthalpy change.
c. Yes, because the fluid including an element or elements at room temperature (25 C) and can be solid, liquid or gas.
2. When a candle that weight 10 gr is burned in
oxygen, carbon dioxide and water vapor formed by combustion the weight more
than 10 gr. Was this case match whit the law of mass. Explain it.
answer :
I think this case is not in accordance with the law of conservation of mass because of the law of conservation of mass, also known as the Lomonosov-Lavoisier law is a law that states the mass of a closed system is constant despite the wide range of processes in the system (in a closed system mass of substances before and after the reaction is the same (fixed / constant)). Statements that are commonly used to express the law of conservation of mass is the mass can change form but can not be created or destroyed. For a chemical process in a closed system, the mass of the reactants must equal the mass of the product.
Lavoiser have observed changes in the nature and substance he argued known as the law of conservation of mass; "In a reaction, the mass of substances before reacting equal to the mass of the substance after reacting". This suggests to us that there is no mass loss during the ongoing reaction.
For example, if we are reacting substance A which has a mass of 10 grams with substance B (mass 10 grams) to produce substances C and D, where mass quantities of substances produced equals the number of reacting mass is 20 grams.
Chemical reactions are written with an arrow, to the left of the arrow are substances which react and to the right of the arrows are substances the reaction.
It is known that the mass after the reaction, is the total mass, which means that the composition of the C and D may be different from the mass of substance A and B are berkomposisi 10 grams and 10 grams. Substance C and D are formed may be 8 grams and 12 grams or 12 grams and vice versa 8 grams. The law of conservation of mass only limits on the amount of the same substance with a substance that occurs before, yet describes compounds formed.
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.
answer :
When carbon burns under a limited amount of oxygen, it forms two gaseous compounds. These compounds are carbon monoxide.
CO (carbon monoxide) gas is highly toxic because it can bind to hemoglobin in the blood thereby blocking the main function of hemoglobin as an oxygen carrier, formed in incomplete combustion of carbon-containing fuels such as wood and gasoline, because it can burn and produce heat, then gas is used as fuel gas as the reductant in metal processing, making methanol.
carbon monoxide with H2O that forms the central atom lone pair to form a dipole moment so it is polar. based on the nature of the polarity of the molecules makes it possible to separate the pollutant gas molecules using molecular screening in accordance with the properties of impurity gas polarity.
4. After mendeev compiled theperiodic table, he
conclude that the atomic weight of certain elements was wrong ruling, and this
conclusion was apparently correct. How Mendeleev was able to predict that
several atomic weight were wrong? Why his predictions are not always right.
Explain!
answer :
Dmitri Ivanovich Mendeleev in 1869 observations of 63 known elements and get the result that properties of elements are a periodic function of the relative atomic mass. Certain properties will be repeated periodically if unsurunsur ordered by relative atomic mass increases. The next Mendeleev placed elements with similar properties in the vertical column called class. These elements have also been prepared by the increase relative atomic mass and placed in a column called period.
Mendeleev deliberately emptied a few places to establish similar properties in the group. Some boxes also intentionally left blank because Mendeleev sure there's an element of the unknown because it has not been found. One element that is in line with the forecast germanium Mendeleev was previously named ekasilikon by Mendeleev.
The weakness of this theory is still contained elements of a larger mass that lies in front of a smaller mass elements. Co: Tellurium (te) = 128 in kiriIodin (I) = 127. this is because the elements have properties kemirpan placed in one class. The weakness of this theory is the atomic mass correction. Previous atomic mass. In previous atomic mass = 76-113. besides Be, 13.5 to 9. N 120-240.
However, the law considers Mendeleev periodic can not tolerate any exceptions as any deviation from the order of elements by atomic weight. For example, in the case of the elements tellurium and iodine, he predicted that the atomic weights of the two elements is not appropriate because the value provided suggest the opposite order to what is determined by the chemical nature. More specifically, tellurium showed a higher atomic weight in accordance with the values and subsequently measured based sequence element tellurium features will be put in the same chemical group as fluorium, klorium, and bromium, where it is not included in the periodicity of the used chemistry. Apparently, according to Mendeleev reversal sequence that is true but the reason is used inappropriately. The atomic weight is actually approaching accuracy, but the order of elements is better placed by the number of atoms of each element. Schematic sequence elements enhanced by the work of Moseley in 1912, and on the main complication lies in the mixture of isotopes occurring chemical elements are most important.
Mendeleev periodic believes that the law can be used to predict the existence and properties of some new element compounds, as well as to correct the atomic weights of some elements are already known. However, historian and author of chemistry are emphasized in the legal aspects of prediction. Mendeleev ability to accommodate elements that are known to have contributed positively in the periodic system. For example, the quote that accompanies her awarded the Davy Medal by the Royal Society of London does not mention any of his predictions.
1 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 reaction that occurs.
answer :
HgCl2 +2 AgNO3 ---> Hg (NO3) 2 +2 AgCl
the resulting white powder is silver nitrate (AgCl)
