MID TEST
Lecturer : Drs. Syamsurizal, M.Ed
Lecturer : Drs. Syamsurizal, M.Ed
21 November 2011
1. 1 Pure subtance X is solid at room
temperature. If the subtance is heated to 230 c is melted gradually. If then
cooled to room temperature, the liquid can not be frozen
.a I think X is an element, because according to the explanation about
X is a pure substance then I can simpulkn senyawa.karena bhwa X is a single compound is a substance formed from multiple elements through chemical reactions and compounds also can be decomposed again into its constituent elements by chemical reactions. For example, dihydrogen monoxide (water, H2O) is a compound consisting of two hydrogen atoms for every oxygen atom
b. Does it a chemical chage occured? If so can it be said to undergo an endotherm changing, based on the information provided?
Answer
b.yes,Because change is a process or a chemical reaction can not be That Occurs completely happen, obviously re-forms the endothermic reaction,
because there is a decrease in temperature, of the substance with a
temperature of 230 dipnaskan pda temperature and then cooled automatic room temperature turun.pada haracteristics of the reaction is endothermic reaction heat and the temperature Decrease require c. Can it be said that liquid is an element, based on the information provide.
Answer
c. I think not, because the substance X is heated(burned) with a temperature of 230, X reacts with the substance automatic oksiigen to process produced fluidsheted.it so not can be said of an element as it was reacted with compound is the union oksigen.becouse understanding of some elements.
2. When a candle that weight 10g is burned in oxygen, 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!
Answer
. I think not, this includes deviations masa.becouse conservation laws according to the law of conservation of lavosier Antoni is "the substance before and after the reaction is the same". While on a matter that occurred after the addition of the clearreaktion it so this very defiance of the laws of conservation of the .
3. 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. C + O2 CO2 C + 2O2 ⅟ CO
CO, is a colorless gas, odorless, and tasteless. It consists of one carbon atom covalently bonded to one oxygen atom. Carbon monoxide is formed when there is a lack of oxygen in the combustion process.While CO2 or carbonic acid substance is a kind of chemical compound composed of two oxygen atoms covalently bonded to a carbon atom. Carbon dioxide is a gas that is colorless and odorless. When inhaled at concentrations much higher than the concentration of carbon dioxide in the atmosphere,it will taste sour in the mouth and nose and tenggorokan..While CO is harmful when inhaled substance because it is inhaled toxins.
4. 4. After medelev compiled the periodic
table, he concluded that the atomic weight of certain elements wass wrong
ruling, and this conclusion wass apparently correct. How mendeleev was able to
predict that several atomic weights were wrong? Why his predictions are not
always right. Explain
Answer
I think why Mendeleev could know why predictions about the gold atom is wrong ... because he standardized.
repeatedly tried to arrange them so often upside down, plus the atomic determine procedure has not been why prediction not always true .... because according to sya mendelev human also weakness to own, plus the equipment to do research dizaman was not too full
5. When an aqueous solution of merkuri 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.
.
AnswerHgCl2 2AgNO3 2AgCl + + Hg (NO3) 2White precipitate was 2AgCl, because if the anion Ag cations reacted with Cl will produce soluble compounds, which form a white precipitate.
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