BASIC CHEMISTRY 1 MID TEST

BASIC CHEMISTRY 1 MID TEST
NAMA : FITRIANI
NIM      : RSA1C112013

1. X pure material is solid at room temperature. if the substance is heated to 230 C melted gradually. if it is   

     then cooled to room temperature, the liquid can not be frozen.
   a. that x may be from an element or compound. explain it!
   b. Is it a chemical change occurs? if so could be said to undergo change endotherm, based on the   

        information provided?
  c.can said that the liquid is an element, based on the information provided

         Answer:

a. X is included compounds. Because the compound is a single substance that is chemically still be broken down into other substances much simpler where nature is different from the original substance. The smallest part of a compound is a molecule (a combination of two atoms of the element / more better kind or different kinds. Example, white sugar, solid, and sweet taste when heated to burn will have a reaction. Water also belong to the compound. Air can be decomposed into two other substances, namely hydrogen and oxygen gas. decomposition of water can occur when water vapor is heated at high temperatures or if the water is electrified. properties of hydrogen and oxygen gases vary with the nature of water. flammable hydrogen gas, while oxygen is a gas required in the combustion process. while water can not burn and can not hold burning. Thus, water can not be frozen at room temperature, but can be frozen at a temperature of O ° C.b. occur. Since X can fuse although gradually. The reaction is endothermic reaction the heat transfer from the environment to the system. marked drop in the ambient temperature around the system.c. yes, because it is the basic constituent element of the element. Air includes an element because it is composed of hydrogen and oxygen.

2. When the candle that weighs 10 g burned in oxygen, carbon dioxide and water vapor formed by the combustion of more than 10 g weight. This was the case in accordance with the law of conservation of mass. Explain!

Answer:
  Law of Conservation of Mass presented by Antoine Laurent Lavoisier (1743-1794), which reads: "In a reaction, the mass of substances before and after the reaction is the same", in other words, the mass can not be created and can not be destroyed. This means that as long as there is no reaction occurs atoms reactants and reaction products were missing. So candles are lighting source which consists of axis covered by solid fuel. materials made from paraffin wax, which is a mixture of hydrocarbons of Alkane (molecular chains of carbon atoms and hydrogen atoms long), the material we have encountered in petroleum. As implied in its name, only the hydrocarbon molecules consist of atoms of hydrogen and carbon atoms.
   Results of the observation:a. Observation Results Candle Burned BeforeQualitative Sense• Color white candles• Color white wick• Candles odorless• smooth wax surface• Establish regular wax cylinder to the top of the cone'sEyeNoseSkinEyeQuantitative gauge• High candle 16 cm• High-wick candle 17 cm• 1.8 cm diameter candle• Weight 40.19 grams wax before the fire RulerRulerRulerBalanceb. Observation Results Candle Burned AtQualitative Sense• The color remains white candles• a burning fuse color black• The end of the fuse is lit like burning embers• Burning candles produce light• Fire the top of the yellow and blue flames bottom• Some time after the initiation of burnt wax melting• molten hot wax• The molten wax is still hot nodes• The air around the hot fire EyeEyeEyeEyeEyeEyeSkinEyeSkinQuantitative gauge• The length of fire 3 cm• The cone candle began to disappear during combustion at minute - 6• In minute - 10 14.2 cm height candles• In minute - 20 13 cm height candles• In minute - 60 5 cm height candles RulerStopwatchRulerRulerRulerc. After the results of observations Candle BurnedQualitative Sense• Shortly after the fire burned off a pungent smell• Shortly after the fire off of the wick candles emit black smoke• The color remains white candles• Color wick burnt black• The wax becomes irregular• Nose rough surface waxEyeEyeEyeSkinQuantitative gauge• The length of 5 cm wax• The length of the wick, 6 cm• Weight 19.71 grams burned candles after RulerRulerBalanceSo candles are included in the law of conservation of mass.

3. When carbon burns under a limited amount of oxygen, it forms two gaseous compounds. Suggest a way to differentiate the two compounds with one another.

Answer:
he difference in one compound with another compound when seen from the structure is obviously different for different compounds. When viewed from its differences are at the boiling point and freezing point. If the reagent is reacted with the same result in different products. Example:
               C + O2 ==> CO2Carbon Dioxide

              2C + O2 ==> COCarbon monoxide

4. After mendeev preparing the periodic table, he concluded that the atomic weights of some elements was the wrong decision, and this conclusion appears to be true. How mendeelev able to predict some of the atomic weights is wrong? why his predictions are not always right. Explain!

Answer:
According to Mendeleev: the properties of elements are 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 the Group. While the horizontal rows, for elements based on the relative atomic mass increases and called Period.Mendeleev SYSTEM FLAWS1. The length of the period is not the same and why not described.2. Some elements are not ordered by their atomic mass increases, for example: Te (128)
     before I (127).3. Mass difference of successive elements are not always 2, but the range between 1 and 4
     so it is difficult to predict the mass of an element that has not been known.4. Valence more than one element of the unpredictable group.5. Anomaly (deviation) of the elements hydrogen to another element not explained.6. There are still elements of the larger mass located at the front element
     smaller mass. Co: Tellurium (te) = 128 in kiriIodin (I) = 127. this is because
      element that has properties kemirpan placed in one group.7. Pemebetulan atomic mass. In previous atomic mass = 76 to 113. besides it Be,
      from 13.5 to 9. U from 120 to 240.

5. When the mercury chloride solution is added a solution of silver nitrate, a white solid forms. Identification of a white solid and write a balanced equation for the reaction that occurs

Answer:

HgCl2 + 2AgNO3 ---> Hg (NO3) 2 + 2AgClThe resulting white powder is silver nitrate (AgNO3)