mid semester test

Question1. X of pure solid substance at room temperature, if the substance is heated to230meleleh gradually. if it is then cooled to room temperature, the liquid can not be frozen
a. is it possible x element or compound. explain
b. whether the chemical changes that occur? if so it can be said menjalaniperubahanendotherm, based on the information provided?
c. can be said that the fluid elemet, based on information supplied
2. when a weight of 10 g of wax that can be burned in oxygen, carbon dioxide and water vapor formed by combustion weigh more than 10 g. This is the case in accordance with law conservation of mass, explain
3. when carbon burns in oxygen under a limited number, it will terbentuksenyawa gas.suggest ways to differentiate the two compounds with one another
4. after Mendel arrange the periodic table, he concluded that the atomic weights of certain elements govern wrong, and this conclusion seems correct. how Mendelmampu pedictthat some of the atomic weights? why the predictions are not always right, explain
5. when a dilute solution of mercury chloride was added to a solution of silver nitrate, awhite solid form. identify white solid writing equations seimbanguntuk reactionAnswer !1. A. Compounds because like the above that the substance melts, and compounds thatcan be either solid, liquid and gas, and the statement according to the characteristics ofcompounds
B. because the state tersebutsubtansi mengabil heat from the outside and the statement in accordance with the description of the reaction endotrem
C. because the problem is in saying that in the melt and surely he is solid and in accordance with the characteristics of compounds

2. In my opinion not appropriate because in a matter of explanation and not in accordancewith the law of conservation of mass of a substance before and after the reaction is constant or the same, which in penjelasanya sedangankan antra different before and afterthe reaction because of its mass is not the same between before and after

3. the combustion reaction

4. I think mendelev correct predictions because it is capable of predicting the elements that have not in the know and predict a definite future in ketemukan new element and it wasproven, because mendelev compile atom - atom is based on the increase in mass, andprediks imendelev it right not wrong

5.HgCl2 + AlN4  = 2HgCl + 2AlN2

STOICHIOMETRY

In chemistry, stoichiometry (sometimes called reaction stoichiometry to distinguish it from composition stoichiometry) is the study and calculate the quantitative relationships of the reactants and products in chemical reactions (chemical equations). This word comes from the Greek stoikheion (elements) and metriā (size).

Stoichiometry based on fundamental laws of chemistry, namely the law of conservation of mass, comparative law remains, and the law of multiple comparisons.


Stoichiometric gas is a special form, where all the reactants and gaseous products. In this case, the coefficient of substance (mole ratio is expressed in reaction stoichiometry) also once stated volume ratio between the substances involved.

LAW OF CHEMICALBasic Chemical  s laws
 1.Law of Conservation of Mass
 1. The Law Of Conservation of massHukum ilmuwankimia conservation of mass was introduced by France, Antoine Lavoisier in 1787. It was believed that the combustion reaction parailmuwan menghasilkangas
 phlogistonso that the mass of substance after combustion lebihsedikit than before. It is based padapercobaan conducted Pristley. Pristley oksidaraksa heating (red calx of mercury). Heating the reaction solids oksidaraksa mercury and gas producing colored diatasnya.Setelah not weighed, the mass of mercury less than massaoksida mercury.The law of conservation of mass was found by French chemist, Antoine Lavoisier in 1787. At the time, scientist believed phlogiston That resulted combustion gases, so That the mass of matter after combustion was less than before. It was based on  Priestley's experiments. Priestley heated red calx of mercury and it produced mercury in aqueous and colorless gas above. After it was Measured, the mercury mass was less than the mass of mercury oxide.Pristley colored gas does not mention it in terms of phlogiston. However, not demikiandengan Lavoisier, he doubted the existence of phlogiston gas. Presumably, the dimaksudflogiston is oxygen gas. Later, Lavoisier repeated the experiment pristley untukmembuktikan expected. He weighed mass of the substance before and after the reaction of mercury pemanasanoksida carefully on a balance sensitive. Apparently, there penguranganmassa mercury oxide.Called That Pristley colorless gas as phlogiston. However, doubted the existenceof Lavoisier phlogiston gas. He proposed the phlogiston That was Actually oxygen gas. Then, Lavoisier repeated pristeley  s experiments to approve his opinion. He Measured the mass of mercury oxidebefore and after the combustion using a very sensitive measure. That he found there was adecrease in mercury oxide mass.Lavoisier explains the reason for the reduced mass after pemanasan.Ketika heated mercury oxide, mercury oxide produces oxygen gas so that its mass will berkurang.Lavoisier also proves the opposite. If a metal is heated in air, its mass will increase with the amount of oxygen taken from the air. Conclusion Lavoisiertersebut known as the law of conservation of mass (amount of substance before  and  sesudahreaksi unchanged).
Lavoisier explained the reason why mercury oxide Decreased mass. When it was heated, mercury oxide produced oxygen gas, so its mass was Decreased. Lavoisier also proved theopposite reaction. If a metal was heated in water, along with its mass Increased the number of oxygen taken from the water, Lavoisier conclusion is Called the law of conservation of mass (amount of matter Thetotal  of the reaction compounds  Remains constant).

  Comparison of mass elements of Cu and O in the CuO compounds according to the results percobaanPercobaanKe-Before Heating (g copper) After the Warming (g copper oxide) Comparison of the mass of oxygen in copper oksida1 tembagadan 6.4
2
8.04
  
 
      

=
  
 
 

=

  


2
9,48 11,88
  
  

 
   

=
  
 
  
=

  

  The mass of copper in copper oxide with copper mass sebelumpemanasan assuming all copper oxide reacts exhausted. Meanwhile, massaoksigen in the copper oxide is the difference between the mass of copper oxide dengantembaga.

The mass of copper in copper oxide is equal to the mass of copper before the heatingconsidering That React perfectly all copper. Whereas the mass of oxygen in copper oxide is thedifference the between the mass of copper oxide and copper

From his observation on mass proportion, Proust declared that the mass of each element which formed a compound has a definite proportion. It is called the law of definite proportion.

By using that law, we can predict the mass of element reacted, the mass of element left, and themass of   the product.

 

 

3. The couple proportions law of oxygen gas and nitrogen gas can react to form more than one compound of nitrogen oxides. Based on the similarity of atomic oxygen and nitrogen, nitrogen oxide compounds can be grouped as follows

Oxygen and nitrogen gas can react to form more than one of nitrogen oxides. They are grouped as shown below The facts obtained show that when two elements can membentuklebih of one compound, and the mass of one element of the amount fixed, perbandinganmassa other elements will be compared as simple integers. Evidence is diamatipertama times by John
D
Alton and known by the name ganda.Sebenarnya comparative law, law of multiple comparisons is the development of atomic theory
D
altom, ie the atoms combine to form compounds, with the numbers and perbandinganyang round and simple The facts obtained PROVE That Pls two elements can form more than one compounds, and mass of one of its elements is constant, comparison of the other element Will be asimple mass ratio. It is first observed by John Dalton and Called as the couple proportions law. Actually, the couple proportions law is developes from Dalton atomic theory, that is if 2elements are Able to form more than one compound, in the which the mass of one of its elements isconstant, the proportion of other mass element has a simple ratio. If the weight of the composition of each pair of elements that can form more than one compound is known, we can use the law of multiple comparisons to determine the chemical formula of the compounds that terbentuk.If the weight composition of each pair can form more than one known compound, wecan use the Couple proportions law to determine the chemical formula of the product compounds.

 

Chemical Reaction

The chemical reaction is a natural process that always results antarubahan chemical compounds. [1] The compounds or compounds involved early in the reaction is referred to as reactants. Chemical reactions are usually characterized by a chemical change, and will result in one or more products which typically have characteristics different from the reactants. Classically, chemical reactions involve changes involving the movement of electrons in the formation and breaking of chemical bonds, although the general concept is basically a chemical reaction can also be applied to the transformation of elementary particles such as in nuclear reactions.Reactions with different chemical used in chemical synthesis to produce the desired compounds. In biochemistry, series of chemical reactions that are catalyzed by enzymes form metabolic trajectory, in which the synthesis and decomposition is usually not possible in the cell do.grouping of chemical reactions
The diversity of chemical reactions and approaches undertaken in the study resulted in the number of ways to classify these reactions, which often overlap. Below are examples of classification of chemical reactions that are usually used.Isomerization, in which chemical compounds undergo structural rearrangement without any change in its atomic kompoasisiDirect combination or synthesis, in which two or more elements or compounds unite to form a complex product:N2 + 3 H2 → 2 NH3Chemical decomposition or analysis, in which a compound is broken down into smaller compounds that:2 H2O → 2 H2 + O2Single replacement or substitution, characterized by an element is replaced by a more reactive element:2 Na (s) + 2 HCl (aq) → 2 NaCl (aq) + H2 (g)Metathesis or double replacement reaction, two compounds which change each other ions or bonds to form different compounds:NaCl (aq) + AgNO3 (aq) → NaNO3 (aq) + AgCl (s)Acid-base reaction, a reaction widely between the acid with a base. It has various definitions depending on the acid-base concept is used. Some of the most common definitions are:Arrhenius definition: acids dissociate in water releasing H3O + ions; bases dissociate in water releasing OH-ions.Brønsted-Lowry definition: Acids are proton donors (H +) donors; base is the recipient (acceptor) protons. Surrounding the Arrhenius definition.Lewis definition: Acids are electron pair acceptors; bases are electron pair donors. This definition encompasses Brønsted-Lowry definition.Redox reactions, in which there is a change in oxidation number of atoms of compounds that react. This reaction can be interpreted as electron transfer. Examples of redox reactions are:2 S2O32-(aq) + I2 (aq) → S4O62-(aq) + 2 I-(aq)Which one is reduced to I-I2 and S2O32-(thiosulfate anion) is oxidized to S4O62-.Combustion, is a kind of redox reaction in which the materials can be burned to join the elements of an oxidant, usually oxygen, to generate heat and form oxidized products. The term combustion is usually used to refer only to the oxidation of a large scale in the whole molecule. Controlled oxidation at only one single functional group is not included in the combustion process.C10H8 + 12 O2 → 10 CO2 + 4 H2OCH2S + 6 F2 → CF4 + 2 HF + SF6Disproportionation, with one reactant to form two types of products that differ only in oxidation state.2 + → Sn Sn2 + + Sn4Organic reactions, encompassing various types of reactions involving compounds which have carbon as its main element.