Elucidation of the structure of the periodic table The number of electron shells an atom determines the atomic period. Each skin has a subshell, which is loaded according to the following sequence, along with increasing atomic number: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 8s 5g 6f 7d 7P 8p
Senin, 21 November 2011
MID SEMESTR TEST
COURSE :BASIC CHEMISTRY
LECTURER:DR.SYAMSURIZAL
1.Pure substance X is solid at room temperature.if the substance is heated to 230 degree celcius is melted gradually.if then cooled to room temperature,the liquid can not be frozen
a. Is it pssible 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 the liquid is an element,based on the information provided?
2.When a candle that weighs 10 gram is burned in xygen,carbon dioxide and water vapor formed by combustion the weight more than 10 gram.Was this case match with the law of conservation of mass.Explain it!
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.
4.After Mendeleev compiled the periodic table ,he concluded that the atomic weights of certain elements was wrong ruling ,and this conclusion was apparently correct.How Mendeleev was able to predict that several atomic weights were wrong?Why his predictions are not always right.Explain !
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.
Langganan:
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BalasHapus2.
3.Incomplete combustion, the reactant burns in oxygen, producing a limited number of products. When a hydrocarbon burns in oxygen, the reaction will only yield carbon dioxide and water. When elements are burned, the products are primarily the most common oxides. Carbon will yield carbon dioxide, nitrogen will yield nitrogen dioxide, sulfur will yield sulfur dioxide, and iron will yield iron(III) oxide.
ncomplete combustion will only occur when there is not enough oxygen to allow the fuel to react completely to produce carbon dioxide and water. It also happens when the combustion is quenched by a heat sink such as a solid surface or flame trap.
For most fuels, such as diesel oil, coal or wood, pyrolysis occurs before combustion. In incomplete combustion, products of pyrolysis remain unburnt and contaminate the smoke with noxious particulate matter and gases. Partially oxidized compounds are also a concern; partial oxidation of ethanol can produce harmful acetaldehyde, and carbon can produce toxic carbon monoxide.
4.Mendeleev laid out all the known elements in order of 'atomic weight' (what we know call relative atomic mass, Ar) except for several examples like tellurium (Te, Ar = 127.60) and iodine (I, Ar = 126.90) whose order he reversed because chemically they seemed to be in the wrong vertical column! Smart thinking!
Argon (Ar, Ar = 39.95) and potassium (K, Ar = 39.10) is the 2nd example, but that was not a problem for chemists at the time, because the Group 0 Noble Gases hadn't been discovered by then!
These 'anomalies' in the order of 'atomic weights' are explained by the existence of isotopes which were discovered ~1916 and the neutron finally characterised in 1932.
Isotopes of elements are atoms of the same proton number with different numbers of neutrons, hence atoms of the same element with different mass numbers.
The most abundant stable isotope of potassium is 39K, and that of argon is 40Ar, hence the anomaly.
Naturally occurring iodine is 100% 127I, but tellurium has a range of isotopic masses from 120Te to 130Te but more the heavier isotopes are more abundant than the lighter isotopes.
By 1869, Mendeleev and Lothar Meyer had an advantage over Newlands because there was an increased number of known elements and hence 'groups' of similar elements were becoming more clearly defined.
Mendeleev used a double column approach which is NOT incorrect, i.e. a sort of group xA and xB classification. This is due to the 'insert' of transition metals, some of whom show chemical similarities to the vertical 'groups'. We now recognise theses dual columns as
His 'presentation' was sufficiently accurate to predict missing elements and their properties * e.g. germanium (Ge) below silicon (Si) and above tin (Sn) in Group IV and Mendeleev is rightly called the 'father of the modern Periodic Table'.
5.HgNO3 + 2 HCl → HgCl2 + H2O + NO2
Mercuric chloride is obtained by the action of chlorine on mercury or mercury(I) chloride, by the addition of hydrochloric acid to a hot, concentrated solution of mercury(I) compounds such as the nitrate