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I'm not an expert teacher or lecturer of chemistry. I was only a student from SMA NEGERI 15 SURABAYA who had been one of the Bronze Medalist Participants of Olimpiade Sains Nasional X (2011) of Chemistry In Manado, North Sulawesi, 11 - 16 September 2011 and graduated in 2012. Now, I'm studying at Universitas Airlangga in Surabaya, Indonesia. I do love chemistry and I would like to help them who had difficulties in studying chemistry. That's why, please understand me if you found some misconcepts in my entries. Suggestions are always necessary in order to develop this blog. And I'm sorry because my English isn't so well.

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Wednesday, June 13, 2012

SNMPTN Kimia 2012 Kode 132 (Translated in English)

31. A compound with its Mr = 80 consists of 40% mass of element X (Ar = 32) and  60% mass of element Y (Ar = 16). The molecular formula of this compound is...

We already have the mass percentage of each element. So we just have to determine how many moles of X in the compound.

 

Assume the compound has molecular formula of XaYb. We already got the value of a (a = 1). Now we have to determine the value of b.

Mr of Y = Mr - Ar of X
Mr of Y = 80 - 32
Mr of Y = 48

Ar of Y = 16 so that the value of b = 3. The answer is XY3

32. The substitution reaction of 1-chlorobutane with methoxide ion will produce...

The mechanism reaction of this reaction is Bimolecular Substitution Reaction (SN2). See the figure as follows:


So the answer is methyl n-butyl ether.

33. Electrolysis of AgNO3 solution produces 10.8 gram of silver precipitates (Ar = 108). If the same electricity current is used to reduce MnO4- to Mn2+ so, the total amount of mol of Mn2+ which is produced is...

From the data above, the total amount of Ag = 0,10 mol. Ag+ needs 1 electron to reduce it to form Ag so that the total amount of electron needed is 0,10 mol.

MnO4- needs 5 electrons to reduce it to Mn2+. The mol of electron is 0,10 mol so that we need 0,02 mol of to MnO4- produce 0,02 mol of Mn2+.

34. The following table shoes the data of combustion enthalpy of five kinds of fuel:


The combustion of 1 gram of each fuel which produces the highest energy is..

You know this formula? q = dH n ?
Well, use this to answer this question and you'll get that Hydrogen is the fuel that produces the highest energy.

35. 6.2 grams of C22H46 (Mr = 310) is dissolved into 77 grams of CCl4 (Mr = 154). If the vapor pressure of pure CCl4 at 23 oC is 0.150 atm, the decreasing of solution vapor pressure is...




36. Known the Kb of NH3 is 2.0 x 10-5. The pH value of 0.008 M NH4Cl solution is...


37.  An alloy which is consisted of 80% Zn (Ar = 65) and 20% Cu (Ar = 63,5) is reacted perfectly with diluted HCl and produces 2.24 L of H2 gas at STP. The mass of this alloy is...

Cu doesn't react with diluted HCl because it's too inert for this reaction so that the hydrogen gas is produced by the reaction of Zn with HCl. From the balanced chemical equation of the reaction between Zn and HCl, we can conclude that the mol ratio of Zn and H2 is 1 : 1.

Mol of H2 is 0.1 mol at STP so that the mol of Zn is 0.1 mol
Mass of Zn = 0.1 x 65 = 6.5 grams. (80% of the alloy)

Mass of the alloy (100%) is 8.125 grams = 8.13 grams.

38. 2.5 mol of NOCl fills a 1L closed vessel at 800 oC. After the equilibrium is reached, 60% of NOCl is dissociated as shows on the following reaction:


The value of Kc for this equilibrium reaction is...


39. The right order of the radius of Oxygen, Sodium, Chlorine, and Potassium atom is . . .

Just see your periodic table and you will find that K > Na > Cl > O

40. In a closed vessel, the dissociation of sulfuryl chloride (SO2Cl2) is happened as shows by the following reaction:


The kinetic rate law of this reaction is r = k[SO2Cl2]. The right statement of this reaction is...

The concentration of SO2Cl2 will be decreased with the rate = r M/s.
The concentration of SO2 will be increased with the rate = r M/s.
The concentration of Cl2 will be increased with the rate = r M/s.

41.  In a reaction with NH3, BH3 is the Lewis Base.
BECAUSE
Lewis Acid is a chemical species that accepts electron pair in a chemical reaction.

BH3 is a Lewis Acid, which is a chemical species that accepts electron pair in a chemical reaction. 

42. A polypeptide which is only consisted of the monomer of Aspartic Acid is soluble in water.

BECAUSE

The side chain of this poly-aspartic acid can form the hydrogen bond with water molecules.

Polypeptide is a natural polymer that is formed by the condensation reaction between the amines and carboxylic acid groups of the monomers. From the picture above, we can conclude that in this poly-aspartic acid, there will be so many carboxylic acid groups from the side chain which make this polypeptide a polar polypeptide so that it is soluble in water and of course the carboxylic acid groups can form the hydrogen bond with water molecules.

43. Known H (Z = 1), N (Z = 7), and F (Z = 9). The right statement(s) for NH3 and NF3 molecules is(are)...

NH3 can form the hydrogen bond while NF3 couldn't form it so that the boiling point of NH3 > NF3.

The electronegativity of F > H so that the distribution of electron in NF3 will tend to the F atoms while in NH3 will tend to the N atom so that the basidity of NH3 > NF3.

Of course the total amount of lone pair of electrons in NF3 > NH3.

The geometry of NH3 molecule is the same as NF3.

44. Known:
Eo Sn2+ | Sn = -0.14 V
Eo Fe3+ | Fe = -0.04 V

At standard condition, the right statement(s) for the reaction of:

 
is..

Arrange the two half-reaction above and you'll find that the Eo cell value of this reaction is +0.10 V (Which means this is a spontaneous reaction). We can conclude that this reaction needs 6 electrons and Fe3+ is the oxidation agent.


45. For the equilibrium reaction of the forming of [FeCl]2+ as shows with the reaction below:




The concentration of will [FeCl]2+ increase if...

With addition of Fe(NO3)3 or AgNO3 the concentration of [FeCl]2+ will increase. The increase in temperature will make the equilibrium shift to right but addition of catalyst won't affect this system.


Source:
Direktorat Jenderal Pendidikan Tinggi
SNMPTN Jalur Tulis Program IPA Kode 132 Tahun 2012
 

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