why are the Acidity increases going down a row of the periodic table?
answer : according my opinion and acidity increases going left to right (because more electronegative atoms can stabilize the negative charge on the anion) and increases going down because the larger the atom the better it can delocalize the negative charge.
Nucleophicity and basicitiy tend to be similar to each other but opposite to electrongegativity trends. Nucleophicity increases going left across a period and up a group.
The Electron affinity of a molecule or atom is the energy change when an electron is added to the neutral atom to form a negative ion. This property can only be measured in an atom in gaseous state.
X + e− → X−
The electron affinity, Eea, is defined as positive when the resulting ion has a lower energy, i.e. it is an exothermic process that releases energy:
Eea = Einitial − Efinal
Alternatively, electron affinity is often described as the amount of energy required to detach an electron from a singly charged negative ion[1], i.e. the energy change for the process
X− → X + e−
A molecule or atom that has a positive electron affinity is often called an electron acceptor and may undergo charge-transfer reactions.
Contents
Although Eea varies greatly across the periodic table, some patterns emerge. Generally, nonmetals have more positive Eea than metals. Atoms whose anions are more stable than neutral atoms have a greater Eea. Chlorine most strongly attracts extra electrons; mercury most weakly attracts an extra electron. The electron affinities of the noble gases have not been conclusively measured, so they may or may not have slightly negative values.
Eea generally increases across a period (row) in the periodic table. This is caused by the filling of the valence shell of the atom; a group 7A atom releases more energy than a group 1A atom on gaining an electron because it obtains a filled valence shell and therefore is more stable.
A trend of decreasing Eea going down the groups in the periodic table would be expected. The additional electron will be entering an orbital farther away from the nucleus, and thus would experience a lesser effective nuclear charge. However, a clear counterexample to this trend can be found in group 2A, and this trend only applies to group 1A atoms. Electron affinity follows the trend of electronegativity. Fluorine (F) has a higher electron affinity than oxygen and so on.
the strenght of acid and base
The order of acid strength solution of HCl, HClO, HClO2, HClO3, and HClO4
How you can indulge in acid strength of the compounds of HCl, HClO, HClO2, HClO3, and HClO4? What parameters you can use to measure the degree of acidity of these compounds?
Trend strength above acid can be determined with the following parameters:
Acid strength will be greater with increasing number of oxygen atoms attached to the center.
Acid strength will be even greater with the increasing size of the central atom oxidation number (in kasusini the Cl atom)
By using the above parameters of course you can sort the acid strength of the above compounds is not it? To know "Kenapanya" then you can read the following description and Structure acids are:
Qualitative explanation
According to the Bronsted-Lowry acid is a proton donor, so the acid strength is determined by how easily a species to donate protons. The easier a proton donating species, then the acid will become stronger as well as vice versa. Easy or not an acid species to donate protons can be seen from how much the price of Ka and how much acid is ionized in solution.
We note compounds HClO, HClO2, HClO3, and HClO4 are ionized in water by reaction as follows:
HClO + H2O -> H3O + + clo-
HClO2 + H2O -> H3O + + ClO2-
HClO3 + H2O -> H3O + + ClO3-
HClO4 + H2O -> H3O + + ClO4-
The greater the number of ionized species, the amino acid will be stronger and vice versa. How can we determine the above acids, which one would ionized perfect and which are ionized in part to our use in determining the strength of acid?
How you can use is to determine the stability of residual acid anions in the solution of anion clo-, ClO2-, ClO3-, and ClO4-. The more stable anionnya the more acidic ionized and automatically stronger acidic.
How you can determine the stability of these anions? The answer is by seeing how these anions distribute the negative charge (or in other words look at the structure resonance). The greater the amount of oxygen atoms above the more stable the anion, because the more the number of oxygen atoms that can accept the negative charge distribution, this also means that the anion has a lot of resonance structures.
As an illustration, we carry a lighter load with 4 people instead of carrying the same load with two people. For the above case let's just bebanya is a negative charge, ClO4-ions can distribute the negative charge on the 4 oxygen atoms while the ion-ClO3 can only distribute the negative charge on the 3 oxygen atoms, two to ClO2-ion, and unfortunately ion-CLO can not distribute content negative, so that ClO4-anions is much more stable than the other.
Thus the above sequence is a stable anion-ClO4> ClO3-> ClO2-> clo-. Remember the more stable anion which means more acid is ionized so that the greater acid strength by sebabitu acid sequence of the greatest strengths is HClO4> HClO3> HClO2> HClO.
By looking at the price of Ka / pKa
Price pKa of the acid above is:
HCl pKa = -8
HClO pKa = 7.53
HClO2 pKa = 2
pKa HClO3 = -1
pKa HClO4 = -10
The lower the price pKa the stronger acid, so according to the price above the acid strength of the largest are HClO4> HCl> HClO3> HClO2> HClO. From the data above the price pKa HCl, HClO3, and HClO4 is negative because these acids are strong acids. HCl strength is almost the same can be said with HClO4, this possibility is because HCl in the form of solution [HCl (aq)] as an ionic compound is so easy to let go of its protons HCl. (Gaseous HCl is a weak acid because the H-Cl bond in the form of gas is covalent).
Note:
HCl in the first discussion I was not included because we can not compare the strength of hydrochloric acid in kualittaif with HClO, HClO2, HClO3, and HClO4 is an oxy acid. We are more easily compare the strength of acidity of HCl is qualitatively with HI, HBr, or HF.
posted by : Name : vebria Ardina
NIM : RSA1C110020
class : ISSTE of Chemistry
How you can indulge in acid strength of the compounds of HCl, HClO, HClO2, HClO3, and HClO4? What parameters you can use to measure the degree of acidity of these compounds?
Trend strength above acid can be determined with the following parameters:
Acid strength will be greater with increasing number of oxygen atoms attached to the center.
Acid strength will be even greater with the increasing size of the central atom oxidation number (in kasusini the Cl atom)
By using the above parameters of course you can sort the acid strength of the above compounds is not it? To know "Kenapanya" then you can read the following description and Structure acids are:
Qualitative explanation
According to the Bronsted-Lowry acid is a proton donor, so the acid strength is determined by how easily a species to donate protons. The easier a proton donating species, then the acid will become stronger as well as vice versa. Easy or not an acid species to donate protons can be seen from how much the price of Ka and how much acid is ionized in solution.
We note compounds HClO, HClO2, HClO3, and HClO4 are ionized in water by reaction as follows:
HClO + H2O -> H3O + + clo-
HClO2 + H2O -> H3O + + ClO2-
HClO3 + H2O -> H3O + + ClO3-
HClO4 + H2O -> H3O + + ClO4-
The greater the number of ionized species, the amino acid will be stronger and vice versa. How can we determine the above acids, which one would ionized perfect and which are ionized in part to our use in determining the strength of acid?
How you can use is to determine the stability of residual acid anions in the solution of anion clo-, ClO2-, ClO3-, and ClO4-. The more stable anionnya the more acidic ionized and automatically stronger acidic.
How you can determine the stability of these anions? The answer is by seeing how these anions distribute the negative charge (or in other words look at the structure resonance). The greater the amount of oxygen atoms above the more stable the anion, because the more the number of oxygen atoms that can accept the negative charge distribution, this also means that the anion has a lot of resonance structures.
As an illustration, we carry a lighter load with 4 people instead of carrying the same load with two people. For the above case let's just bebanya is a negative charge, ClO4-ions can distribute the negative charge on the 4 oxygen atoms while the ion-ClO3 can only distribute the negative charge on the 3 oxygen atoms, two to ClO2-ion, and unfortunately ion-CLO can not distribute content negative, so that ClO4-anions is much more stable than the other.
Thus the above sequence is a stable anion-ClO4> ClO3-> ClO2-> clo-. Remember the more stable anion which means more acid is ionized so that the greater acid strength by sebabitu acid sequence of the greatest strengths is HClO4> HClO3> HClO2> HClO.
By looking at the price of Ka / pKa
Price pKa of the acid above is:
HCl pKa = -8
HClO pKa = 7.53
HClO2 pKa = 2
pKa HClO3 = -1
pKa HClO4 = -10
The lower the price pKa the stronger acid, so according to the price above the acid strength of the largest are HClO4> HCl> HClO3> HClO2> HClO. From the data above the price pKa HCl, HClO3, and HClO4 is negative because these acids are strong acids. HCl strength is almost the same can be said with HClO4, this possibility is because HCl in the form of solution [HCl (aq)] as an ionic compound is so easy to let go of its protons HCl. (Gaseous HCl is a weak acid because the H-Cl bond in the form of gas is covalent).
Note:
HCl in the first discussion I was not included because we can not compare the strength of hydrochloric acid in kualittaif with HClO, HClO2, HClO3, and HClO4 is an oxy acid. We are more easily compare the strength of acidity of HCl is qualitatively with HI, HBr, or HF.
posted by : Name : vebria Ardina
NIM : RSA1C110020
class : ISSTE of Chemistry
rasa asin pada air laut
Bagaimanakah rasa air laut?? ASIN,, Kenapa rasa air laut asin?? Darimanakah rasa asin itu??
Merasa bingung khan?? Mari kita bicarakan bersama....
Laut adalah kumpulan air asin yang luas dan berhubungan dengan samudra.
Penyebab rasa asin itu adalah garam-garaman yang terkandung di dalam air laut. Air di laut merupakan campuran dari 96,5% air murni dan 3,5% material lainnya seperti garam-garaman, gas-gas terlarut, bahan-bahan organik dan partikel-partikel tak terlarut. Sifat-sifat fisis utama air laut ditentukan oleh 96,5% air murni.Jumlah dari seluruh garam-garaman dalam gram pada setiap kilogram air laut disebut salinitas. Garam adalah senyawa kimia yang terdiri dari dua bagian yang bermuatan positif dan bermuatan negatif yang keduanya saling tarik menarik sehingga membentuk “garam” (bagian yang bermuatan positif dan negatif ini disebut ION). Unsur Garam-garaman utama yang terdapat dalam air laut adalah klorida (55%), natrium (31%), sulfat (8%), magnesium (4%), kalsium (1%), potasium (1%) dan sisanya (kurang dari 1%) teridiri dari bikarbonat, bromida, asam borak, strontium dan florida.
Darimanakah asalnya garam-garamam tersebut??
Sumber utama garam-garaman di laut adalah pelapukan batuan di darat, gas-gas vulkanik dan sirkulasi lubang-lubang hidrotermal (hydrothermal vents) di laut dalam. Bagaimana prosesnya? Kita tahu bahwa laut adalah tempat berkumpulnya semua air; air dari rumah, selokan, sungai, semua air, termasuk air hujan. Kesemuanya mengalir menuju laut, sambil “mencuci” batuan, tanah, semua benda yang dilewatinya, sambil membawa juga ion-ion tadi (semua terjadi dalam proses hidrologis). Belum lagi peristiwa alam seperti letusan gunung api baik yang di daratan maupun di lautan, semua memberi kandungan khlor yang berlimpah bagi lautan. Proses ini terjadi secara terus menerus selama milyaran tahun.
Laut, menurut sejarahnya, terbentuk 4,4 milyar tahun yang lalu, dimana awalnya bersifat sangat asam dengan air yang mendidih (dengan suhu sekitar 100°C) karena panasnya Bumi pada saat itu. Asamnya air laut terjadi karena saat itu atmosfir Bumi dipenuhi oleh Karbondioksida. Keasaman air inilah yang menyebabkan tingginya pelapukan yang terjadi yang menghasilkan garam-garaman yang menyebabkan air laut menjadi asin seperti sekarang ini.
Merasa bingung khan?? Mari kita bicarakan bersama....
Laut adalah kumpulan air asin yang luas dan berhubungan dengan samudra.
Penyebab rasa asin itu adalah garam-garaman yang terkandung di dalam air laut. Air di laut merupakan campuran dari 96,5% air murni dan 3,5% material lainnya seperti garam-garaman, gas-gas terlarut, bahan-bahan organik dan partikel-partikel tak terlarut. Sifat-sifat fisis utama air laut ditentukan oleh 96,5% air murni.Jumlah dari seluruh garam-garaman dalam gram pada setiap kilogram air laut disebut salinitas. Garam adalah senyawa kimia yang terdiri dari dua bagian yang bermuatan positif dan bermuatan negatif yang keduanya saling tarik menarik sehingga membentuk “garam” (bagian yang bermuatan positif dan negatif ini disebut ION). Unsur Garam-garaman utama yang terdapat dalam air laut adalah klorida (55%), natrium (31%), sulfat (8%), magnesium (4%), kalsium (1%), potasium (1%) dan sisanya (kurang dari 1%) teridiri dari bikarbonat, bromida, asam borak, strontium dan florida.
Darimanakah asalnya garam-garamam tersebut??
Sumber utama garam-garaman di laut adalah pelapukan batuan di darat, gas-gas vulkanik dan sirkulasi lubang-lubang hidrotermal (hydrothermal vents) di laut dalam. Bagaimana prosesnya? Kita tahu bahwa laut adalah tempat berkumpulnya semua air; air dari rumah, selokan, sungai, semua air, termasuk air hujan. Kesemuanya mengalir menuju laut, sambil “mencuci” batuan, tanah, semua benda yang dilewatinya, sambil membawa juga ion-ion tadi (semua terjadi dalam proses hidrologis). Belum lagi peristiwa alam seperti letusan gunung api baik yang di daratan maupun di lautan, semua memberi kandungan khlor yang berlimpah bagi lautan. Proses ini terjadi secara terus menerus selama milyaran tahun.
Laut, menurut sejarahnya, terbentuk 4,4 milyar tahun yang lalu, dimana awalnya bersifat sangat asam dengan air yang mendidih (dengan suhu sekitar 100°C) karena panasnya Bumi pada saat itu. Asamnya air laut terjadi karena saat itu atmosfir Bumi dipenuhi oleh Karbondioksida. Keasaman air inilah yang menyebabkan tingginya pelapukan yang terjadi yang menghasilkan garam-garaman yang menyebabkan air laut menjadi asin seperti sekarang ini.
why is the water droplets round?
Why is the water droplets round?
Perhaps these questions are rarely ignored by many. here I will try to uncover this mystery. every drop of water falling to the ground or down it must be round. Spherical shape is the shape and tersimpel populous than all existing forms, such as rectangular or triangular. This simple form makes the water droplets become unstable, and therefore all forms of the elements or anything else always has a tendency to form something more stable. Then the wisdom what is hidden behind this phenomenon. as we know that our earth is round, everything is round always familiar to many people, just for example football, basketball, dsb.Kehidupan it's like a round ball and is always spinning, there is sometimes above and sometimes under . This situation caused the man to do ever mnyombongkan yourself for what has he got, because God was the one who has the truth. This life is also always lead to stability and equilibrium. Everything in this universe will be in equilibrium, namely death. therefore we sembagai a servant who is weak, it should always be ready with his arrival, and always our position to form a more stable from day to day. as shown by the noble gas elements that have remarkable stability. If the element is stable by imitating the number of electrons that are owned by the noble gases, why we do not do it. Indeed the rules created are not made to narrow down / restrain us, but to help us later.
Perhaps these questions are rarely ignored by many. here I will try to uncover this mystery. every drop of water falling to the ground or down it must be round. Spherical shape is the shape and tersimpel populous than all existing forms, such as rectangular or triangular. This simple form makes the water droplets become unstable, and therefore all forms of the elements or anything else always has a tendency to form something more stable. Then the wisdom what is hidden behind this phenomenon. as we know that our earth is round, everything is round always familiar to many people, just for example football, basketball, dsb.Kehidupan it's like a round ball and is always spinning, there is sometimes above and sometimes under . This situation caused the man to do ever mnyombongkan yourself for what has he got, because God was the one who has the truth. This life is also always lead to stability and equilibrium. Everything in this universe will be in equilibrium, namely death. therefore we sembagai a servant who is weak, it should always be ready with his arrival, and always our position to form a more stable from day to day. as shown by the noble gas elements that have remarkable stability. If the element is stable by imitating the number of electrons that are owned by the noble gases, why we do not do it. Indeed the rules created are not made to narrow down / restrain us, but to help us later.
An introduction to organic reaction
In this lessonWe learn about an introduction to organic reaction : Acid and Bases, and I less understood about
Question : What is relationship between structur and acidity?
According My opinion The strength of an acid depends on the extent to which a proton can be separated from it and transferred to a base.Breaking a bond to the proton Þ the strength of the bond to the proton is the dominating effect.
The Acidity of Carboxylic Acids
Carboxylic acids are much more acidic than the corresponding alcohols: pKas for R–COOH are in the range of 3-5;.pKas for R–OH are in the range of 15-18.
An Explanation Based on Resonance Effects
Resonance stabilized acetate anion: The greater stabilization of the carboxylate anion (relative to the acid) lowers the free energy of the anion and thereby decreases the positive free-energy change required for the ionization. Any factor that makes the free-energy change for the ionization of an acid less positive (or more negative) makes the acid stronger.
An Explanation Based on Inductive Effects
The inductive effect of the carbonyl group (C=O group) is responsible for the acidity of carboxylic acids.
Organic Compounds as Bases
An organic compound contains an atom with an unshared electron pair is a potential base. The p bond of an alkene can act as a base.
The Acidity of Carboxylic Acids
Carboxylic acids are much more acidic than the corresponding alcohols: pKas for R–COOH are in the range of 3-5;.pKas for R–OH are in the range of 15-18.
An Explanation Based on Resonance Effects
Resonance stabilized acetate anion: The greater stabilization of the carboxylate anion (relative to the acid) lowers the free energy of the anion and thereby decreases the positive free-energy change required for the ionization. Any factor that makes the free-energy change for the ionization of an acid less positive (or more negative) makes the acid stronger.
An Explanation Based on Inductive Effects
The inductive effect of the carbonyl group (C=O group) is responsible for the acidity of carboxylic acids.
Organic Compounds as Bases
An organic compound contains an atom with an unshared electron pair is a potential base. The p bond of an alkene can act as a base.
Posted by : NAME : VEBRIA ARDINA
NIM : RSA1CI10020
ANGKATAN 2010
CLASS : ISSTE of CHEMISTRY
Alkene
Why are alkenes are relatively stable compounds, but are more reactive than alkanes?
Ethylene (ethene), showing the pi bond in green. 
According my opinion it is because Alkenes are relatively stable compounds, but are more reactive than alkanes due to the presence of a carbon-carbon pi-bond. It is also attributed to the presence of pi-electrons in the molecule. The majority of the reactions of alkenes involve the rupture of this pi bond, forming new single bonds.
Like single covalent bonds, double bonds can be described in terms of overlapping atomic orbitals, except that, unlike a single bond (which consists of a single sigma bond), a carbon-carbon double bond consists of one sigma bond and one pi bond. This double bond is stronger than a single covalent bond (611 kJ/mol for C=C vs. 347 kJ/mol for C—C)[1] and also shorter with an average bond length of 1.33 Angstroms (133 pm).
Each carbon of the double bond uses its three sp² hybrid orbitals to form sigma bonds to three atoms. The unhybridized 2p atomic orbitals, which lie perpendicular to the plane created by the axes of the three sp² hybrid orbitals, combine to form the pi bond. This bond lies outside the main C—C axis, with half of the bond on one side and half on the other.
Rotation about the carbon-carbon double bond is restricted because it involves breaking the pi bond, which requires a large amount of energy (264 kJ/mol in ethylene). As a consequence, substituted alkenes may exist as one of two isomers, called cis or trans isomers. More complex alkenes may be named using the E-Z notation, used to describe molecules having three or four different substituents (side groups). For example, of the isomers of butene, the two methyl groups of (Z)-but-2-ene (aka cis-2-butene) face the same side of the double bond, and in (E)-but2-ene (aka trans-2-butene) the methyl groups face the opposite side. These two isomers of butene are slightly different in their chemical and physical properties.
It is certainly not impossible to twist a double bond. In fact, a 90° twist requires an energy approximately equal to half the strength of a pi bond. The misalignment of the p orbitals is less than expected because pyramidalization takes place (See: pyramidal alkene). trans-Cyclooctene is a stable strained alkene and the orbital misalignment is only 19° with a dihedral angle of 137° (normal 120°) and a degree of pyramidalization of 18°. This explains the dipole moment of 0.8 D for this compound (cis-isomer 0.4 D) where a value of zero is expected.[3] The trans isomer of cycloheptene is only stable at low temperatures.
As predicted by the VSEPR model of electron pair repulsion, the molecular geometry of alkenes includes bond angles about each carbon in a double bond of about 120°. The angle may vary because of steric strain introduced by nonbonded interactions created by functional groups attached to the carbons of the double bond. For example, the C-C-C bond angle in propylene is 123.9°.
The physical properties of alkenes are comparable with those of alkanes. The physical state depends on molecular mass (gases from ethene to butene - liquids from pentene onwards). The simplest alkenes, ethene, propene and butene are gases. Linear alkenes of approximately five to sixteen carbons are liquids, and higher alkenes are waxy solids.
Alkenes react in many addition reactions, which occur by opening up the double-bond. Most addition reactions to alkenes follow the mechanism of electrophilic addition. Examples of addition reactions are hydrohalogenation, halogenation, halohydrin formation, oxymercuration, hydroboration, dichlorocarbene addition, Simmons-Smith reaction, catalytic hydrogenation, epoxidation, radical polymerization and hydroxylation.Like single covalent bonds, double bonds can be described in terms of overlapping atomic orbitals, except that, unlike a single bond (which consists of a single sigma bond), a carbon-carbon double bond consists of one sigma bond and one pi bond. This double bond is stronger than a single covalent bond (611 kJ/mol for C=C vs. 347 kJ/mol for C—C)[1] and also shorter with an average bond length of 1.33 Angstroms (133 pm).
Each carbon of the double bond uses its three sp² hybrid orbitals to form sigma bonds to three atoms. The unhybridized 2p atomic orbitals, which lie perpendicular to the plane created by the axes of the three sp² hybrid orbitals, combine to form the pi bond. This bond lies outside the main C—C axis, with half of the bond on one side and half on the other.
Rotation about the carbon-carbon double bond is restricted because it involves breaking the pi bond, which requires a large amount of energy (264 kJ/mol in ethylene). As a consequence, substituted alkenes may exist as one of two isomers, called cis or trans isomers. More complex alkenes may be named using the E-Z notation, used to describe molecules having three or four different substituents (side groups). For example, of the isomers of butene, the two methyl groups of (Z)-but-2-ene (aka cis-2-butene) face the same side of the double bond, and in (E)-but2-ene (aka trans-2-butene) the methyl groups face the opposite side. These two isomers of butene are slightly different in their chemical and physical properties.
It is certainly not impossible to twist a double bond. In fact, a 90° twist requires an energy approximately equal to half the strength of a pi bond. The misalignment of the p orbitals is less than expected because pyramidalization takes place (See: pyramidal alkene). trans-Cyclooctene is a stable strained alkene and the orbital misalignment is only 19° with a dihedral angle of 137° (normal 120°) and a degree of pyramidalization of 18°. This explains the dipole moment of 0.8 D for this compound (cis-isomer 0.4 D) where a value of zero is expected.[3] The trans isomer of cycloheptene is only stable at low temperatures.
As predicted by the VSEPR model of electron pair repulsion, the molecular geometry of alkenes includes bond angles about each carbon in a double bond of about 120°. The angle may vary because of steric strain introduced by nonbonded interactions created by functional groups attached to the carbons of the double bond. For example, the C-C-C bond angle in propylene is 123.9°.
The physical properties of alkenes are comparable with those of alkanes. The physical state depends on molecular mass (gases from ethene to butene - liquids from pentene onwards). The simplest alkenes, ethene, propene and butene are gases. Linear alkenes of approximately five to sixteen carbons are liquids, and higher alkenes are waxy solids.
Posted by : NAME : VEBRIA ARDINA
NIM : RSA1C110020
STUDY PROGRAMME : ISSTE OF CHEMISTRY
URL BLOG : http://vebriasanjaya.blogspot.com
Reaction of alkane
Reaction of alkene
1. Why are mostly alkenes compound are inert?
Answer : Because they bonding are saturated (all their rooms is filled by electron).
2. How to break down the bonding of 3, 4, 5 trimethyl nonane into n- butene?
Answer : The first we must find the knots of reactions or centre of reactions agree with the result which we want, like normal butene about less or more than 60 %
H H H H H H H H H
H C C C C C C C C C H
H H CH3 CH3 CH3 H H H H
H H H H H H H H H
H C C C C C C C C C H
H H CH3 CH3 CH3 H H H H
From the node that has the mark on so we can get some stricture of n-butene, namely
H H H
H C C C H
H H CH3
n- butena
H H
H C C H
CH3 CH3
n- butena
H H H H
H C C C C H
H H H H
n- butena
H C C H
CH3 CH3
n- butena
H H H H
H C C C C H
H H H H
n- butena
:
