Atoms, compounds, reactions between compounds

Atoms

1) As an atom is constituted:

It is formed from a nucleus constituted from nucleoni that is neutrons lacking in loads and having protons ^-19 Coulomb loads positive 10 par to 1,6723 *. At a distance remarkable from the nucleus there are the present electrons in equal number to the proton number and having ^-19 Coulomb loads that is equal but with 10 opposite sign-1,6723 *.

 

2) What is the atomic number:

It is a way in order to classify the 103 various present elements in nature, it corresponds to the proton number and therefore of electrons contained from the atom of the element.

 

3) What is a nuclide:

It is a species constituted from atoms all equal ones between of they, an atom is equal to an other if it has the same one n° of protons and therefore of electrons; it is spoken about species why the atoms can differ for the n° of neutrons.

 

4) What is the isotopes:

They are atoms that have the same proton number and therefore of electrons and therefore the same property chemistries, but a various neutron number.

 

5) Thing indicates the notation :

It indicates the nuclide of Carbon, the numbers have following means to you:

12 is the number of equal mass to the sum of protons and neutrons

6 is the number of the protons or n° atomic that to say it wants.

 

6) What is the chemical unit of mass and to what it serves:

A zero relative one used to the aim is to bring back many calculations decimates them to calculations on entire, it is therefore equal place 1 u.c.m. to 1/12 of the mass total (nucleus and electrons) of isotope of carbon . It is worth therefore 1,66043*10^-24gr.

Its scope is to concur with the chemical one not to deal with the mass of the single atom that is smallest, but to choose the mass of an atom as champion and then to assert that the mass of an other atom is n times greater of the mass of the atom champion. In practical instead using an absolute mass one is used relative mass.

 

7) What is the atomic weight and like it is estimated:

It is the relationship between the mass of the considered element and the chemical unit of mass. In the atom case that posseggano more isotopes add the products of the abundances of every isotope for the respective mass.

 

8) Like measure experimentally the mass of one ione and its nuclide:

Through the mass spectrometer, an instrument in a position to freeing for electronic strafing of a ione of the substance (to the gaseous state) which it comes accelerated through a potential difference them that it removes it from the source and projects it towards a Ionian detector of place to the other extremity of the tube to empty, the employed flight time in order to catch up the detector turns out proporziona them to the mass of the ione, Ionian in particular lighter has Ionian short flight times regarding heavier. The mass of the nuclide is obtained adding to this measured mass the weight of the electron removed to the aim of being able to accelerate the ione.

 

9) Describe the phenomenon of the mass defect:

It consists in the fact that the mass of an atom is not equal to the sum of the masses of constituent particles but inferior. The phenomenon has had to the fact that the constitution of a nucleus determines a tie energy that is that necessary one to unravel the nucleus, and siccome the energy variation is tied to the variation of the mass from the equation of Einstein Dand = Dm*c² achieves some that the mass of the nucleus must diminish.

 

10) Thing indicates the number of Avogadro ? :

Draft of a n° chosen so as to to make to coincide the weight of one size of element with the value of relative the atomic mass. In particular it is contained the carbon atom number in 12gr of nuclide the C whose atomic weight is exactly 12 if reported to the chemical unit of mass. The number ? it has the value of 6,02*10²³.

 

11) What is the size:

It is the matter amount that contains a number of Avogadro of elementary entities.

 

12) What is the grammoatomo:

It is the number of grams of an element that corresponds to the atomic mass of that element (weight of the atom) expressed in u.c.m.

Composed

 

13) What is the molecular weight and like it is estimated:

Molecule of the substance expresses the relationship between the mass of one and the chemical unit of mass. It is given from the sum of all the atomic weights multiplies you of the making elements part of the compound, for you respect to you pedici.

 

14) What is indicated with formal weight:

One uses for those compounds which the ionic compounds where discreet molecules do not exist.

It is the sum of the atomic weights of present atoms in the simpler formula of the compound.

 

15) Enounce the law of the multiple proportions:

If two elements react in order to form more than a compound, the weights of an element that are arranged with a fixed weight of the other element, they are between of they in the relationship of entire and generally small numbers. The atomic reason is that in every molecule as an example 1 atom of C can be legacy to a n° entire of atoms of an other element, not to 3/124 of atom of Or.

 

16) What is the weight equivalent of an element:

It is the amount in grams of the element that reacts with 1 gram of H, is equal to the relationship between the atomic weight of the element and its valence.

 

17) What is the weight equivalent of a compound:

It is the sum of the weights equivalents of the single elements that constitute it.

 

18) As the weight is estimated equivalent of the Mg in the MgO and how much is worth the weight equivalent of the MgO:

It is observed that:

to) From the formula 16gr of Or they react with 24,305gr of Mg

b) It is famous that 1gr of H it reacts with 8gr of Or.

Indians 1gr of H react with 12,152gr of Mg.

The weight equivalent of the MgO is given from the sum of the weights equivalents of the members, that is 8 12,152 = 20,152gr/eq

 

19) Enounce the law of the defined proportions:

In a composed data the constituent elements are always arrange to you in the same proportions in weight, any are the origin and the way of preparation of the compound, I mean to say that in the H water and Or they will be always in the relationship in weight 1: 8.

 

20) What is the minimal formula and like it is estimated:

It is the formula of a compound in which the relationships between forming atoms appear every molecule, such relationships use the smallest possible entire numbers. It is gained calculating the n° of wharves of ciascuna present substance in the compound and poi taking some like reference in order to calculate the relationships.

 

21) What is the molecular formula and like it is estimated:

It is an indicating multiple of the minimal formula how many atoms of ciascuna substance are really present in the molecule.

For ricavarala it is necessary to divide the molecular weight of the molecule in issue for the weight of the minimal formula, gains a coefficient for which all must be multiplied the pedici of the minimal formula obtaining therefore the molecular formula.

 

22) Which it is the property of the equivalent weight in the reactions:

It uses the law of the multiple proportions to the aim to gain relationships pondera them between others the elements all bases to you on the consideration that a whichever number of equivalents of an element reacts with the same one n° of equivalents of any element.

Reactions chemistries

23) Enounce the law of the conservation of the masses:

The sum of the masses of the put substances to react is equal to the sum of the masses of the reaction products.

 

24) Which are the characteristics of one corrected chemical equation:

to) n° the total of atoms of every element it must be the same one in the 2 members of the equation.

b) it loads electrical worker total with the contained substances in the 2 members must be equal.

c) Must be used the shape with the minimums possible stoichiometric coefficients.

 

25) Which it is the limiting reagent if I have 1 size of Cu, 1 size of MnO₄ and 20 wharves of been involvedH₃Or in the reaction:

5 Cu 2 MnO₄ 16 H₃Or 5® 2Cu ² 24Mn ² H₂Or

I divide for 5 the reagents: Cu (2/5) MnO₄ (16/5) H₃Or

and I observe that for with n wharves of Cu wharves of MnO ₄ thattherefore is in excess and n*16/5 wharves of H ₃ Or reactn*2/5 that therefore is in excess, therefore Cu are the limiting reagent.

 

26) Which method is used for the balance of reactions of association, dissosciation and exchange:

A letter to every incognito stoichiometric coefficient is assigned and a system is written on these incognito, from then an arbitrary value to one of they and the others are gained.

 

27) Write the reaction of combustion of CH₄ :

₂CH ₄ 2Or ® CO₂ 2H₂Or

 

28) What is the elettronegatività of an atom:

Part of one is the ability to a making atom molecule to attract to himself tie electrons.

In every period it increases approaching itself 7° the group while it decreases to increasing of the atomic number

 

29) What is the number of oxidation of an element:

The n° of oxidation of an atom in a molecule it is the hypothetical charge electrical worker who the atom would have if the tie electrons were assign you to the elettronegativo atom.

 

30) one Can same element have more n.o.:

, the fulcrum of the usefullness of n.o. in how much an element in a composed data is this has a solo n.o. but in an other compound it can adequately have a various one n.o. to the n° of ties that form.

It is particularly useful in order to understand in a reaction which elements yields electrons and which instead acquire them, detention remaining that totally n° of yielded electrons a species must be equal to the n° of electrons acquires to you from an other species or same in the case of one the reaction of disproporzione.

 

31) Calculate the n.o. of CrO₄^2- :

x 4 * (-2) = -2

 

32) How much is worth the n.o. of Or:

It is worth -2 for all the compounds in which oxygen legacy to atoms elettronegati that is all to you is found less except Or and F.

That is to indicate that in all these compounds, Or pu² ridursi acquiring 2 electrons.

 

33) How much is worth the n.o of the H:

It is worth 1 for all the compounds in which legacy to atoms elettronegati to you is found more, that is all to exception of the metals and H.

That is to indicate that in all these cases the H pu² to oxidize itself yielding an electron.

Tasks as an example to the tie with Or, in H₂Or. Or that it is the elettronegativo attracts to himself the doppietti electronic of tie and therefore H loses 1 electron and its it loads is that one of one ione positive.

 

34) Which it is the positive maximum n.o. that an element can have:

The positive maximum n.o. coincides with the electron number that the atom must lose in order to empty the more external shell.

 

35) Which negative is the minimum n.o. that an element can have:

The minimum n.o. negative coincides with the electron number that the atom must acquire in order to complete the more external shell.

 

36) As the reactions based on the variation of the n° are classified of oxidation:

to) reactions in which n.o. of the every not varied present substance (reactions of neutralization or salificazione, and exchange).

b) reactions in which n.o. one or more substances varied (ossidoriduzione reactions and the dismutazione reactions).

 

37) practical Criteria us for the resolution of ossidoriduzione reactions:

to) writing the numbers of oxidation to the aim to characterize which substances they are oxidized and which instead are reduced

b) in ambient acid

To write the semireaction of reduction writing to sx and dx the Ionian correspondents lacking in stoichiometric coefficients and every ione one single time. To balance eventual oxygens in excess to 1° the member with H₂Or to 2° the member, to balance hour the eventual excess of H to 2° the member with H to 1° the member, to distribute a load finally electron being varied the n°.

in basic atmosphere

To write the semireaction of reduction writing to sx and dx the Ionian correspondents lacking in stoichiometric coefficients and every ione one single time. To balance eventual oxygens in excess to 1° the member with OH^- to 2° the member, to balance hour the eventual excess of H to 2° the member with H₂O to 1° the member, to verify the balance of the masses, to distribute a load finally electron being varied the n°.

c) to write the semireaction of oxidation and to balance it analogous.

d) to add the two semireactions being carried out the m.c.m. of electrons so that it loads total he is equal to the 2 members.

and) to carry out eventual simplifications.

f) to associate the Ionian ones to the respective one composed gaining of the just stechiometria. In this phase it is from noticing that if were H₃Or in the reaction to balance, and in the balance in 5 as an example to you ionic shape they are characterizes H the passage in molecular shape previews thatthe 5H₃ Or becomes 5 and in order to compensate H₂Or in such a way inserted, is necessary to add of as many to already present waters to the other member.

 

38) As it is behaved to us if in a reaction redox 2 elements reduce themselves (they oxidize):

The 2 semireactions are written singularly, they are balanced and then comprised electrons are added to form one only semireaction of reduction.

 

39) As it is behaved to us when in the description of an exercise one says to us that composed determining is indissociato:

It is necessary to carry out the balance of the reaction writing semireactions in which appears the compound and not a hypothetical one ione that the text says to us that does not exist.

 

40) Describe the method of the Ionian ones forms them for the reactions to dry:

The simple semireactions of oxidation and reduction are written considering the single element that oxidizes itself or reduces and not the group in which it is inserted, in such a way it is not necessary to balance with H₂Or or H₃Or or OH^- . To the term but it is necessary to complete the balance for the species not been involved in some of the 2 semireactions.

 

41) Define the weight equivalent of an acid:

It is the amount in grams of an acid that can donate a size of protons to a base, is estimated dividend n° the PM of acid for the n° of protons that it can yield.

 

42) Define the weight equivalent of one base:

It is the amount in grams of a base that can accept a proton size from an acid, is estimated dividend the PM of the base for the n° of protons that it can accept from an acid.

 

43) Define the weight equivalent of knows them:

It is the mass of the size uniform for loads total with the cationi (or of present anions in the formula of it knows them).

Dividend is estimated the PM of knows them for the product between the n° of wharves of cationi that are formed for the n° of associated positive charges to every size, as an example for Cu(SO₄) taking as reference Cu² we have that PE = PM/(1*2). Such value identical if is calculated regarding the anion (KNOWS₄)^2- .

 

44) Define the weight equivalent of one oxidating substance or reducing:

It is the amount in grams of substance that supplies an electron size or reacts with an electron size, is estimated dividend the PM of the element for the n° of electrons that yields or acquires.

 

45) To what it serves conecetto of equivalent in the reactions between acids and the said bases of salificazione:

Equal numbers of equivalents of every base or every acid are neutralized exactly between of they and produce the same number of equivalents of know them.