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| Chemical Reactions | Hoarhak Hoafn'exng |
| A chemical change is called a chemical reaction. In order to communicate with one another about chemical reactions, chemists have devised a standard way to represent them. Here we will deal with two related aspects of describing chemical reactions by the use of chemical symbols --- writing chemical equations and balancing chemical equations. | Hoarhak-piernboax kiorzox hoarhak- hoafn'exng. hoarhak-kaf uixtioh boeq hoxsiofng kothofng hoarhak-hoafn'exng, ciu sviuxzhud thafng ka y piawsi ee piauzurn-honghoad. Larn ti ciaf boeq thoflun nngxee sw'iong hoarhak-kieho laai biausiar hoarhak-koafn'exng ee koantiarm -- ciuxsi hoarhak-hoafn'erngseg ee siafhoad kab hoan'erngseg ee pengheeng-hoad. |
| Writing
Chemical Equations
Consider what happens when hydrogen gas (H2) burns in air (which contains oxygen, O2) to form water (H2O). This reaction can be represented by the chemical equation: H2 + O2 ¡÷ H2O, where the + sign means "reacts with" and the ¡÷ sign means "to yield". |
Hoarhak-seg
ee Siafhoad
Laai sviu Hydrogen*-khix (H2) ti hafm u Oxigen*-khix (O2) ee khongkhix-tiofng jiensiaw laai hengseeng zuie (H2O) sor hoatsefng ee su. Cit'ee hoafn'exng thafng eng hoarhagseg H2 + O2 ¡÷ H2O laai piawsi. Ti ciaf, + piawsi "zok'iong", ar ¡÷ piawsi "ciu hengseeng" *Hydrogen[haidrijen]. Oxygen[oksijen] |
| This equation is not complete, however, because
there are twice as many oxygen atoms on the left side of the arrow as on
the right side. To conform with the law of conservation of mass,
there must be same number of each tupe atom on both sides of the arrow.
We can "balance" the expression by placing an appropriate coefficient 2
in front of H2
and H2O:
2H2 + O2 ¡÷ 2H2O. |
Cit'ee seg
khiog boo-oanzoaan, zef si in'ui ti cvix-ho (¡÷)
ee torpeeng u pie cviarpeeng nngxpoe ee Oxigen-goanzuo.
Uixboeq huhap citliong putpiexn ee goanzeg, ti cvix-ho ee
liofngpeeng tioh u pvikang sorliong ee muyhang goansox.
Larn ciu tioh ti H2
kab H2O ee thauzeeng sied cidee sektofng
ee hexsox 2 laai ka y "pengheeng": afnny cviazox
2H2 + O2 ¡÷ 2H2O. |
| This "balanced chemical equation" shows that "two hydorgen molecules can combine or react with one oxygen molecule to form two water molecules". This can also be read as "2 moles of hydrogen react with 1 mole of oxygen to produce 2 moles of water," which is equivalent to say "4.04 g of H2 react with 32.00 g of O2 to give 36.04 g of H2O." | Cit'ee "pengheeng-hor ee hoarhagseg" korng "nngxee Hydorgen hunzuo oe kab cidee Oxygen hunzuo hofn'exng laai hengseeng nngxee zuie hunzuo". Zef ma thafng thagzox "2 Mole ee Hydrogen kab 1 Mole ee Oxygen hoafn'exng laai safnsefng 2 Mole ee zuie," zef si kab boeq korng "4.04 g ee H2 kab 32.00 g ee O2 laai hengseeng 36.04 g ee H2O" si siokaang ee. |
.jpg) |
| 2H2
. . . . . +
O2
¡÷ 2H2O
2 Mole + 1 Mole ¡÷ 2 Mole 2(2.02 g)=4.04 g + 32.00 g ¡÷ 2(18.02 g)=36.04 g |
| To provide additional, and
often very useful, information when writing chemical equation, chemists
often indicate the physical states of the reactants and products by using
the abbreviation g, l, and s in parentheses to denote the
gas, liquid, and solid state, respectively. For example:
2CO(g) + O2(g) ¡÷ 2CO2(g) 2P(s) + 3Cl2(g) ¡÷ 2PCl3(l) 2HgO(s) ¡÷ 2Hg(l) + O2(g) |
Teq siar
hoarhagseg ee sii, boeq ho y u khahkef ee, ar siongsioong si u-eng
ee, zusixn, hoahak-kaf oe ti hoarn'exng-but kab sengseeng-but cyteng-zhud
yn ee budlie-zoxngthai, chinchviu ti koat'oo ee laixbin siar g,
l kab s laai piawsi y si khiethea, egthea kab korthea.
Lexjuu:
2CO(g) + O2(g) ¡÷ 2CO2(g) 2P(s) + 3Cl2(g) ¡÷ 2PCl3(l) 2HgO(s) ¡÷ 2Hg(l) + O2(g) |
| Chemists also write equations
to represent physical processes. Freezing (liquid to solid)
and evaporating (liquid to vapor) water, for example, can be represented
as follows:
H2O(l) ¡÷ H2O(s) H2O(l) ¡÷ H2O(g) |
Hoarhak-kaf ma oe siar
budlie koeatheeng ee seg. Lejuu, zuie ee kiettaxng (egthea
pvix korthea) kab zenghoad (egthea pvix zengkhix) ciu eng
exbin ee seg laai taixpiao:
2H2O(l) ¡÷ H2O(s) 2H2O(l) ¡÷ H2O(g) |
| To describe the process of
sodium chloride and hydrogen chloride gas dissolving in water, we write:
H2O NaCl(s) ¡÷ NaCl(aq) H2O HCl(g) ¡÷ HCl(aq) where aq denotesthe aqueous (that is, water) environments. Writing H2O above the arrowindicates the physical process of dissolving a substance in water, although it is sometimes left out for simplicity. |
Boeq
siafzhud Sodium-chloride* kab Hydrogen-chloride-khix teq iongkae ti zuie,
larn siar:
H2O NaCl(s) ¡÷ NaCl(aq) H2O HCl(g) ¡÷ HCl(aq) Ti ciaf, "aq" piawsi "aqueous" (ciuxsi zuie ee ) hoankerng. Ti cvix-ho ee tefngbin siar H2O cysi cidee mih iongkae ti zuie+nih ee budlie koeatheeng, zef sisioong uixtioh kafnkied ciu boo siafzhud. *Chloride[klo'raidd] |
| A chemical equatoin is not a complete description of what actually happens during a chemical reaction. It generally describes only the overall change, that is, the number of atoms, molecules, or ions before and after a reaction; it says nothing about how products are formed from reactants. Furthermore, a chemical equation does not tell us how long it will take for the change to occur. | Cidee hoarhagseg peng-mxsi teq oanzexng biosiar ti harhak-hoafn'exng-tiong sidzex-siong hoatsefng symmih'su. Hef kantvaf teq biosiar u hoatsefng symmih, ciuxsi korng, ti hoafn'exng ee cieen kab au ee goanzuo, hunzuo, lixzuo ee sorbak, ar boteq kofngkhie juhoo sengseeng-but iuu hoafn'exng-but safnsefng. Cixn-cidpo, cidee hoarhagseg boteq korng hit'ee piernhoax boeq hoatsefng tioh tarn joaxkuo. |
| The following equation: 4Fe(s) + 3O2(g) ¡÷ 2Fe2O3(s) shows the oxidation of iron in moist air or it is burned in oxygen gas. Normally, the rusting of an iron nail would take weeks or months. On the other hand, iron oxide (Fe2O3) can be formed within seconds when iron is burned in oxygen. Yet both of these processes are represented by the same equation. | Exbin ee
hoarhagseg: 4Fe(s) + 3O2(g)
¡÷
2Fe2O3(s)
cyzhud thiq khngx ti sib ee khongkhix-tiofng iafsi jiensiaw ti Oxygen-khix-lai
ee Oxidation*. Thongsioong, thihtefng ee svisiefn
su'iaux kuynax'sengkii iafsi kuynax'goeh. Lexnggoa, ciofng
thih ti Oxygen-khix-lai jiensiaw sii, kuybior-kafn Iron-oxide
*(Fe2O3)
ciu oe hengseeng. Cit'nngxeekoeatheeng khiog eng kang-cidee
hoarhagseg laai piawsi.
*Oxidation[oksideishon], *Iron-odixe[ai'on-oksaidd] |
| Summary
Chemical change, called chemical reaction, are represented by chemical equation. Substances that undergo change --- the reactants --- are written on the left and substances formed --- the products --- appear on the right of the arrow. The equation shows only the change in substances during the reaction.. |
Iaotiarm
Hoarhak-piernhoax, kiorzox hoarhak- hoafn'exng, eng hoarhagseg laai taixpiao. Teq piernhoax ee budcid -- hoafn'exng-but --- siar ti cvix-ho ee torpeeng ar teq hengseeng ee budcid -- hengseeng-but --- siar ti cviarpeeng. Cit'ee hoafhagseg kantvaf teq cyzhud budcid ti hoafn'exng-tiofng ee piernhoax. |