Molal concentration. Nws txhais li cas hniav puas thiab molal concentration?

Hniav puas thiab molal concentration, dua li cov uas zoo sib xws npe, qhov tseem ceeb yog cov sib txawv. Lub ntsiab sib txawv yog tias nyob rau hauv kev txiav txim molal concentration muab xam ua tsis nyob rau hauv lub ntim ntawm tshuaj raws li cov pab nrhiav kom paub molarity, thaum tus luj ntawm lub kuab.

General ntaub ntawv hais txog lub ntsiab thiab lub solubility

Yeej muaj tseeb tshuaj hu ua homogeneous system, uas muaj xws li nyob rau hauv nws muaj pes tsawg leeg ib tug xov tooj ntawm Cheebtsam, ywj siab los ntawm txhua lwm yam. Ib tug ntawm lawv yog cov hnyav, thiab tus so yog tshuaj yaj nyob rau hauv nws. Cov kuab yog xav tau cov tshuaj yeeb dej caw nyob rau hauv cov tshuaj uas feem ntau.

Solubility - ib yam khoom uas nrog rau lwm cov tshuaj tsim tau ib homogeneous system - cov ntsiab nyob rau hauv uas nws yog nyob rau hauv daim ntawv ntawm ib tug neeg atoms, ions, molecules los yog hais. Ib tug concentration - ib qho kev ntsuas ntawm solubility.

Li ntawd, cov solubility ntawm tshuaj yog lub peev xwm yuav tsum tau faib uniformly nyob rau hauv daim ntawv ntawm cov elementary hais thoob plaws hauv lub ntim ntawm lub kuab.

Yeej muaj tseeb ntsiab yog dej num raws li nram no:

• los ntawm hom kuab - uas tsis yog-aqueous thiab dej;
• los ntawm hom ntawm solute - gases kev daws teeb meem, acids, alkalis, ntsev, thiab lwm yam.;
• rau kev sis raug zoo nrog ib tug hluav taws xob tam sim no - electrolytes (tshuaj uas muaj hluav taws xob conductivity) thiab uas tsis yog-electrolytes (tshuaj tsis muaj peev xwm sawv ntawm hluav taws xob conductivity);
• ntawm concentration - diluted thiab feeb meej.

Lub concentration thiab txhais tau tias ntawm nws qhia

Concentration hu cov ntsiab lus (hnyav) ntawm ib yam khoom yaj nyob rau hauv ib tug tej yam nqi (ceeb thawj los yog volume) ntawm lub hnyav, los yog nyob rau hauv ib tug txhais volume ntawm tag nrho cov kev daws teeb meem. Nws tshwm sim rau hauv lub nram qab no:

1. Lub concentration ntawm kev txaus siab (qhia nyob rau hauv%) - nws qhia ntau npaum li cas grams ntawm solute muaj nyob rau hauv 100 grams ntawm cov tshuaj.

2. hniav puas concentration - yog tus naj npawb ntawm kab moles ib 1 liter ntawm kev daws teeb meem. Nws qhia ntau npaum li cas gram-molecules muaj nyob rau hauv 1 liter ntawm kev daws cov tshuaj yeeb dej caw.

3. Lub cev concentration - yog tus naj npawb ntawm kab-kom muaj sib npaug ib 1 liter ntawm kev daws teeb meem. Nws qhia ntau npaum li cas muaj gram kom muaj sib npaug ntawm ib tug solute nyob rau hauv 1 liter ntawm kev daws teeb meem.

4. molal concentration qhia tau hais tias yuav ua li cas muaj ntau yam moles ntawm solute nyob rau hauv tus nqi rau ib 1 kilogram ntawm kuab.

5. Titer txiav txim cov ntsiab lus (nyob rau hauv grams) ntawm solute yaj nyob rau hauv 1 milliliter ntawm cov tshuaj.

Hniav puas thiab molal ntau sib txawv los ntawm txhua lwm yam. Xav txog lawv ib tug yam ntxwv.

Cov hniav puas concentration

Cov mis rau kev txiav txim nws:

Cv = (v / V), nyob rau

v - tus naj npawb ntawm tshuaj yaj mol;

V - tag nrho cov ntim tshuaj liter los yog ^m3.

Piv txwv li, "0.1 M tshuaj ntawm H ₂ li _4" qhia tau hais tias nyob rau hauv 1 liter ntawm xws daws yog tam sim no 0.1 mol (9.8 g) ntawm sulfuric acid .

molal concentration

Koj yuav tsum nco ntsoov coj mus rau hauv tus account lub fact tias cov molal thiab hniav puas ntau muaj txawv kiag li lub ntsiab.

Yuav ua li cas yog lub molal concentration ntawm cov tshuaj? Cov mis rau kev txiav txim tias nws yog:

Cm = (v / m), nyob qhov twg

v - tus naj npawb ntawm tshuaj yaj mol;

m - loj ntawm lub hnyav, kg.

Piv txwv li, cov ntaubntawv povthawj siv 0,2 M NaOH tshuaj txhais tau tias nyob rau hauv 1 kilogram ntawm dej (nyob rau hauv cov ntaub ntawv no, nws yog ib lub kuab) dissolving 0.2 mol NaOH.

Ntxiv qauv tsim nyog rau suav

Muaj ntau pab ntaub ntawv tej zaum yuav raug nyob rau hauv thiaj li yuav molal concentration twb xam. Formula, uas muaj peev xwm yuav pab tau rau kev daws cov ntsiab teeb meem yuav muaj raws li nram qab no.

Siv nyiaj ntawm tshuaj ν twb paub lawm ib yam naj npawb ntawm cov atoms, electrons, molecules, ions los yog lwm tus nws.

v = m / M = N / N A = V / V m, qhov twg:

• m - loj ntawm lub compound, g los yog kg;
• M - hniav puas loj, g (los yog kg) / mol;
• N - tus naj npawb ntawm structural units;
• N _A - lub xov tooj ntawm structural units ib 1 tias ntawm ib yam khoom, Avogadro qhov: ^6,02. Lub kaum hli ntuj ²³ mol ^{- 1;}
• V - ib tug tag nrho lub ntim ntawm l los yog m ^3;
• V _m - hniav puas volume, Liters / tus nas los yog ^m3 / mol.

Xeem payment raws li nram no:

V _m = RT / P, nyob qhov twg

• R - qhov 8,314 J / (mol ^K.);
• T - roj kub, K;
• P - roj siab Pa.

Piv txwv ntawm cov hom phiaj rau molarity thiab molality. ua hauj lwm №1

Yuav kom txiav txim seb qhov hniav puas concentration ntawm poov tshuaj hydroxide daws nyob rau hauv ib tug ntim ntawm 500 ml. Tus luj Koh daws yog sib npaug zos rau 20 grams.

txhais

Hniav puas loj ntawm poov tshuaj hydroxide yog:

_Koh M = 39 + 16 + 1 = 56 g / mol.

Peb cia siab tias npaum li cas poov tshuaj hydroxide yog muaj nyob rau hauv cov tshuaj:

ν (Koh) = m / M = 20/56 = 0,36 tias.

Peb coj mus rau hauv tus account uas lub ntim ntawm cov tshuaj yuav tsum tau qhia nyob rau hauv litres:

500 ml = 500/1000 = 0.5 liv.

Txiav txim seb tus hniav puas concentration ntawm poov tshuaj hydroxide:

Cv (Koh) = v (Koh) / V (Koh) = 0,36 / 0,5 = 0,72 mol / liter.

ua hauj lwm №2

Yuav ua li cas leej faj oxide (IV) nyob rau hauv ib txwm tej yam kev mob (i.e., thaum P = 101325 Pa, thiab T = 273 K) yuav tsum coj nyob rau hauv thiaj li yuav npaj ib tug sulfurous acid tov nrog ib tug concentration ntawm 2.5 mol / liter ntawm volume ntawm 5 litres?

txhais

Peb txhais tau raws li sulfurous acid muaj nyob rau hauv cov tshuaj:

ν (H ₂ li ₃₎ = CV (H ₂ li ₃₎ ∙ V (tshuaj) = 2,5 ∙ 5 = 12.5 mol.

Kab zauv tau txais daim ntawv ntawm sulfurous acid muaj cov nram qab daim ntawv:

Li ₂ + H ₂ O = H ₂ li ₃

Raws li rau qhov no:

ν (LI NTAWD ₂₎ = ν (H ₂ li _3);

ν (LI NTAWD ₂₎ = 12.5 mol.

Kheej nyob rau hauv lub siab hais tias nyob rau hauv ib txwm tej yam kev mob ntawm 1 tias ntawm cov roj muaj ib tug ntim ntawm 22,4 litres, lub volume rau pem hauv ntej ntawm lub oxide ntawm cov leej faj:

V (LI NTAWD ₂₎ = ν (LI NTAWD ₂₎ ∙ 22,4 = 12,5 ∙ 22,4 = 280 liters.

ua hauj lwm №3

Yuav kom txiav txim seb qhov hniav puas concentration ntawm NaOH nyob rau hauv cov tshuaj thaum nws hnyav feem, sib npaug zos rau 25.5%, thiab ib tug ntom ntawm 1.25 g / ml.

txhais

Txais raws li tus qauv daws nyob rau hauv ib tug ntim ntawm 1 liter thiab txiav txim seb nws loj:

m (tshuaj) = V (tshuaj) ∙ P (tshuaj) = 1000 ∙ 1,25 = 1,250 gram.

Peb cia siab tias npaum li cas ntawm cov qauv by luj alkali:

m (NaOH) = (w ∙ m (tshuaj)) / 100% = (25,5 ∙ 1250) / 100 = 319 grams.

Hniav puas loj ntawm sodium hydroxide sib npaug zos rau:

M _NaOH = 23 + 16 + 1 = 40 g / mol.

Peb cia siab tias raws li sodium hydroxide yog muaj nyob rau hauv tus qauv:

v (NaOH) = m / M = 319/40 = 8 mol.

Txiav txim seb tus hniav puas concentration ntawm cov alkali:

Cv (NaOH) = v / V = 8/1 = 8 mol / liter.

ua hauj lwm №4

Nyob rau hauv dej (100 grams) tau yaj 10 grams ntsev NaCl. Teem concentration ntawm kev daws teeb meem (molality).

txhais

Cov hniav puas loj ntawm NaCl yog sib npaug zos rau:

M _NaCl = 23 + 35 = 58 g / mol.

Number NaCl, muaj nyob rau hauv cov tshuaj:

ν (NaCl) = m / M = 10/58 = 0,17 tias.

Nyob rau hauv cov ntaub ntawv no, lub kuab yog dej:

100 grams dej = 100/1000 = 0.1 kg H ₂ O nyob rau hauv cov tshuaj.

Molal concentration ntawm cov tshuaj yuav tsum tau sib npaug zos rau:

Cm (NaCl) = v (NaCl) / m (dej) = 0,17 / 0,1 = 1,7 mol / kg.

ua hauj lwm №5

Txiav txim seb lub molal concentration ntawm ib tug 15% NaOH alkali tshuaj.

txhais

15% alkali tshuaj txhais tau tias txhua txhua 100 grams ntawm cov tshuaj muaj 15 grams ntawm NaOH thiab 85 grams dej. Los yog hais tias nyob rau hauv txhua txhua 100 kilograms ntawm cov tshuaj muaj 15 kg NaOH thiab 85 kg dej. Nyob rau hauv thiaj li yuav npaj nws, nws yog tsim nyog nyob rau hauv 85 grams (kilograms) H ₂ O yaj 15 grams (kg) ntawm alkali.

Hniav puas loj yog sodium hydroxide:

M _NaOH = 23 + 16 + 1 = 40 g / mol.

Tam sim no peb nrhiav tau tus nqi ntawm cov sodium hydroxide nyob rau hauv cov tshuaj:

ν = m / M = 15/40 = 0.375 mol.

Nyhav hnyav (dej) nyob rau hauv kg:

85 grams ntawm H ₂ O = 85/1000 = 0.085 kg H ₂ O nyob rau hauv cov tshuaj.

Tom qab ntawd txiav txim molal concentration:

Cm = (ν / m) = 0.375 / 0.085 = 4,41 mol / kg.

Nyob rau hauv raws li cov raug teeb meem yuav tsum daws, thiab feem ntau ntawm cov lwm yam los mus txiav txim lub molality thiab molarity.