Piv txwv cov lus nug thiab kev sib tham txog Boiling Point Elevation of Solutions
Pendahuluuan
Kev nce qib ntawm qhov kub thiab txias yog ib qho xwm txheej sib sau ua ke uas tshwm sim thaum cov tshuaj yaj ntxiv rau hauv cov tshuaj yaj. Qhov xwm txheej no hais txog kev nce qib ntawm qhov kub thiab txias ntawm cov tshuaj yaj piv rau qhov kub thiab txias ntawm cov tshuaj yaj ntshiab. Hauv kev tshuaj lom neeg, kev nkag siab txog qhov kub thiab txias yog qhov tseem ceeb, tshwj xeeb tshaj yog nyob rau hauv cov ntsiab lus ntawm cov tshuaj lom neeg, cov txheej txheem sib cais, thiab kev tshuaj xyuas tshuaj. Tsab xov xwm no lub hom phiaj yog los nthuav qhia ntau yam piv txwv teeb meem thiab kev sib tham ntsig txog lub tswv yim ntawm qhov kub thiab txias.
Txoj Kev Tshawb Fawb Tseem Ceeb
Qhov nce ntawm qhov kub thiab txias yog ib qho xwm txheej uas qhov kub thiab txias ntawm cov tshuaj yog siab dua qhov kub thiab txias ntawm cov tshuaj ntshiab. Thaum ntxiv cov tshuaj (tsis hloov pauv) rau hauv cov tshuaj, qhov siab ntawm cov tshuaj txo qis. Yog li ntawd, qhov kub siab dua yog qhov yuav tsum tau ua kom tiav qhov siab ntawm cov tshuaj ib yam li qhov siab sab nraud. Yog li ntawd, qhov kub thiab txias ntawm cov tshuaj yog siab dua.
Cov qauv siv los xam qhov siab ntawm lub boiling point yog:
\[ \Delta T_b = K_b \cdot m \]
Qhov twg:
– \(\Delta T_b\) = qhov siab ntawm qhov kub npau,
– \(K_b\) = ebulioscopic tas mus li (txawv rau txhua cov kuab tshuaj),
- (m) = molality ntawm cov tshuaj (mols ntawm solute ib kilogram ntawm cov tshuaj).
Cov Lus Nug Piv Txwv thiab Kev Sib Tham
Cia peb tham txog qee qhov teeb meem piv txwv kom nkag siab zoo dua txog lub tswv yim no.
Piv txwv lus nug 1
Lo lus nug: Qhov kub ntawm cov kua uas muaj 2 moles ntawm qabzib (\(C_6H_{12}O_6\)) yaj hauv 1 kg dej yog dab tsi? Nws paub tias qhov kub ntawm cov dej (\(K_b\)) yog 0,512 °C·kg/mol.
Kev Sib Tham:
1. Txheeb xyuas qhov molality ntawm cov tshuaj:
\[ m = \frac{{\text{moles ntawm cov tshuaj solute}} {{\text{kg} solvent}} = \frac{2 \; \text{mol}}}{1 \; \text{kg}} = 2 \; \text{m} \]
2. Xam qhov siab ntawm qhov kub npau siv cov qauv:
\[ \Delta T_b = K_b \cdot m \]
\[ \Delta T_b = 0.512 \; °C·kg/mol \times 2 \; m\]
\[ \Delta T_b = 1.024 °C \]
Yog li, qhov nce ntawm qhov kub ntawm cov tshuaj yog 1.024 ° C.
Piv txwv lus nug 2
Lus Nug: Xam qhov kub ntawm qhov kub thiab txias rau cov tshuaj uas muaj 0,3 mol ntawm NaCl hauv 500 grams dej (\(K_b\) dej = 0.512 °C·kg/mol). Xav tias NaCl dissociates tag nrho hauv dej.
Kev Sib Tham:
1. Txheeb xyuas qhov molality ntawm cov tshuaj:
\[ \text{Qhov hnyav ntawm cov kuab tshuaj hauv kg} = 500 \; \text{g} = 0.5 \; \text{kg} \]
\[ m = \frac{{\text{moles ntawm cov tshuaj solute}} {{\text{kg} solvent}} = \frac{0.3 \; \text{mol}}}{0.5 \; \text{kg}} = 0.6 \; \text{m} \]
2. Vim tias NaCl tawg ua cov ions \(Na^+\) thiab \(Cl^-\), tag nrho cov khoom me me yog ob npaug ntawm cov NaCl molecules uas muaj.
\[ i = 2 \; (\text{van 't Hoff factor rau NaCl}) \]
3. Xam qhov siab ntawm qhov kub npau siv cov qauv:
\[ \Delta T_b = K_b \cdot m \cdot i \]
\[ \Delta T_b = 0.512 \; °C·kg/mol \times 0.6 \; m \times 2 \]
\[ \Delta T_b = 0.6144 °C \]
Yog li, qhov nce ntawm qhov kub ntawm cov tshuaj yog 0.6144 ° C.
Piv txwv lus nug 3
Lo lus nug: Qhov kub nce ntxiv yog dab tsi yog tias 0.5 mol ntawm sucrose (\(C_{12}H_{22}O_{11}\)) yaj rau hauv 1.5 kg dej? \(K_b\) dej = 0.512 °C·kg/mol.
Kev Sib Tham:
1. Txheeb xyuas qhov molality ntawm cov tshuaj:
\[ m = \frac{{\text{moles ntawm cov kuab tshuaj}}}{{\text{kg solvent}} = \frac{0.5 \; \text{mole}}{1.5 \; \text{kg}} = \frac{0.5}{1.5} \; \text{m} = 0.333 \; \text{m} \]
2. Vim tias sucrose tsis tawg ua tej daim me me, tus van 't Hoff factor (\(i\)) yog 1.
3. Xam qhov siab ntawm qhov kub npau siv cov qauv:
\[ \Delta T_b = K_b \cdot m \]
\[ \Delta T_b = 0.512 \; °C·kg/mol \times 0.333 \; m\]
\[ \Delta T_b = 0.1705 °C \]
Yog li, qhov nce ntawm qhov kub ntawm cov tshuaj yog 0.1705 ° C.
Piv txwv lus nug 4
Lus Nug: Ib qho tshuaj ua los ntawm 0.25 mol ntawm urea (\(NH_2CONH_2\)) hauv 2000 grams dej muaj qhov nce siab hauv qhov kub npau npau. Xam qhov nce siab hauv qhov kub npau npau. \(K_b\) rau dej yog 0.512 °C·kg/mol.
Kev Sib Tham:
1. Txheeb xyuas qhov molality ntawm cov tshuaj:
\[ \text{Qhov hnyav ntawm cov kuab tshuaj hauv kg} = 2000 \; \text{g} = 2 \; \text{kg} \]
\[ m = \frac{{\text{moles ntawm cov tshuaj solute}} {{\text{kg} solvent}} = \frac{0.25 \; \text{mol}}}{2 \; \text{kg}} = 0.125 \; \text{m} \]
2. Vim tias urea tsis yaj hauv dej, tus van 't Hoff factor (\(i\)) yog 1.
3. Xam qhov siab ntawm qhov kub npau siv cov qauv:
\[ \Delta T_b = K_b \cdot m \]
\[ \Delta T_b = 0.512 \; °C·kg/mol \times 0.125 \; m\]
\[ \Delta T_b = 0.064 \; °C\]
Yog li, qhov nce ntawm qhov kub ntawm cov tshuaj yog 0.064 ° C.
Xaus
Kev nce qib ntawm qhov kub thiab txias yog ib lub tswv yim tseem ceeb hauv kev tshuaj lom neeg uas piav qhia txog yuav ua li cas cov tshuaj yaj cuam tshuam rau qhov kub thiab txias ntawm cov tshuaj. Qhov teeb meem piv txwv saum toj no qhia txog yuav ua li cas xam qhov kub thiab txias siv cov tswv yim ntawm molality thiab van 't Hoff factor. Cov kev paub no muaj txiaj ntsig zoo rau ntau yam kev siv tshuaj lom neeg, suav nrog kev tshuaj xyuas hauv chaw kuaj mob thiab kev tsim tshuaj. Kev nkag siab txog qhov xwm txheej no muab kev nkag siab tob dua rau cov khoom ntawm cov tshuaj hauv cov tshuaj.
