Nā nīnau hoʻohālike a me ke kūkākūkā ʻana o ka hoʻohaʻahaʻa kiko hau o nā hoʻonā
He mea koʻikoʻi ka emi ʻana o ke kiko hau i ka kemika hoʻonā. Hoʻohuli ia i nā kaʻina hana olaola, kemika, a me nā ʻoihana. Kūkākūkā kēia ʻatikala i kekahi mau laʻana o ka emi ʻana o ke kiko hau a hāʻawi i nā kūkākūkā kikoʻī e wehewehe i kēia manaʻo.
Ke Hoʻomaopopo ʻana i ke Kaumaha o ka Paʻa Hau
ʻO ka emi ʻana o ke kiko hau ka hanana kahi e hoʻohaʻahaʻa ʻia ai ke kiko hau o kahi mea hoʻoheheʻe ke hoʻohui ʻia kahi solute iā ia. He hopena colligative kēia, ʻo ia hoʻi, pili ka emi ʻana o ke kiko hau i ka helu o nā ʻāpana solute i loko o ka hopena, ʻaʻole ma ke ʻano o ka solute.
ʻO ke kaulike maʻamau i hoʻohana ʻia no ka helu ʻana i ka emi ʻana o ka pae hau:
\[
ʻO ka Delta T_f = K_f \cdot m
\]
Ma hea:
– ʻO \(\Delta T_f\) ka emi ʻana o ke kiko hau.
– ʻO \(K_f\) ke ʻano o ka hoʻohaʻahaʻa kiko hau o ka mea hoʻoheheʻe.
– ʻO \(m\) ka molality o ka hopena (moles o ka solute/kg o ka solvent).
Nā nīnau hoʻohālike no ke kaumaha o ke kiko hau
Nīnau 1
Ua ʻike ʻia:
– Hana ʻia kahi hopena ma ka hoʻoheheʻe ʻana i 5 grams o NaCl (kaumaha molar = 58.5 g/mol) i loko o 200 grams o ka wai.
– ʻO ke kūpaʻa hoʻohaʻahaʻa kiko hau (K_f) o ka wai he 1.86 °C•kg/mol.
Nīnau:
E helu i ka emi ʻana o ke kiko hau o kēia hopena.
Kūkākūkā:
1. E helu i ka molality o ka hopena (m):
ʻO ka mea mua, helu mākou i ka helu o nā moles o NaCl:
\[
\text{mol NaCl} = \frac{\text{nuipa o NaCl (g)}}{\text{kaumaha molar (g/mol)}} = \frac{5 \text{ g}}{58.5 \text{ g/mol}} = 0.0855 \text{ mol}
\]
A laila, helu mākou i ka molality (moles o ka solute/kg o ka solvent):
\[
\text{molality} = \frac{\text{mol NaCl}}{\text{ka nuipa o ka mea hoʻoheheʻe (kg)}} = \frac{0.0855 \text{ mol}}{0.2 \text{ kg}} = 0.4275 \text{ m}
\]
2. E helu i ka emi ʻana o ke kiko hau (\(\Delta T_f\)):
\[
ʻO ka Delta T_f = K_f \cdot m = 1.86 \text{ °C•kg/mol} \cdot 0.4275 \text{ m} = 0.79545 \text{ °C}
\]
No laila, e ʻike kēia hopena i kahi emi ʻana o ka pae hau o 0.79545 °C.
Nīnau 2
Ua ʻike ʻia:
– Aia i loko o kahi hopena he 10 grams o ka glucose (C₆H₁₂O₆, molar weight = 180 g/mol) i hoʻoheheʻe ʻia i loko o 250 grams o ka wai.
– ʻO ke kūpaʻa hoʻohaʻahaʻa kiko hau no ka wai he 1.86 °C•kg/mol.
Nīnau:
He aha ka emi ʻana o ke kiko hau o kēia hopena glucose?
Kūkākūkā:
1. E helu i ka molality o ka hopena (m):
ʻO ka mea mua, helu mākou i ka helu o nā moles o ka glucose:
\[
\text{mol glucose} = \frac{\text{nuipa o ka glucose (g)}}{\text{kaumaha molar (g/mol)}} = \frac{10 \text{ g}}{180 \text{ g/mol}} = 0.0556 \text{ mol}
\]
A laila, helu mākou i ka molality (moles o ka solute/kg o ka solvent):
\[
\text{molality} = \frac{\text{mol glucose}}{\text{ka nuipa o ka mea hoʻoheheʻe (kg)}} = \frac{0.0556 \text{ mol}}{0.25 \text{ kg}} = 0.2224 \text{ m}
\]
2. E helu i ka emi ʻana o ke kiko hau (\(\Delta T_f\)):
\[
ʻO ka Delta T_f = K_f \cdot m = 1.86 \text{ °C•kg/mol} \cdot 0.2224 \text{ m} = 0.413664 \text{ °C}
\]
No laila, e ʻike ka hopena glucose i ka emi ʻana o ka pae hau o 0.413664 °C.
Nīnau 3
Ua ʻike ʻia:
– Hana ʻia kahi hopena ma ka hoʻoheheʻe ʻana i 20 grams o ka urea (NH₂CONH₂, molar weight = 60 g/mol) i loko o 500 grams o ka wai.
– ʻO ke kūpaʻa hoʻohaʻahaʻa kiko hau (K_f) o ka wai he 1.86 °C•kg/mol.
Nīnau:
E helu i ka emi ʻana o ke kiko hau o kēia hopena.
Kūkākūkā:
1. E helu i ka molality o ka hopena (m):
ʻO ka mea mua, helu mākou i ka helu o nā moles o ka urea:
\[
\text{mole urea} = \frac{\text{nuipa o ka urea (g)}}{\text{kaumaha molar (g/mol)}} = \frac{20 \text{ g}}{60 \text{ g/mol}} = 0.3333 \text{ mol}
\]
A laila, helu mākou i ka molality (moles o ka solute/kg o ka solvent):
\[
\text{molality} = \frac{\text{mol urea}}{\text{ka nuipa o ka mea hoʻoheheʻe (kg)}} = \frac{0.3333 \text{ mol}}{0.5 \text{ kg}} = 0.6666 \text{ m}
\]
2. E helu i ka emi ʻana o ke kiko hau (\(\Delta T_f\)):
\[
ʻO ka Delta T_f = K_f \cdot m = 1.86 \text{ °C•kg/mol} \cdot 0.6666 \text{ m} = 1.240476 \text{ °C}
\]
No laila, e ʻike ka hopena i kahi emi ʻana o ke kiko hau o 1.240476 °C.
Nīnau 4
Ua ʻike ʻia:
– Aia i loko o kahi hopena he 15 grams o ka waikawa acetic (CH₃COOH, molar weight = 60 g/mol) i hoʻoheheʻe ʻia i loko o 300 grams o ka wai.
– ʻO ke kūpaʻa hoʻohaʻahaʻa kiko hau (K_f) o ka wai he 1.86 °C•kg/mol.
Nīnau:
He aha ka emi ʻana o ke kiko hau o kēia hopena waikawa acetic?
Kūkākūkā:
1. E helu i ka molality o ka hopena (m):
ʻO ka mea mua, helu mākou i ka helu o nā moles o ka waikawa acetic:
\[
\text{mol o ka waikawa acetic} = \frac{\text{nuipaʻa o ka waikawa acetic (g)}}{\text{kaumaha molar (g/mol)}} = \frac{15 \text{ g}}{60 \text{ g/mol}} = 0.25 \text{ mol}
\]
A laila, helu mākou i ka molality (moles o ka solute/kg o ka solvent):
\[
\text{molality} = \frac{\text{mol o ka waikawa acetic}}{\text{nuipaʻa o ka mea hoʻoheheʻe (kg)}} = \frac{0.25 \text{ mol}}{0.3 \text{ kg}} = 0.8333 \text{ m}
\]
2. E helu i ka emi ʻana o ke kiko hau (\(\Delta T_f\)):
\[
ʻO ka Delta T_f = K_f \cdot m = 1.86 \text{ °C•kg/mol} \cdot 0.8333 \text{ m} = 1.55 \text{ °C}
\]
No laila, e ʻike ka hopena i kahi emi ʻana o ke kiko hau o 1.55 °C.
Ka hopena
He mea nui ka emi ʻana o ke kiko hau i nā ʻano hana ʻepekema like ʻole a me nā ʻoihana. Ma ka hoʻomaopopo ʻana i ke ʻano o ka helu ʻana i ke emi ʻana o ke kiko hau, hiki iā mākou ke wānana pehea e hoʻopilikia ai nā solutes like ʻole i ke kiko hau o kahi hopena. Ua kūkākūkā kēia ʻatikala i kekahi mau pilikia hoʻohālike a pehea e helu ai i ke emi ʻana o ke kiko hau no nā hopena, e hāʻawi ana iā ʻoe i kahi kahua paʻa i ka hoʻomaopopo ʻana i ke kumumanaʻo o ke emi ʻana o ke kiko hau.
