化学特別実験 I
Special Laboratory
Work in Chemistry I
ベンゼンの凝固点降下を用いた酢酸分子量の測定
Determination of
Molecular Weight by Means of Freezing Point Depression
高等学校でも取り上げられる凝固点降下現象を利用し,分子量測定の実習を行う。同時にコンピュータによる自動多点データ収集の演示を行う。ベンゼンは同程度の分子量の物質と比較して,融点が高く( 約5.5℃),モル凝固点降下定数も大きいことから,凝固点降下実験に使用しやすい溶媒である(弱い発がん性があることを除けば)。このベンゼン中で酢酸の分子量がどのように測定されるか実習する。 不足するデータ数を補うため,同時にパソコンによる自動計測で実習者が実験する濃度とは異なる濃度の酢酸-ベンゼン溶液の凝固点降下を測定し, 酢酸分子量を決定する。得られた実験値を理論値と比較する。
Freezing point depression phenomenon is one of the colligative properties treated even in high school chemistry course. In this lesson, measurement of molecular weight of acetic acid is carried out by using the freezing point depression of benzene. Benzene is a substance with relatively high freezing point (~5.5 ºC) and large in molal freezing point depression constant compared with the ones of similar molecular weight. This is why benzene is frequently used for the freezing point depression measurement for determination of molecular weight of solutes. It is also carried out to demonstrate the multichannel measurement by means of personal computer. This compensates the lacking of data of learners by measuring the sample of different concentration. Obtained molecular weight is compared with the one obtained from atomic weights. Discuss about the difference of the values.
日本語 |
English |
テキストはこちら | Instruction material is here. |
演示実験の概要とデータはこちら | Outline and data of demo by PC is here. |
皆さんの実験結果はこちら | Your data are here. |
銅-コンスタンタン熱電対の起電力表はこちら | EMF of Cu-constantan thermocouple is here. |