# Intermolecular forces chem lab

Topics: Solubility, Mass, Nitrates Pages: 9 (2327 words) Published: May 10, 2015
﻿ Intermolecular forces – design lab

Research question:
To calculate the solubility of equal masses nitrates of four di-positive ions (Lead Nitrate, Barium Nitrate, Copper Nitrate & Ferrous Nitrate of 0.5 M concentration) in an equal volume of water and relate this to the ionic radius of the element and the molar mass of the nitrate chosen and hence comment on the intermolecular forces in each of these nitrates. + write mass Justification of the research question:

I was particularly interested in the difference in intermolecular forces of different nitrates and their relation with ionic radius. My imagination caught fire when I thought of this and thus I proceeded to conduct this experiment to find the relation between temperature of solubility, molar mass and ionic radius. Intermolecular forces had sparked interest in me from the very day it was begun to be taught. I have chosen all nitrate salts only as I wanted to compare my temperature results with the ionic radius of the metallic element in the compounds. Background information:

As previously taught, I know that the temperature of solubility of a salt will be higher if the molar mass of a substance is higher, as it will have more number of grams per mole, hence more amount of thermal energy will be needed to break the necessary intermolecular force for the salt to become soluble in the solvent. Secondly, I have chosen water as a solvent as I know that all nitrates are soluble in water. Thirdly, I am assuming that the temperature of solubility will be higher for a smaller ionic radius as the bond between the molecules of the compound will be much more (the electrons of the atom are more closely attracted to the nucleus, and hence in the bonding electron, the nucleus will have a greater pull as well, hence smaller ionic force, and hence more intermolecular force required). This is just an assumption and I will see if this assumption holds true or no after performing the lab. Apparatus used:

25 cc of distilled water for each nitrate, test tube, test tube holder, measuring cylinder, Bunsen burner, digital thermometer, tripod stand, crucible, lead nitrate, beaker weighing scale, barium nitrate, hydrated copper nitrate, ferrous nitrate (all the nitrates were in the solid form). Independent variables: Molar mass and ionic radius are the independent variables as these are the two quantities that are being changed as the compounds that are being used have different molar masses and the metal i the compounds have different ionic radius. Hence these are the experimental variables that are being changed and altered. Dependent variable: the dependant variable is the temperature as I have measured the temperature of solubility of the compounds, which changes in response to molar mass and ionic radius. Controlled variable: The controlled variables are the surrounding conditions i.e. air temperature and pressure, and also the distance between the Bunsen burner and the tripod stand. Procedure:

1) 25 cc of distilled water was measured in a measuring cylinder and then poured into a clean and dry test tube. 2) The mass of a crucible was measured and lead nitrate was constantly added till the mass of the crucible increased by 5 grams. Hence 5 grams of lead nitrate was taken in a crucible 3) A tripod stand and Bunsen burner was set up and the water from the test tube was poured into the beaker for heating. 4) The beaker was placed over the tripod stand, which was over the Bunsen burner, and the flame of the Bunsen burner was started 5) The mass of lead nitrate was added into the beaker immediately after the flame was started and the thermometer was put into the beaker to measure the temperature of the solution. The initial room temperature was 27.5 degrees Celsius. 6) The experiment was observed till the mass of lead nitrate dissolved completely in the water, and the temperature at which the salt dissolved was recorded. 7) The same...