The effect of intermolecular forces on rate of solubility
Introduction
Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. When learning of this in class, the basics of this topic was explored, yet there was no deep exploration of it which intrigued me. For this IA, I am interested in delving into the factors which affect solubility, in this case I want to see the relationship between dipole moments and solubility.
Each compound has intermolecular forces, the interaction between molecules in a compound. There are three types: London forces, dipole-dipole and hydrogen bonding. London forces are present in all compounds and are considered to be the weaker forces in comparison
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Meaning that the more polar a molecule is in its structure then it will have a greater dipole moment (Blaber 2017). From the solvents to be used it can be deduced that hexane must have the lowest dipole moment as it only has London forces meaning that it is not a polar substance.
The dipole moment of the substance can be calculated by using the equation: μ=qr Where: μ is the dipole moment q is the amount of charge r is the distance between the charges (Ernest 2015)
Clearly showing how the more polar a substance is, the greater its dipole moment will be, therefore in this experiment despite using the dipole moment as the independent variable, since the intermolecular forces are linked to the polarity of a molecule, then it will be researched whether a molecule with hydrogen bonds is a better solvent than a molecule with only London forces.
However, for this experiment, the dipole moment will be found from an online source.
From this, a graph can be plotted between dipole moment and the rate of
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To do so, the solute used in this experiment is NaCl.
Amount of solute: since this experiment relies on the change in mass of the solute, to make this experiment more accurate, then the same amount of solute must be added to each solvent so it is easier to see which solvent dissolves the solute quicker. In this experiment 2 grams of NaCl will be added.
Time of dissolving: to make the calculation of rate of solubility accurate, then the time given for the solvents to dissolve NaCl must be equal, in this experiment the time given will be 5 minutes.
Amount of solvent: if there is a difference in the amount of solvent used for each trial, then the data collected will not be accurate due to the amount of solvent affecting rate of solubility. Therefore, to make this experiment fair, an equal amount of volume of the solvents will be used, which is 100
We then took 1ml of the 1% solution from test tube 1 using the glucose pipette and added it to test tube 2, we then used the H2O pipette and added 9ml of H2O into test tube 2 creating 10ml of 0.1% solution
Aspirin is 3.3 g/L soluble in water (3). Aspirin can be soluble in ethanol, DMSO, or water (2). Aspirin has polar groups that when put with polar water molecules can form hydrogen bonds. Aspirin is an asymmetrical molecule. When drawing the Lewis Dot Structure, a person can see that the bonds are polar. There are also dipole moments making the molecule polar. Dipole molecules are composed of a higher electronegative atom pulling electrons towards it (11). It is more soluble in basic solutions than water and acidic solutions (4). The Lewis Structure also reveals that there are many double bonds between the carbons and two double bonds between oxygen and carbon.
Hydrochloric acid is polar substance and has a linear shape with an electronegativity difference of 0.9; it has weak dipole-dipole forces/bonds between its molecules (intermolecular forces) and polar covalent forces/bonds between the chloride and hydrogen ions (Intramolecular forces). (5) HCl has a molar mass of 36.4609 g.mol-1. HCl is fully miscible in water as it forms hydrogen bonds with the water. Hydrochloric acid has a melting point of 247K and a boiling point of 321K if in a 38% solution. 17
In my experiment, I will use an overall volume of 50 cm³ of 2moles of
to be done. This was to find out what amount of each liquid would be
The word dissolve means to mix and dissipate into a substance. In our data, compound A (ionic) rated a 3 on the scale of 0-4, 0 being not at all soluble, and 4 being completely dissolved. Compound B (covalent) rated a 0 on the same scale of solubility. This means that ionic compounds are more soluble than covalent compounds. I think that this is because of the positive and negative parts that make up an ionic bond. Since water molecules have both negative and positive parts, the atoms forming the ionic bonds would split up, and bond with other atoms. For example, if the ionic compound Sodium fluoride (Sodium+Fluorine) compound broke apart, Fluorine might bond with a hydrogen atom in the water. This is because Fluorine has 7 valence electrons and has a -1 charge and Hydrogen has 1 valence electron and a +1 charge. The two atoms combined would satisfy an octet (8
Water is a polar molecule. A water molecule has a negative pole exposed on the oxygen atom and two positive poles exposed on the hydrogen atoms. The negative ends of the hydrogen atoms bond with the positive end of the oxygen atom. Water molecules exist in a bent shape. This allows for water to be a universal solvent. Water can dissolve many common solids and liquids.
This would give us an extra measure of accuracy each time. Another way to improve the experiment and to produce consistent readings was to used distilled water. This is because the distilled water contains no impurities and therefore no hardness in water.
For the solubility test we were told to try and dissolve our unknown substance into water (H20), Sodium Hydroxide (NaOH), Hydrochloric Acid (HCl), Toluene, and Acetone. Our unknown substance was soluble in water, but not soluble in Toluene or Acetone.Our substance dissolved in water that means that it has to be some type of ionic compound. But, if our substance dissolved in Toluene, which is an organic solvent, then our substance would be non-polar. From these results we concluded that our substance was ionic because substances dissolve in other substances that are similar to it: “like dissolves like.” A substance will dissolve in something that it is similar to.
- The amount of times the mixture was stirred. We stirred the mixture until the Ammonium Nitrate was dissolved, so the amount of times we stirred after each teaspoon was different.
The solvents used in this experiment were sodium hydroxide as the aqueous layer and the ethyl acetate and unknown benzocaine as the organic phase. These phases are separated with an emulsion line which is a distinct line that shows where the aqueous and organic layers meet but do not mix. This method of separation relies on portioning the preferential dissolution of a compound into one solvent over another (2).
1-Butanol with intermediate polarity was soluble in both highly polar water and non polar hexane as 1-butanol can be either polar or non polar compound. 1-Butanol was polar based on the general rule of thumb stated that each polar group will allow up to 4 carbons to be soluble in water. Also, 1-butanol can be non polar due to their carbon chains, which are attracted to the non polarity of the hexane.
solute in a solvent. The ratio of the number of solute particles are a contributing factor, but not the types of particles. There are four main properties that are affected by this solute mass ratio, which include depression of freezing point, elevation of boiling point, lowering in vapor pressure, and osmotic pressure.
From these properties of bonds we will see that there are two fundamental types of bonds--covalent and ionic. Covalent bonding represents a situation of about equal sharing of the electrons between nuclei in the bond. Covalent bonds are formed between atoms of approximately equal electronegativity. Because each atom has near equal pull for the electrons in the bond, the electrons are not completely transferred from one atom to another. When the difference in electronegativity between the two atoms in a bond is large, the more electronegative atom can strip an electron off of the less electronegative one to form a negatively charged anion and a positively charged cation. The two ions are held together in an ionic bond because the oppositely charged ions attract each other as described by Coulomb's Law.
Firstly, we need to keep the chemical at a constant concentration. So, in this experiment we have chosen to keep hydrochloric acid at a constant concentration (5cm3). We could have, however, used Sodium Thiosulphate as a constant, but we had chosen to use Hydrochloric acid. Next, we must make sure that the solution is kept at a constant volume throughout the experiment. If the volume is different, then it could give different results if it was at a constant volume.