Lecture 2: Solutions Flashcards
- Define mixture, solution, solvent and solute.
A mixture is a combination of molecules that are not dissolved. A solution is a homogeneous mixture in which one substance (solute) is dissolved in another substance (solvent). The substance that dissolves the solute in a solution is called as the solvent. The substance that gets dissolved in the solvent in a solution is called as the solute.
- What differentiates an electrolyte solution from a non-electrolyte solution?
An electrolyte solution has dissolved ions. A non-electrolyte solution has dissolved molecules.
- When 1g of nanoparticles of gold are mixed with water, what kind of solution do you get? And what if water is mixed with NaCl nanoparticles instead?
a suspension an electrolyte solution
- Is it possible to have a solid solution? Give at least one example.
is a solid-state solution of one or more solutes in a solvent. It is different to a compound as the crystal structure of the solvent remains unchanged by addition of the solutes. Steel is one.
- What would generate dipoles in molecules?
One atom attracts electrons more than the other and so one becomes more negative while the other becomes more positive.
- What is a hydrogen bond and how are they formed? Give two examples.
A hydrogen bond is a primarily electrostatic force of attraction between a hydrogen atom which is covalently bound to a more electronegative atom or group electronegative ba
- Why does the curvature of the meniscus in a flask face outside liquid water and the inverse applies to liquid mercury?
Formation of meniscus depends on cohesive and adhesive forces in a liquid. In water adhesive forces >than the cohesive forces. In mercury cohesive forces < adhesive forces.
- Which solution with polymers would be more viscous: one with short chain or long chain polymers? Why?
long chain molecules have more intermolecular forces therefore would be more viscous.
- What is molar solubility and how can you get a saturated solution of any compound?
Molar solubility is the number of moles of a substance (the solute) that can be dissolved per liter of solution before the solution becomes saturated. Add solute to liquid until dissolving stops. or Evaporate a solvent from a solution until the solute begins to crystallise or precipitate.
- What is a surfactant? Give some examples of where they can be found.
A surfactant is a molecule that has a hydrophobic and a hydrophilic part so that a lipid and water can be combined.
- Based on the equation ΔG = ΔH – TΔS, what would you say determines the dissolution of a compound?
Dissolving depends on the balance between the increase in entropy of the solution and the increase in entropy of the surroundings
- When does a chemical reaction reach equilibrium and how you can determine this experimentally?
Chemical reactions reach a state of dynamic equilibrium in which the rates of forward and reverse reactions are equal and there is no net change in composition.
- What is activity and what is the activity of a pure compound.
In chemical thermodynamics, activity (symbol a) is a measure of the “effective concentration” of a species in a mixture, taking into consideration the interactions between solvent and solute by an empirical constant γi activity coefficient. activity a = 1 for a pure compound.
- Given the chemical reaction aA(g) + bB(g) ⇌ cC(g) + dD(g), what would be the equilibrium constant? And if instead the equation was: aA(s) + bB(g) ⇌ cC(g) + dD(g)
k1=cC(g)+dD(g)/aA(g)+bB(g) Generally, we assume that pure solid and liquid components have been eliminated from an equilibrium expression. so aA(s)=0 K2 = cC(g)+dD(g) / bB(g)
- Based on thermodynamics, what can you say about a reaction that has K<1 and one that has K>1?
K < 1 for endothermic reaction K > 1 for exothermic reaction
- How should you determine a rate law for a reaction?
- three reactions. Initial concentrations in first reaction. the second doubles the first and the third doubles the second reactant. 2. determine the power to which the reactants increase. and place in reaction with the powers.
