PMT

• What is a pure substance?

  A single element or compound
• Why are alloys harder than pure metals?

  They are mixtures of metals
• What is the purpose of the start line in paper chromatography?

  To spot the mixture for separation
• How is Rf calculated in chromatography?

  Distance moved by the spot / distance moved by solvent
• What does an Rf value of 0.85 indicate about a compound?

  It has a higher affinity for the solvent
• What happens when dilute acid is added to carbonate anions?

  Fizzing occurs as CO2 is released
• What is the equation for the reaction of sodium carbonate with hydrochloric acid?

  $Na_{2}CO_{3} +$$2 HCl \rightarrow 2 NaCl +$$H_{2}O +$$CO_{2}$
• Describe the test for sulfate anions and provide an equation.

  • Add Ba2+ solution (e.g., BaCl2)
  • White precipitate of BaSO4 forms
  • Equation: $K_{2}SO_{4} +$$BaCl_{2} \rightarrow 2 KCl +$$BaSO_{4}$
• What are instrumental methods in chemical analysis?

  Accurate, sensitive, and rapid methods
• What are cations and anions?

  Cations are positive ions; anions are negative ions
• What is affinity chromatography?

  Affinity chromatography is a method of separating a biomolecule from a mixture, based on a highly specific macromolecular binding interaction between the biomolecule and another substance.