chem imp questions

• Common characteristic of a covalent compound:

  • Consists of molecules
• Ammonium hydroxide will produce a reddish brown precipitate when added to a solution of:

  • CuSO4
• A salt which in solution gives a bluish white precipitate with NaOH solution and a white precipitate with BaCl2 solution is:

  • CuSO4
• Manufacture of ammonia:

  • Process: Haber process
  • Reactants ratio: 1:3
  • Catalyst used: Iron catalyst
  • Equation for the manufacture of ammonia: N2 + 3H2 -> 2NH3
  • Ammonia as a reducing agent: 2NH3 + 3O2 -> 2NO + 3H2O
• Identify the following substances:

  • An acidic gas which gives dense white fumes with NH3: HCl
  • An alkane with molecular mass 58: C4H10
  • A solid which forms a solution when kept in the open: Sugar
  • An alloy used in electrical fittings: Solder
  • A metal giving hydrogen gas with dilute acid and alkali: Zinc
• Equations for the following reactions:

  • Aluminium oxide and sodium hydroxide: Al2O3 + 2NaOH -> 2NaAlO2 + H2O
  • Zinc and dilute sulphuric acid: Zn + H2SO4 -> ZnSO4 + H2
  • Magnesium nitride and water: Mg3N2 + 6H2O -> 3Mg(OH)2 + 2NH3
  • Concentrated sulphuric acid and sugar: H2SO4 + C12H22O11 -> 12C + 11H2O + H2SO4
  • Copper with concentrated nitric acid: 3Cu + 8HNO3 -> 3Cu(NO3)2 + 2NO + 4H2O
• Naming:

  • Second member of the alkene series: Ethene
  • First member of the alkane series: Methane
  • Third member of the aldehyde series: Propanal
  • Second member of carboxylic acid: Ethanoic acid
  • Fourth member of the alcohol series: Butanol
• IUPAC names of the following compounds:

  • Not provided
• Particles present in a liquid compound which is a non-electrolyte: Molecules

  • Weak acid HX dilute solution particles: H+ and X-
  • Cations are formed by loss of electrons, and anions are formed by gain of electrons
  • Ions present in a solution for electroplating a metal: Metal cations
  • Electrolysis as an example of a redox reaction: Oxidation occurs at the anode, reduction at the cathode
• Electrolytic cell used in the extraction of aluminium:

  • Substance for electrodes A and B: Carbon
  • Aluminium formed at electrode: Cathode (B)
  • Aluminium compounds used as electrolyte C: Cryolite and Alumina
  • Electrode B needs continuous replacement due to erosion
• Zinc extraction from zinc blende:

  • Zinc compound in zinc blende: ZnS
  • Equation for roasting of zinc blende: 2ZnS + 3O2 -> 2ZnO + 2SO2
  • Purpose of using coke: Reducing agent
  • Reducing agent used in the extraction: Carbon (from coke)
• Ammonium hydroxide distinguishing between:

  • Iron (II) chloride and iron (III) chloride: Iron (II) chloride forms a green precipitate with NH4OH, while iron (III) chloride forms a reddish-brown precipitate
  • Zinc sulphate and lead nitrate: Zinc sulphate forms a white precipitate with NH4OH, while lead nitrate forms a yellow precipitate
  • Lead hydroxide and zinc hydroxide: Lead hydroxide forms a brown precipitate with NH4OH, while zinc hydroxide forms a white precipitate
• Method for preparation of salts:

  • Sodium nitrate: Neutralisation
  • Iron (III) chloride: Direct synthesis
  • Lead chloride: Double decomposition
  • Zinc sulphate: Neutralisation
  • Sodium hydrogen sulphate: Decomposition by acid
• Balanced chemical equations:

  • Basic oxide + acid -> salt + water: CaO + H2SO4 -> CaSO4 + H2O
  • Metallic carbonate + acid -> salt + water + carbon dioxide: ZnCO3 + 2HCl -> ZnCl2 + H2O + CO2
• Type of bonding in:

  • Ammonia: Covalent
  • Calcium oxide: Ionic
  • Methane: Covalent
• Group of elements in the periodic table:

  • Most metallic character: Thallium
  • Highest electronegativity: Boron
  • Electrons in outer shell of Thallium: 3
  • Compound formed when Boron reacts with chlorine: BCl3
  • Elements to the right of Boron group more metallic: Less metallic due to increasing non-metallic character
• Anhydrous HCl vs. aq. HCl conductivity: Anhydrous HCl is covalent and does not ionize, while aq. HCl ionizes into H+ and Cl- ions for conductivity
• Reasons:

  • Fumes when opening HCl bottle: HCl gas reacts with moisture in the air to form misty droplets
  • White fumes with NH4OH and HCl gas: Formation of NH4Cl solid
  • Dry HCl vs. wet litmus paper: Dry HCl is non-ionized, while wet HCl forms H+ ions turning blue litmus red
• Hydrogen chloride gas collection:

  • Hydrogen chloride gas is acidic and soluble in water, forming hydrochloric acid
• Electroplating with nickel:

  • Electrolyte: Nickel sulfate solution
  • Cathode: Keychain
  • Anode: Nickel electrode
  • Cathode reaction: Ni2+ + 2e- -> Ni
  • Anode reaction: Ni -> Ni2+ + 2e-
• Chemistry is the study of matter, its properties, composition, and the changes it undergoes
• Matter is anything that has mass and occupies space
• Elements are pure substances that cannot be broken down into simpler substances by chemical means
• Compounds are substances composed of two or more elements chemically combined in fixed proportions
• Mixtures are combinations of two or more substances that are physically mixed but not chemically combined
• Atoms are the basic units of matter and are composed of protons, neutrons, and electrons
• The periodic table is a chart that organizes elements based on their atomic number and chemical properties
• Chemical reactions involve the breaking and forming of chemical bonds between atoms
• Acids are substances that release hydrogen ions in solution, while bases release hydroxide ions
• The pH scale measures the acidity or basicity of a solution, ranging from 0 (most acidic) to 14 (most basic)
• Organic chemistry focuses on the study of carbon-containing compounds
• Inorganic chemistry deals with compounds that do not contain carbon
• Chemical equations represent the reactants and products of a chemical reaction using chemical formulas
• Balancing chemical equations ensures that the law of conservation of mass is obeyed
• The mole is a unit used to measure the amount of a substance, with one mole containing Avogadro's number of particles
• The study of chemistry is essential for understanding the world around us and for various applications in industries and daily life
• Strong acids completely dissociate into their component ions when they dissolve in water, while weak acids only partially dissociate.
• Acids are proton donors (hydrogen ion donors) while bases are proton acceptors (hydrogen ion acceptors).
• The pH scale is logarithmic, meaning that a change of one unit on the pH scale represents a tenfold increase or decrease in acidity.
• Ionic compounds have high melting points due to the strong electrostatic forces between oppositely charged ions.