Chemical reactions and equations

• Why do we store silver chloride in dark-coloured bottles?

  It reacts with light very fast and loses its property by forming chlorine gas and silver. So to avoid this, silver chloride in dark-coloured bottles. 
• Which of the gases is used to store fat and oil-containing foods for a long time?

  1. Carbon dioxide
  2. b) Oxygen
  3. c) Nitrogen
  4. d) Neon

  nitrogen
• What are the two chemical compounds used in black and white photography?

  Silver Bromide and Silver Chloride
• Which statements about the chemical reaction below are incorrect?-

  2PbO(solid) + C(s) →  2Pb(s) + CO2(g)

  (a) Lead is getting reduced

  (b) Carbon Dioxide CO2 is getting oxidised

  (c) Carbon is getting oxidised

  (d) Lead oxide is getting reduced

     (i) (a) and (b)

     (ii) (a) and (c)

     (iii) (a), (b) and (c)

     (iv) all

  option (i) (a) and (b)
• What is a chemical equation?

  A chemical equation is a representation of chemical reactions through symbols, letters and numbers
• What is respiration?

  Respiration is the process of burning food in the living body to produce energy. 
• Respiration - Chemical equation

  C6​H12​O6​+ 6O2​ → 6CO2​ + H2​O + energy (ATP)
• Types of decomposition reaction?

  Thermal decomposition

  Photolytic decomposition

  electrolytic decomposition
• The symbol for oxygen is O2.
• What is combination reaction?

  A reaction in which a single product is formed from two or more reactants is known as combination reaction
• CaO + H2O --> Ca(OH)2 + Heat

  Complete the reaction
• Finish the decomposition reaction:

  2FeSO4 --> Fe2O3 + SO2 + SO3
• Write a reaction for the heating of limestone:

  CaCO3 --> CaO + CO2
• A compound X present in a dry test tube is heated and produces brown fumes.

  Name compound X and the brown fumes

  Compound X is lead nitrate and the brown fumes are nitrogen dioxide
• A good example of an exothermic reaction is respiartion
• A reaction where oxygen is gained or hydrogen is lost, is known as oxidation reaction
• A reaction where oxygen is lost or hydrogen is gained is known as reduction reaction
• When both oxidation and reduction take place in a single chemical chemical reaction, it is known as redox reaction
• Rancidity takes place in fats and oils
• When fats and oils are left in the open for too long, they become rancid, inedible and produce foul smell. This is known as Rancidity
• Explain Corrosion

  Corrosion is the phenomenon in which metals deteriorate gradually in the presence of oxygen and air
• State the prevention methods for rancidity

  Adding antioxidants

  Storing food in airtight containers

  Replacing air by nitrogen

  refrigeration
• Prevention methods for corrosion

  Galvanization

  electroplating

  painting
• Why is it advised to clean a magnesium ribbon before burning it?

  Magnesium ribbon reacts with the atmospheric oxygen to form a layer of magnesium oxide which is a stable compound. To prevent further reactions with oxygen, it is therefore necessary to clean a magnesium ribbon before burning it
• Write a balanced chemical equation:

  Hydrogen + Chloride -- Hydrogen chloride

  H2 + Cl2 -- HCl
• Barium chloride + aluminium sulphate -- Barium sulphate + Aluminium Chloride

  3BaCl2 + Al(SO4)3 -- 3BaSO4 + 2AlCl3
• Sodium + water -- Sodium hydroxide + hydrogen

  2Na + 2H2o -- NaOH + H2