Introduction

Members: Arthur Chong, Jeremy Sim, Royce Teo, Chong Tinghao
Title: Investigation of the effect of acid on iron.

1.1    Question being addressed
Our group would like to know under what level of pH or Molarity would create the optimal conditions for the corrosion of iron.  
Iron will be used as it is common in daily use, such as at home, transportation, and being part of an alloy (steel). 


Corrosion/Rusting is equivalent to the iron losing weight, therefore, to calculate the rate of corrosion, (original weight - weight after rusting)/time exposed to acidification. (T. Bell, 2015)



1.2 Hydrochloric Acid
It is used in the manufacture of phosphoric acid, chlorine dioxide, ammonium chloride, fertilisers, dyes, and artificial silk and pigments for paints. It is used as a refining ore in the production of tin and tantalum, as a lab reagent, and as a metal treating agent. It is used to remove scale and dust from boilers and heat exchange equipment, to clean membranes in desalination plants, to increase oil well output, to prepare synthetic rubber products by treating isoprene, and to clean and prepare other metals for coatings. It is used in the neutralisation of waste streams, the recovery of zinc from galvanised iron scrap, the production of chloride chemicals, the production of vinyl chloride from acetylene and alkyl chlorides from olefins, the manufacture of sodium glutamate and gelatine, the conversion of cornstarch to syrup, sugar refining, electroplating, soap refining, leather tanning, and the photographic, textile, brewing, and rubber industries. It is used to maintain pH balance in swimming pools, spas, etc. It is also used as a bactericide, a fungicide, and a veridic to disinfect bathrooms, kitchens and food preparation areas, and other areas in commercial and industrial buildings, in hospitals, in nursing homes, and in and around household dwellings. It is used in food processing as a starch modifier. (Australian Government, 2015)

1.3 Sulphuric Acid
Sulphuric acid is one of the most important industrial chemicals. More of it is made each year than is made of any other manufactured chemical; more than 40 million tons of it were produced in the United States in 1990. It has widely varied uses and plays some part in the production of nearly all manufactured goods. The major use of sulphuric acid is in the production of fertilisers, e.g., superphosphate of lime and ammonium sulphate. It is widely used in the manufacture of chemicals, e.g., in making hydrochloric acid, nitric acid, sulphate salts, synthetic detergents, dyes and pigments, explosives, and drugs. It is used in petroleum refining to wash impurities out of gasoline and other refinery products. Sulphuric acid is used in processing metals, e.g., in pickling (cleaning) iron and steel before plating them with tin or zinc. Rayon is made with sulphuric acid. It serves as the electrolyte in the lead-acid storage battery commonly used in motor vehicles (acid for this use, containing about 33% H2SO4 and with specific gravity about 1.25, is often called battery acid). (Pearson Education, 2015)

1.4 Citric Acid
Citric acid can be added to ice cream as an emulsifying agent to keep fats from separating, to caramel to prevent sucrose crystallisation, or in recipes in place of fresh lemon juice. Citric acid is used with sodium bicarbonate in a wide range of effervescent formulae, both for ingestion (e.g., powders and tablets) and for personal care (e.g., bath salts, bath bombs, and cleaning of grease). Citric acid is also often used in cleaning products and sodas or fizzy drinks.Citric acid is an excellent chelating agent, binding metals. It is used to remove limescale from boilers and evaporators.It can be used to soften water, which makes it useful in soaps and laundry detergents. By chelating the metals in hard water, it lets these cleaners produce foam and work better without need for water softening. Citric acid is the active ingredient in some bathroom and kitchen cleaning solutions. A solution with a 6% concentration of citric acid will remove hard water stains from glass without scrubbing. In industry, it is used to dissolve rust from steel. Citric acid can be used in shampoo to wash out wax and colouring from the hair. (Wikipedia, 9 January 2015)


1.5 Hypothesis:
  1. The more concentrated the acid, the more rust formed on the metal.
  2. The sulphuric acid has the highest rate of corrosion.
1.6 Independent variable:
  • The type of acid
  • Concentration of acid
1.7 Dependant variable:
  • The rust on the metal
  • The weight of the metal
1.8 Constant variable:
  • The duration of the metal in the acid
  • The exposed surface area of the metal to the acid
  • Amount of acid used


1.9 How is our Hypothesis related to our experiment?
Our first hypothesis is to find out if the molarity (concentration) of the acid is higher, the more rust formed on the metal. Hence, if we were to complete our experiment, we will be able to see the effects caused and also, we will be able to find out if our first hypothesis is true. And while doing our experiment, we will be able to identify if our second hypothesis is true.

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