Acids & Bases

• The pH scale is a range of numbers from 0-14, identifying if a solution is an acid, alkali, or neutral
• The pH scale is used for solutions (solids dissolved in water)
• Universal indicator or pH paper is used to measure pH
• The color of the resultant solution or the paper is matched to the pH scale to indicate how acidic or alkaline the solution is
• Acids have a pH number below 7 and give red, orange, or yellow colors with Universal Indicator
• Alkalis have a pH number above 7 and give blue or purple colors with Universal Indicator
• A neutral solution has a pH number of 7 and gives a green color with Universal Indicator
• Water and salt solutions are neutral solutions
• Non-metal oxides (carbon dioxide and sulfur dioxide) dissolve in water to form acidic solutions
• Metal oxides (calcium oxide and sodium oxide) dissolve in water to form alkaline solutions
• Oxides that don’t dissolve (like aluminium oxide) in water will be neutral as the pH of the water is unaffected
• Sulphur dioxide dissolves into rainwater and makes sulphurous acid, which then turns into sulphuric acid
• Nitrogen dioxide makes nitric acid
• Coal power stations, factories, house chimneys, cars, and oil refineries are the main producers of pollutant gases that cause acid rain
• Acid rain causes a lot of damage to buildings and wildlife
• Acids and alkalis have H+ ions and OH- ions, with the ratio between them determining the acidity or alkalinity of a solution
• Acidic solutions contain a higher concentration of H+ ions than OH- ions
• Neutral solutions contain equal concentrations of H+ ions and OH- ions
• All aqueous solutions (solid dissolved in water) have H+(aq) and OH-(aq) ions
• Water is neutral because it contains equal numbers of H+ and OH- ions due to a few water molecules breaking up
• Acids, alkalis, and water all slightly conduct electricity due to the ions they contain
• Concentration is how much of a solid is dissolved in a constant volume of liquid
• The more solid dissolved, the higher the concentration
• Diluting acid makes it less corrosive as its concentration decreases and the pH rises towards 7
• The concentration of a solution will not go past 7
• For alkalis, as their concentration decreases, the pH also decreases towards 7
• In a neutralization reaction, the pH of an acidic solution rises towards 7 when a base is added
• In a neutralization reaction, the pH of a base decreases towards 7, resulting in the formation of a salt and water
• Acid + Alkali react to form a salt and water