What color do acids and bases turn litmus paper?
Litmus indicator solution turns red in acidic solutions and blue in alkaline solutions - and it turns purple in neutral solutions. Litmus paper is usually more reliable, and comes as red litmus paper and blue litmus paper. The table shows the colour changes it can make.
Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F). Neutral litmus paper is purple.
- It also makes damp red litmus paper turn blue. Ammonia forms a white smoke of ammonium chloride when hydrogen chloride gas, from concentrated hydrochloric acid, is held near it.
- A strong acid- strong base titration is performed using a phenolphthalein indicator. Phenolphtalein is chosen because it changes color in a pH range between 8.3 – 10. It will appear pink in basic solutions and clear in acidic solutions.
Indicators are organic substances that change colours at certain pH values. In order to determine whether a substance is an acid or base you must use both red and blue litmus paper. This is mainly to determine if the substance is neutral because the paper will stay the same colour in both.
- Thus, salts consisting of these ions are neutral salts. For example: NaCl, KNO3, CaBr2, CsClO4 are neutral salts. When weak acids and bases react, the relative strength of the conjugated acid-base pair in the salt determines the pH of its solutions. The salt, or its solution, so formed can be acidic, neutral or basic.
- General Characteristics of Bases:
- pH > 7.
- Bitter taste.
- Slippery feel.
- Increases the OH- concentration in water.
- Accepts OH- ions.
- Turns red litmus indicator blue.
- Phenolphthalein is another commonly used indicator for titrations, and is another weak acid. In this case, the weak acid is colourless and its ion is bright pink. Adding extra hydrogen ions shifts the position of equilibrium to the left, and turns the indicator colourless.
Acid - Base indicators (also known as pH indicators) are substances which change colour with pH. They are usually weak acids or bases, which when dissolved in water dissociate slightly and form ions. Consider an indicator which is a weak acid, with the formula HIn.
- Acid - Base indicators (also known as pH indicators) are substances which change colour with pH. They are usually weak acids or bases, which when dissolved in water dissociate slightly and form ions. Consider an indicator which is a weak acid, with the formula HIn.
- Bases have a pH greater than 7 and can accept a proton or produce an OH- ion in a reaction. Now, if you had more acid than base in this reaction, not all of the acid would react, so the result would be salt, water, and leftover acid, so the solution would still be acidic (pH < 7 ).
- An endpoint is indicated by some form of indicator at the end of a titration. An equivalence point is when the moles of a standard solution (titrant) equal the moles of a solution of unknown concentration (analyte).
Updated: 2nd October 2019