Topics: PH indicator, PH, Acid Pages: 4 (833 words) Published: February 25, 2014
pH Indicators
pH indicators are weak acids that exist as natural dyes and indicate the concentration of H+ (H3O+) ions in a solution via color change. A pH value is determined from the negative logarithm of this concentration and is used to indicate the acidic, basic, or neutral character of the substance you are testing. Introduction

pH indicators exist as liquid dyes and dye-infused paper strips. They are added to various solutions to determine the pH values of those solutions. Whereas the liquid form of pH indicators is usually added directly to solutions, the paper form is dipped into solutions and then removed for comparison against a color/pH key.  

                    Very Acidic              Acidic                  Neutral            Basic           Very Basic    The Implications of the Indicated pH via the Equation
Recall that the value of pH is related to the concentration of H+ (H3O+) of a substance. pH itself is approximated as the cologarithm or negative logarithm of the H+ ion concentration (Figure 3). pH≈−log[H3O+](3)

A pH of 7 indicates a neutral solution like water. A pH less than 7 indicates an acidic solution and a pH greater than 7 indicates a basic solution. Ultimately, the pH value indicates how much H+ has dissociated from molecules within a solution. The lower the pH value, the higher concentration of H+ ions in the solution and the stronger the acid. Likewise, the higher the pH value, the lower the concentration of H+ ions in the solution and the weaker the acid.  How the Color Change of the Indicator Happens

The color change of a pH indicator is caused by the dissociation of the H+ ion from the indicator itself. Recall that pH indicators are not only natural dyes but also weak acids. The dissociation of the weak acid indicator causes the solution to change color. The equation for the dissociation of the H+ ion of the pH indicator is show below (Figure 4). ...
Continue Reading

Please join StudyMode to read the full document

You May Also Find These Documents Helpful

  • Essay about Hamas: a Conflict Within
  • Movements Essay Hamas
  • Lebanon: Israel-Hamas-Hezbollah Conflict Essay
  • Asymmetric conflict, Israel, Palestine (Hamas), etc. Essay
  • How to Handle Hamas Essay
  • Hamas Rise to Power and Transition Into Politics Essay
  • An Analysis of the Islamic Resistance Movement: Hamas Essay
  • Essay about To What Extent Does the Case of Hamas Prove or Disprove the View That Political Participation Leads to Moderation of a Radical...

Become a StudyMode Member

Sign Up - It's Free