(a) The pH of a cold drink is 5. What will be its action on blue and red litmus solutions?
(b) The pH values of three acids A, B and C having equal molar concentrations are 5.0, 2.8 and 3.5 respectively. Arrange these acids in order of the increasing acid strengths.
(a) The cold drink turns blue litmus red because of its acidic nature (pH=5). It will show no action on red litmus solution.
(b) Acids arranged in order of the increasing acid strengths are A
Acid values are considered when pH is less than 7. B has a maximum acid strength because pH is inversely proportional to the concentration of hydrogen ions in a solution.
pH Scale is used to measure acidity or alkalinity of water-soluble substances (pH stands for 'potential of Hydrogen'). It measures H+ concentration in a solution.
- The pH scale ranges from 0 to 14.
- A pH less than 7 is acidic in nature.
- A pH of 7 is neutral.
- A pH greater than 7 is basic in nature.
The pH of a solution is a measure of the molar concentration of hydrogen ions in the solution and as such is a measure of the acidity or basicity of the solution.
The letters pH stand for "power of hydrogen" and the numerical value for pH is just the negative of the power of 10 of the molar concentration of H+ ions.
To calculate the pH of an aqueous solution you need to know the concentration of the hydronium ion in moles per litre (molarity).
The pH is then calculated using the expression: pH = - log [H3O+]. ]
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- A student measured the pH values of four solutions A, B, C and D which were found to be 4, 1, 13 and 11 respectively. Which of the following statements are correct about these solutions?(a) A is strong acid and B is weak acid (b) B is strong acid and D is weak base (c) D is strong base and C is weak base (d) C is strong base and A is weak acid (1) (a) and (b) (2) (b) and (c) (3) (c) and (d) (4) (b) and (d)
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- Fill in the following blanks with suitable words:(a) Acids have a pH ______ than 7.(b) Alkalis have a pH _____ than 7.(c) Neutral substances have a pH of _____.(d) The more acidic a solution, the _____ the pH.(e) The more alkaline a solution, the ______ the pH.
- In an experiment to measure the pH values of solutions, a student placed strips of universal indicator paper in four beakers containing solutions A, B, C and D. The colour of universal indicator paper in these solutions is as shown below :The solution having lowest pH value is:(1) A(2) B(3) C(4)D"
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