Litmus paper and phenolphthalein indicators have pH range limitations and lack precision. Universal indicator and bromothymol blue are alternative indicators that offer a broader range and greater accuracy.
Litmus paper is a pH indicator that changes color in the presence of an acid or a base. However, it can only indicate whether a substance is acidic (turns red) or basic (turns blue), without providing an accurate pH value. Phenolphthalein, on the other hand, is colorless in acidic solutions and pink in basic solutions, but it has a limited pH range of 8.2 to 10.0.
To overcome these limitations, the universal indicator is commonly used. It is a mixture of several indicators that produces a wide range of colors depending on the pH of the solution. The resulting color can be compared to a color chart to determine the approximate pH value of the substance being tested. This allows for a more precise measurement of pH compared to litmus paper or phenolphthalein.
Another alternative indicator is bromothymol blue. It changes color depending on the pH of the solution, from yellow in acidic solutions to blue in basic solutions. Bromothymol blue has a pH range of 6.0 to 7.6, which makes it suitable for a broader range of pH measurements compared to phenolphthalein.
These alternative indicators, universal indicator and bromothymol blue, provide a wider pH range and more precise measurements compared to litmus paper and phenolphthalein. They offer greater versatility and accuracy in determining the acidity or basicity of a solution.
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The standard molar enthalpy change for this reaction is -1.3 MJ. What is the enthalpy change when 6 moles of octane are combusted
The enthalpy change when 6 moles of octane are combusted is -7.8 MJ. This value is obtained by multiplying the standard molar enthalpy change (-1.3 MJ/mol) by the number of moles of octane combusted.
The balanced combustion equation for octane (C8H18) is:
C8H18 + 12.5O2 → 8CO2 + 9H2O
According to the balanced equation, the stoichiometric coefficient of octane is 1, which means that the enthalpy change for the combustion of 1 mole of octane is -1.3 MJ.
To find the enthalpy change when 6 moles of octane are combusted, we can multiply the standard molar enthalpy change by the number of moles of octane:
Enthalpy change = -1.3 MJ/mol * 6 mol
Enthalpy change = -7.8 MJ
Therefore, when 6 moles of octane are combusted, the enthalpy change is -7.8 MJ.
The enthalpy change when 6 moles of octane are combusted is -7.8 MJ. This value is obtained by multiplying the standard molar enthalpy change (-1.3 MJ/mol) by the number of moles of octane combusted. The negative sign indicates that the combustion process is exothermic, releasing energy in the form of heat.
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