Because this denominator ranges drastically, it is convenient to use a logarithmic scale. This is known as the pH scale. You can use pH to make a quick determination of whether a given water based solution is acidic, basic, or neutral.
The table below gives the typical pH values of some common substances. Note that several food items are on the list, and most of them are acidic. You need to determine how to evaluate the above expression on your calculator. Ask your instructor if you have any questions. The other issue that concerns us here is significant figures. Because the number s before the decimal point in a logarithm relate to the power on 10, the number of digits after the decimal point is what determines the number of significant figures in the final answer.
Depending on the calculator you use, the method for solving this problem will vary. In any case, the correct numerical answer is as follows:. Most of the examples in the text examined growing quantities, but linear and exponential equations can also describe decreasing quantities, as the next few problems will explore. Pure water, with a pH of 7, is neutral. With a pH of less than 7, wine is acidic.
Exercises Marko currently has 20 tulips in his yard. Each year he plants 5 more. Write a recursive formula for the number of tulips Marko has Write an explicit formula for the number of tulips Marko has Pam is a Disc Jockey.
Every week she buys 3 new albums to keep her collection current. She currently owns albums. A population of beetles is growing according to a linear growth model. After how many weeks will the beetle population reach ? The number of streetlights in a town is growing linearly.
How many months will it take to reach lights? Write a recursive formula for the population of Tacoma Write an explicit formula for the population of Tacoma If this trend continues, what will Tacoma's population be in ? Portland's population in was about thousand, and had been growing by about 1. Write a recursive formula for the population of Portland Write an explicit formula for the population of Portland If this trend continues, what will Portland's population be in ?
Diseases tend to spread according to the exponential growth model. In , about people in the U. If the trend had continued unchecked, how many people would have died from AIDS in ? The population of the world in was 5 billion and the annual growth rate was estimated at 2 percent per year.
Assuming that the world population follows an exponential growth model, find the projected world population in A bacteria culture is started with bacteria. After 4 hours, the population has grown to bacteria. The signal produced by the bulb is amplified and sent to an electronic meter connected to the bulb, which measures and display the pH reading. It gives more precise values than the pH papers. For very precise measurement, the pH meter should be calibrated before each measurement.
The calibration should be performed with at least two buffer solutions with known pH. For general purposes, buffer solutions with pH 4 and pH 10 are used. For more precise measurements, three buffer solution calibrations are preferred. After each single measurement, the bulb is rinsed with distilled water or deionised water to remove any traces of solution being measured.
Then the bulb is blotted with a blotting paper to remove remaining water that could dilute the sample and alter the reading. When not in use, the bulb must be kept wet at all times to avoid dehydration of the pH sensing membrane. This is a blue-violet coloured liquid. When it comes in contact with acidic substances, it becomes red.
When it comes in contact with basic substances, it becomes green or even yellow. Cite this Simulator:. Determination of pH.
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Chemistry Terminology: Definition of pOH. How to Calculate the pH of a Weak Acid. List of the Strong Acids and Key Facts. Chemistry Scavenger Hunt Clues and Answers. Arrhenius Acid Definition and Examples.
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