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# Solving Real World Problems - PowerPoint PPT Presentation

Solving Real World Problems. WARM-UP : Chemists measure the acidity of a liquid by determining the concentration of the hydrogen ion (H + ) in the liquid. The acidity of a liquid on the pH scale is defined as: pH = -log [H + ] where [H + ] is the concentration of the hydrogen ion in mol/L.

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Presentation Transcript

WARM-UP:

Chemists measure the acidity of a liquid by determining the concentration of the hydrogen ion (H+) in the liquid.

The acidity of a liquid on the pH scale is defined as:

pH = -log [H+]

where [H+] is the concentration of the hydrogen ion in mol/L.

***TEST DATES***

Determine the pH of distilled water if it contains 10-7 mol/L of H+.

2. Determine the hydrogen ion concentration of a fruit juice with a pH of 3.10.

• Quantities that vary significantly are compared using a logarithmic scalesince a logarithmic scale is based on exponents.

• Note: If N=10000, then log10 104 = 4

• Therefore, using a logarithmic scale, 10000 is represented as 4.

• Logarithmic scales are applied to many real-life situations:

• Chemistry (the pH scale)

• Earthquakes (the Richter scale)

• Sound intensity (the decibel scale)

Dropping a measured volume of liquid into a solution changes the pH value from 4.2 to 3.5. How many times as acidic is a solution with a pH value of 3.5 than a solution with a pH value of 4.2?

Recall: pH = -log [H+]

Therefore: pH2 – pH1 = ( - log [H+]2 ) – ( -log [H+]1 )

The magnitude (strength) of an Earthquake is defined as:

where I is the intensity of the earthquake being measured and S is the standard intensity.

Earthquake B measures 4.5 on the Richter Scale while Earthquake A measures 7.5. How many times stronger is Earthquake A than B?

Earthquake A measures 6.9 on the Richter Scale. Calculate the magnitude of an earthquake with twice the intensity.

The decibel scale is used to measure the intensity of sound. The starting point of the scale, zero decibels, represents a sound minutely below that which the human ear can hear. The formula used to compare sound is:

where L is the intensity of the sound being sought, Lk is the intensity of the reference sound and y is the loudness in decibels.

A jet engine produces sound waves with a loudness of 100 dB. The ordinary household noise level is approximately 50 dB. How many times louder is the jet engine than an ordinary household noise?

• Unit 6 Workbook

• Complete the workbook!

• Exercise 5 (Page 13)

• MUST BE DONE BY TOMORROW’S CLASS!!