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General Chemistry Principles, Patterns, and Applications, 2011

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Solution:<br />

a. ln(0.523) = −0.648; e −0.648 = 0.523<br />

b. ln(1.63) = 0.489; e 0.489 = 1.63<br />

S K I L L BUILDER ES2<br />

What number is each value the natural logarithm of?<br />

a. 2.87<br />

b. 0.030<br />

c. −1.39<br />

Solution:<br />

a. ln x = 2.87; x = e 2.87 = 17.6 = 18 to two significant figures<br />

b. ln x = 0.030; x = e 0.030 = 1.03 = 1.0 to two significant figures<br />

c. ln x = −1.39; x = e −1.39 = 0.249 = 0.25<br />

Calculations with Natural Logarithms<br />

Like common logarithms, natural logarithms use the properties of exponents. We can exp<strong>and</strong> Table 4.5<br />

"Relationships in Base-10 Logarithms" in Essential Skills 3 to include natural logarithms:<br />

Operation Exponential Form Logarithm<br />

Multiplicatio<br />

n<br />

Division<br />

Inverse<br />

(10a)(10b) = 10a + b<br />

(ex)(ey) = ex + y<br />

10a10b = 10a - bexey = ex - y<br />

log(ab) = log a + log b<br />

ln(exey) = ln(ex) + ln(ey) = x + y<br />

log(ab) = log a - log bln (xy)<br />

= ln x - ln yln(exey) = ln(ex) - ln(ey) = x - y<br />

log(ab) = log a - log bln (xy)<br />

= ln x - ln yln(exey) = ln(ex) - ln(ey) = x - y<br />

log(1a) = -logaln(1x) = -ln x<br />

The number of significant figures in a number is the same as the number of digits after the decimal point<br />

in its logarithm. For example, the natural logarithm of 18.45 is 2.9151, which means that e 2.9151 is equal to<br />

18.45.<br />

S K I L L BUILDER ES3<br />

Calculate the natural logarithm of each number.<br />

a. 22 × 18.6<br />

0.512.67 c. 0.079 × 1.485<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

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