Q. 2.22 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify each of the following as measured or exact and give the number of significant figures (SFs) in each measured number: 

a. An adult with the flu has a temperature of $103.5 °F$.

b. A blister (push-through) pack of prednisone contains $21$ tablets

c. The time for a nerve impulse to travel from the feet to the brain is $0.46$ s.

d. A brain contains $1.20\times 100$ neurons.

Step-by-Step Solution

Answer

(a) An adult with the flu has a temperature of $103.5 °F$ is measured.

(b) A blister (push-through) pack of prednisone contains $21$ tablets is exact.

(c) The time for a nerve impulse to travel from the feet to the brain is $0.46$ s is measured.

(d)  A brain contains $1.2\times 100$ neurons is measured.

Part a: Step 1: Given Information

We have been given that an adult with the flu has a temperature of $103.5 °F$. 

Part a: Step 2: Explanation

Measured numbers are the results of measuring a quantity such as our height or distance. Due to measurement techniques, their values aren't exact.

An exact number can be calculated with absolute accuracy. They can't be simplified or reduced. 

Here, it is a measured number and there are four significant digits.

Part b: Step 1: Given Information

We have been given that a blister (push-through) pack of prednisone contains $21$ tablets 

Part b: Step 2: Explanation

Measured numbers are the results of measuring a quantity such as our height or distance. Due to measurement techniques, their values aren't exact.

An exact number can be calculated with absolute accuracy. They can't be simplified or reduced. 

Here, it is an exact number.

Part c: Step 1: Given Information

We have been given that the time for a nerve impulse to travel from the feet to the brain is $0.46$ s. 

Part c: Step 2: Explanation

Measured numbers are the results of measuring a quantity such as our height or distance. Due to measurement techniques, their values aren't exact.

An exact number can be calculated with absolute accuracy. They can't be simplified or reduced. 

Here, it is a measured number and there are two significant digits.

Part d: Step 1: Given Information

We have been given that brain contains  neurons. 

Part d: Step 2: Explanation

Measured numbers are the results of measuring a quantity such as our height or distance. Due to measurement techniques, their values aren't exact.

An exact number can be calculated with absolute accuracy. They can't be simplified or reduced. 

Here, it is a measured number and there are two significant digits.