Q. 2.18 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify the numbers in each of the following statements as measured or exact:

(a) There are $31$ students in the laboratory.

(b) The oldest known flower lived $1.20\times {10}^8 yr$ ago.

(c) The largest gem ever found . an aquamarine , has a mass of  $104 kg$.

(d) A laboratory test shows a blood cholesterol level of $184 mg/dL$.

Step-by-Step Solution

Answer

(a) Exact, as it denotes number of students .

(b) Measured, as it shows the  time period of oldest known flower.

(c) Measured, as it denotes the mass of largest gem.

(d) Measured, as it is laboratory test for blood cholesterol level.

Part(a) Step1 : Given information.

We have been given that there are $31$ students in the laboratory.

We need to state whether this statement is measured or exact.

Part(a) Step2 : Simplify.

 Exact. Since it denotes number of students in laboratory , therefore it is exact. Number is always exact .

Part(b) Step1 : Given information.

We have been given that the oldest flower lived $1.20\times {10}^8 yr$ ago.

We need to state whether this statement is measured or exact.

Part(b) Step2 : Simplify.

Measured. Since it denotes the time period of the oldest flower that lived many yrs ago ,therefore it measured by carbon dating method. This method is not exact but give approximate idea about age.

Part(c) Step1 : Given information.

We have ben given that the largest gem ever found, an aquamarine, has a mass of $104 kg$.

We need to state whether this statement is measured or exact.

Part(c) Step 2: Simplify.

Measured. Since it is mass, therefore it has been measured . Mass is fundamental quantity of matter , hence it is always measured .

Part(d) Step1 : Given information.

We have been given that a laboratory test shows a blood cholesterol level of$184 mg/dL.$

We need to state whether this statement is measured or exact.

Part(d) Step2 : Simplify.

Measured. Since it shows laboratory test for blood cholesterol level therefore , it has been  measured. Laboratory test performed ,has always some error so ,it can not be exact.