Question

What is the mass of a $15mL$ sample of mercury, if the density of mercury (liquid) = $13.55gc{m^{ - 3}}$
Options-
$A)$ $209$
$B)$ $203$
$C)$ $208$
$D)$ $231$

Answer 1

In order to solve this question, we should know about the density formula. Also, the units and its conversions should be known. Each substance has a specific density. Density is defined as mass per unit volume.

Complete answer:
Density is a characteristic property of each substance. In simple words density is the measurement of how tightly matter is packed together. It is the relationship between the mass of the substance and how much volume it takes up. It should be noted that substances with the same volume but different mass have different densities.
Density of an object is expressed as;
$Density = \dfrac{{mass}}{{volume}}$
It is usually represented by ‘’ $\rho$ ‘’
Now coming to our question;
Density $(\rho )$ of mercury (liquid) is given = $13.55gc{m^{ - 3}}$
Volume of the sample is also given = $15mL$
And we have to find the mass-
We can use the density formula to find the mass of the sample.
$mass = density \times volume$
Before putting the values in the formula, we have to check the units if they are not equal then one should do the conversion. In this case density is in $gc{m^{ - 3}}$ while the volume is in $mL$ .
But, $1mL = 1c{m^3}$
Thus no need to do the conversion.
Putting the values in the formula;
$mass = 13.55gc{m^{ - 3}} \times 15c{m^3}$
$mass = 203.25g$
The mass of the sample was found to be $203.25g$ . which is closer to option B
So, the correct answer is “Option B”.

Note:
We found the mass of the sample by using the density formula. It should be noted that the S.I unit of density is $Kg{m^{ - 3}}$ . But usually we use $g{L^{ - 1}}$ for gases, $gc{m^{ - 3}}$ for solids and $g{(mL)^{ - 1}}$ for liquids.