Question

What is the mass of \[62.0\text{ mL}\] of ethanol? The density of ethanol at room temperature \[=\text{ }0.789\text{ }g/mL\] ?

Answer 1

Hint: We know that It can be calculated by the relation of heat transferred with the mass of an object. Theoretically, heat transferred is equal to the product of mass of object, specific heat of the object and change in temperature. By using this relation we will get the mass of ethanol. The formula here we will use is of density which is \[density(\rho )=\dfrac{mass}{volume}\]

Complete answer:
Also we know that a mole of anything contains $6.022\times {{10}^{23}}$ particles of molecules. For example, a mole of oxygen contains $6.022\times {{10}^{23}}$ oxygen particles; a mole of hydrogen contains $6.022\times {{10}^{23}}$ oxygen particles. Here, we need the formula of the number of moles.
Here, we have to calculate the volume which contains the same number of molecules as in 100 mL water. Same number of molecules present only when moles of ethanol and water are equal. The formula to calculate number of moles and now it is given that volume of ethanol is \[=62.0\text{ mL}\],that means \[V=62.0\text{ mL}\]
And it is also given that density of ethanol is \[=\text{ }0.789\text{ }g/mL\] now it means \[\rho =0.789\text{ gm}{{\text{L}}^{-1}}\]
Putting all values in formula of density which is \[density(\rho )=\dfrac{mass}{volume}\] we will get our answer which is \[\rho =\dfrac{m}{V}\]
Now by substituting the values we get;
\[0.789=\dfrac{mass\text{ of ethanol}}{62\times {{10}^{-3}}L}\]
On further solving this we will get our answer but here keep in mind that the volume should be in liters as the density is given in g/L and the mass we will get after calculation will be in grams not in kilograms as the unit of density is given in grams per liter. So our answer is
\[mass\text{ of ethanol=0}\text{.789}\times \text{62}\times \text{1}{{\text{0}}^{-3}}grams\]
On further simplifying we get;
\[mass\text{ of ethanol = 48}\text{.918}\times {{10}^{-3}}\text{ grams}\]

Note:
Remember that the combustion of a substance reacts rapidly with oxygen and produces heat. The substance which reacts rapidly with oxygen is called the fuel, and the source of oxygen is called the oxidizer. The fuel can be in the form of a solid, liquid, or gas. For example for airplane propulsion the fuel is usually a liquid. During the process of combustion, the fuel and oxidizer are turned into exhaust products, heat is generated.