What is the mass (in grams) of 500 mL of ethanol? (density of ethanol = 0.789 g/mL)

1. Analyze the question

You are asked to calculate the mass of a substance (ethanol) given its volume and its density.

• Volume ($V$): 500 mL
• Density ($\rho$): 0.789 g/mL
• Required: Mass ($m$) in grams.

2. Explain the concept

In chemistry and physics, density is defined as the mass per unit volume of a substance. The relationship is expressed by the formula:

To find the mass, we rearrange the formula:

3. Show the solution

Using the values provided:

• $\rho = 0.789 \text{ g/mL}$
• $V = 500 \text{ mL}$

Substitute these into the rearranged formula:

(Note: The unit "mL" cancels out, leaving the result in grams.)

4. Identify the answer

Comparing our result to the given options: A. 394.5 mL (Incorrect unit) B. 500 mL (Incorrect unit and value) C. 394.5 g (Correct value and unit) D. 500 g (Incorrect value)

5. Tip

Always check the units before selecting your final answer. In this question, options A and B are in milliliters (volume), while C and D are in grams (mass). Since the question asks for mass, you can immediately eliminate any options that do not end in grams (g). This is a quick way to narrow down your choices in JAMB exams!