Barium is a very reactive metal in the presence of oxygen and water, thus its density cannot be measured by water displacement. Instead, mesitylene (C9H12, density = 0.86370 g/mL (at 20 o C)) is used. 77.240 g of Ba is placed into a flask, and mesitylene is added so that together the total volume is 100.00 mL. The mass of the mesitylene and Ba together is 148.792 g. What is the density (in g/mL) of the Ba at 20 o C?

The correct answer is 4.502 g per ml.

Explanation:

Based on the given question, the sum of the mass of mesitylene and barium together is 148.792 grams. The mass of barium given is 77.240 grams. Therefore, the mass of mesitylene will be,  

Mass of mesitylene = Total mass - Mass of barium

= 148.792 - 77.240

= 71.552 grams

The density of mesitylene is 0.86370 g per ml. To calculate the volume of mesitylene, the formula to be used is,  

Volume = mass / density. Now, putting the values we get,  

Volume = 71.552 / 0.86370 = 82.8436 ml.  

As the total volume is 100 ml, therefore, the volume of Ba will be,  

Volume of Ba = 100-82.8436 = 17.1564 ml

The density of Ba at 20 degree C can be calculated by using the formula,  

Density = mass / volume. Now putting the values we get,  

Density = 77.240 g / 17.1564 ml  

= 4.502 g per ml

since electrons are negative the answer is neagtaive