Carbon disulfide (CS₂) boils at 46.30 °C and has a density of 1.261 g/mL. (a) When 0.250 mol of a nondissociating solute is dissolved in 400.0 mL of CS₂, the solution boils at 47.46 °C. What is the molal boiling-point-elevation constant for CS₂?

Video transcript

Hello everyone. Today, we are being given the following problem and asked to solve for it. It says a solution containing 0.200 100 moles of a non volatile non dissociating salute and 400 g of fennel boils at 183.47 degrees Celsius. If pure funnel boils at 181.7 degrees Celsius, calculate the below Skopje constant KB for final. So the first thing you wanna do is you want to find what our boiling point of the solution will be. So we're going to take the boiling point of the pure salt. We're going to equal that to our boiling point of the solution plus the total boiling point that we have. We can abbreviate that as TB. We already know that the Temperature of the non volatile non associating salute will be 183.47°C. And we also know that the female boils at a temperature of 181.7°C. And now we simply just have to solve for TB. Through some quick calculations, we get that TB is equal to 1.77°C. And they were going to plug that into our boiling point elevation equation which says that our boiling point elevation is going to be equal to m or moles morality times our KB. And so if you pull in our Values, we have 1.77°C. We're going to equal that to our morality which is our moles over kg and in this case we have 0.2 moles over 0.4 kg. We took this 400 g and we converted that to kilograms by using the conversion factor that one g is equal to 10 to the negative third kilograms. To get 0.4 kg we have our KB that we have yet to solve for. And so when we rearrange this equation and solve for K B, we get, K B is equal to 3.54, there is Celsius over our morality. And that is our final answer. I hope this helped and until next time.