Question

Baking soda and vinegar are mixed to form carbon dioxide gas according to the reaction below; the gas is collected at 21oC in an inverted graduated cylinder over water.

NaHCO₃(s) + HC₂H₃O₂(aq) → CO₂(g) + H₂O(l) + NaC-2H-3O-2(aq)

In order to determine the pressure of CO2 in the cylinder, the vapor pressure of water at 21oC must be ______.
a) 17.5 torr
b) 20.0 torr
c) 23.8 torr
d) 25.5 torr

Answer 1

The vapor pressure of water at 21°C is needed to calculate the total pressure of CO2 gas collected over water. The closest given value to the known vapor pressure of water at this temperature is 20.0 torr, although actual reference materials should be checked for the precise value.

Step-by-step explanation:

To determine the pressure of CO2 collected in a cylinder during the reaction between baking soda (sodium bicarbonate) and vinegar (acetic acid), the vapor pressure of water at the given temperature must be known as CO2 is collected over water. This vapor pressure is essential for calculating the total pressure inside the cylinder using Dalton's Law of Partial Pressures, which states that the total pressure is the sum of the partial pressures of the individual gases present.

The vapor pressure of water at 21°C (295 K) is commonly found in reference materials or water vapor tables. According to known data, the vapor pressure of water at 21°C is 18.65 torr. Therefore, the closest value to this known vapor pressure in the options provided is 20.0 torr (b), although actual references should be checked for precise values as they can vary slightly based on the source.