Fig. 1 shows a gas-monitoring flask used by an environmental group beside a lake. A water sample is acidified so that dissolved carbonate releases carbon di...
Question 1 Report
Fig. 1 shows a gas-monitoring flask used by an environmental group beside a lake. A water sample is acidified so that dissolved carbonate releases carbon dioxide into a calibrated gas bag. The group wants to compare the amount of carbonate in water from two different streams.
Stream A produces 96.0 cm3 carbon dioxide and stream B produces 144 cm3, using equal volumes of water. At room conditions, molar gas volume is 24 dm3 mol-1. Assume each mole of carbonate produces one mole of carbon dioxide when acid is added.
(a) Calculate the amount, in mol, of carbon dioxide from stream A. [2]
(b) Use the information to calculate the amount, in mol, of carbonate in stream B. [2]
(c) Describe which stream contains more dissolved carbonate and use data to support your answer. [2]
Answer Details
The calculation uses \(n=\frac{V}{24}\) when gas volume is in dm3 and molar gas volume is \(24\text{ dm}^3\text{ mol}^{-1}\).
- Convert the volume first:
\[96.0\text{ cm}^3=0.0960\text{ dm}^3\]
\[n(\mathrm{CO_2})=\frac{0.0960}{24}=0.00400\text{ mol}\]
The amount of carbon dioxide from stream A is 0.00400 mol. [2] - \[144\text{ cm}^3=0.144\text{ dm}^3\]
\[n(\mathrm{CO_2})=\frac{0.144}{24}=0.00600\text{ mol}\]
Each mole of carbonate produces one mole of carbon dioxide, so the amount of carbonate in stream B is 0.00600 mol. [2] - Stream B contains more dissolved carbonate. Equal volumes of water were used, and B produced \(144\text{ cm}^3\) rather than \(96.0\text{ cm}^3\) of carbon dioxide, equivalent to \(0.00600\) mol rather than \(0.00400\) mol. [2]
Download The App On Google Playstore
Everything you need to excel in your exams
