Fig. 1 shows an automated dispenser filling small bottles with a glucose solution for a hospital training exercise. The stock solution has concentration 0.4...
Question 1 Report
Fig. 1 shows an automated dispenser filling small bottles with a glucose solution for a hospital training exercise. The stock solution has concentration 0.400 mol dm-3. Each bottle must receive 50.0 cm3 containing 0.0100 mol of glucose. The display gives the volume delivered by the pump.
(a) Use the amount of glucose and the concentration of stock solution to calculate the volume of stock solution needed, in dm3. [2]
(b) Give this volume in cm3. [1]
(c) Describe how water is used after the stock solution has been delivered to make the final volume correct. [2]
A chemist prepares aluminium nitrate solution for an etching test on a metal surface. Fig. 1 shows the labelled storage bottle and the volumetric flask used. The bottle must be labelled clearly because aluminium nitrate is a compound, not the metal aluminium. The required solution contains 0.0750 mol of Al(NO3)3 in 300 cm3 of solution.
(a) Use the information to calculate the concentration of aluminium nitrate in mol dm-3. [2]
(b) Give the unit used for molar concentration. [1]
(c) Describe one safety step when transferring this solution to the labelled bottle. [2]
Answer Details
Glucose dispenser
(a) Use \(V=\frac{n}{c}\):
\[V=\frac{0.0100}{0.400}=0.0250\text{ dm}^3\]
The required stock-solution volume is 0.0250 dm3. [2 marks]
(b)
\[0.0250\text{ dm}^3=25.0\text{ cm}^3\]
The volume is 25.0 cm3. [1 mark]
(c) After delivering the stock solution, add water until the total volume is exactly 50.0 cm3. Mix thoroughly so the glucose concentration is even throughout the bottle. [2 marks]
Aluminium nitrate solution
(a)
\[300\text{ cm}^3=0.300\text{ dm}^3\]
\[c=\frac{0.0750}{0.300}=0.250\text{ mol dm}^{-3}\]
The concentration is 0.250 mol dm-3. [2 marks]
(b) The unit for molar concentration is mol dm-3. [1 mark]
(c) Wear eye protection and use a funnel to avoid spills. Clearly label the bottle with the chemical identity and hazard information, and clean up any spill promptly. Any two valid safety steps gain credit. [2 marks]
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