Fig. 1 shows a biogas digester on a dairy farm. Bacteria break down animal waste without oxygen. The gas bag stores methane and carbon dioxide. The digester...
Question 1 Report
Fig. 1 shows a biogas digester on a dairy farm. Bacteria break down animal waste without oxygen. The gas bag stores methane and carbon dioxide. The digester and bag are weighed together to monitor the conversion of organic carbon compounds into products.
(a) Name one gas in the gas bag that contains carbon. [1]
(b) Explain why the combined mass of the digester and gas bag stays constant. [2]
(c) Use the information that 2.4 kg of slurry produces 0.18 kg of gas. Calculate the mass of material remaining in the digester. [2]
A coastal rescue team inflates a life raft using a carbon dioxide cartridge. Fig. 1 shows the cartridge connected to the raft through a valve. The complete assembly is placed in a waterproof box on a balance during a safety test.
(a) Name the gas stored in the cartridge. [1]
(b) Describe the mass change of the cartridge alone as the raft inflates. [1]
(c) Explain why the mass of the sealed box and everything in it does not change. [2]
(d) What mass of gas is in the raft if the cartridge loses 0.62 g and no gas remains in the valve? [1]
Answer Details
Biogas digester
- One carbon-containing gas is methane or carbon dioxide. [1]
- The gases remain in the attached gas bag. Atoms from the slurry are rearranged into products, but none leave the combined digester-and-bag system, so its mass stays constant. [2]
- \[2.40\text{ kg}-0.18\text{ kg}=2.22\text{ kg}\]
Mass remaining = 2.22 kg. [2]
Life raft
- The cartridge contains carbon dioxide. [1]
- The cartridge's mass decreases as the raft inflates. [1]
- Carbon dioxide moves from cartridge to raft, but it remains inside the sealed box. Therefore no mass is lost from the complete system. [2]
- Mass of gas in raft = 0.62 g. [1]
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