Fuel cells can make an electricity from a simple electrochemical
reaction in which oxygen and hydrogen combine to form water. There are several
different types of fuel cell but they are all based around a central design
which consists of two electrodes, a negative anode and a positive cathode.
These are separated by a solid or liquid electrolyte that carries electrically
charged particles between the two electrodes. A catalyst, such as platinum, is
often used to speed up the reactions at the electrodes. Fuel cells are
classified according to the nature of the electrolyte. Every type needs
particular materials and fuels and is suitable for any applications. The
article below uses the proton exchange membrane fuel cell to illustrate the
science and technology behind the fuel cell concept but the characteristics and
applications of the other main designs are also discussed. Proton Exchange Membrane Fuel Cells (PEMFC)
The hydrogen ions permeate across the electrolyte to the
cathode, while the electrons flow through an external circuit and provide
power. Oxygen, in the form of air, is supplied to the cathode and this combines
with the electrons and the hydrogen ions to produce water. These reactions at
the electrodes are as follows:
Anode: 2H24H+ + 4e-
Cathode: O2 + 4H+ + 4e- 2H2O
Overall: 2H2 + O22H2O + energy
PEM cells operate at a temperature of around 80°C. At this
low temperature the electrochemical reactions would normally occur very slowly
so they are catalysed by a thin layer of platinum on each electrode.
Answer:
Explanation:
The independent variable determines the value that needs to be calculated or the decision that needs to be made from the observations of the experiment. Hence, experimental design decision would most likely produce invalid and unreliable results when having more than one independent variable.
Explanation:
Ice crystals in meat signify that it is frozen,a bunch of water molecules within the food form to keep the meat hydrated .
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The answer is B
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Answer:
B Binary fission maintains genetic continuity because the daughter cells contain the same number of chromosomes as the parent cell.
Explanation:
Genetic continuity ensures that genetic information is passed from one generation to another in correct way so that the resultant progeny has the complete set of genes required for survival. For example, at the end of mitosis, daughter cells should have the same number of chromosomes as parent cell.
Binary fission is a method of reproduction in some organisms like bacteria. It is an asexual mode of reproduction in which the parent cell splits into daughter cells without the process of fusion with another cell. It still maintains genetic continuity because the daughter cells are identical to the parent cell and thus have same number of chromosomes and type of genes.
