Answer:
Hydrogen reacts with oxygen to produce water, which releases energy.
Explanation:
In any fuel cell chemical bonds are formed and energy is released . It is a redox reaction . Bond energy is converted into electrical energy.
In the given option , first option is not possible because methane reacts with oxygen to give carbon dioxide and water .
third and fourth option are ruled out because chemical reactions are using energy . No energy is released . so they are not possible.
Here
Part B - 2
Answer all questions in this part. Directions (51 - 65): Record your answers in the spaces provided in your answer booklet. Some questions may require the use of the 2011 Edition Reference Tables for Physical Setting/Earth Science. Base your answers to questions 51 and 52 on the diagram and data table below, and on your knowledge of Earth science. The diagram represents the laboratory materials used for an investigation of the effects of particle size on water retention. Five separate columns were filled to the same level with particles. The particle type is indicated for each column. The particles within each column are of uniform shape. A volume of 50 milliliters (mL) of water was poured through each column, and the amount of water retained was determined. The data table shows the results of this experiment.
Answer: time taken to charge to 95%
t = -5.80[ln(1-0.95)]
t = 17.38ms
Explanation:
For an RC Charging circuit
Where Vs
Vc = Vs (1 - e^(-t/RC))
Vc/Vs = 1 - e^(-t/RC)
-t/RC = ln(1 - Vc/Vs)
t = -RC[ln(1 - Vc/Vs)] and RC = k = -t/ln(1 - Vc/Vs)
Where ;
Vc = voltage across the capacitor
Vs = voltage supply
t = charging time = 2.5ms
k = RC = time constant.
Vc/Vs = 0.35
To calculate the time constant k;
k = -t/ln(1- Vc/Vs)
k = -2.5/ln(1-0.35)
k = 5.80ms
time taken to charge to 95%
t = -5.80[ln(1-0.95)]
t = 17.38ms
I'm not too sure about this but unit is definitely one of the answers. If "number" refers to (for example) the "6" in 6 inches then it should also count. I think "symbol" could also just be unit so I'm not sure about that.
Among the elements in group 7A, the most reactive would be Fluorine. Fluorine is a major component of toothpaste, what we use to brush and clean our teeth with. It is so reactive that it cannot be contained in glass.
