Answer:
option (c)
Explanation:
According to the doppler's effect, the frequency of sound decreases.
If there is a relative motion between the source and the observer, the frequency of sound changes apparently.
the formula of the doppler effect is given by
where, f is the real frequency, v be the speed of sound, vo be the speed of the observer, here, the bus is the observer.
So, the value of f' < f
They have a negative oxidation number because nonmetals gain electrons, thus making them negatively charged ions (anions). Metals become cations and have a positive charge because they lose electrons.
To illustrate clearly, I will rewrite the reaction in a more understandable manner.
<span>2 Al(s) + Fe</span>₂O₃ (s) ⇒ 2 Fe(s) + Al₂O₃(s) Δ<span>hrxn = –850 kJ
This reaction has a negative sign for the change in enthalpy of reaction. The sign convention only means that the reaction releases energy to the surroundings. In other words, the reaction is exothermic. Focusing on only its magnitude, this means that 850 kJ of energy is needed for this reaction of 2 Aluminum moles and 1 mole of </span>Fe₂O₃ to occur.
Now, if you only had an energy of 725 kJ, then the reaction is incomplete but it will still form Iron (Fe). We use stoichiometric calculations as follows:
725 kJ * (2 mol Fe/850 kJ) = 1.7 moles of Fe
Knowing that the molar mass of Fe is 55.6 g/mol, then the mass of produced iron is
1.7 mol Fe * 55.6 g/mol = 94.85 g iron
The universe is made up of baryonic matter which is a combination of protons, electrons, and neutrons, and also dark matter and dark energy.
Galaxies are comprised of stars, while the universe is comprised of galaxies.
I hope my answer has come to your help. God bless and have a nice day ahead!
