From the periodic table:
molecular mass of carbon = 12 grams
molecular mass of fluorine = 18.99 grams
molecular mass of chlorine = 35.5 grams
Therefore:
one mole of CF2Cl2 = 12 + 2(18.99) + 2(35.5) = 120.98 grams
Therefore, we can use cross multiplication to find the number of moles in 79.34 grams as follows:
mass = (79.34 x 1) / 120.98 = 0.6558 moles
Now, one mole contains 6.022 x 10^23 molecules, therefore:
number of molecules in 0.65548 moles = 0.6558 x 6.022 x 10^23
= 3.949 x 10^23 molecules
Answer:
D.
Explanation:
Translation:
A. make a barbecue
B. organize a picnic
C. swimming in the pool
D. to go skiing
Barbecue is usually a summer activity, so we eliminate that.
It would be too cold for a picnic!
It would be too cold to go swimming, and that's more of a summer thing!
Skiing is a snow activity, and since it is winter, it is likely to know.
<h2> The correct option is (a).</h2>
Explanation:
- There is no change of state in pouring water into a vacuum insulated bottle as the vacuum created inside the bottle only reduces the time limit for the transfer of heat by conduction and convection.
- It helps the content filled in the bottle to be hot and cool for a longer time.
Hence, option (a) is correct.
Rest of the options (b), (c), (d), (e) is not correct because of the following reasons:
- In the sublimation of dry ice, the dry ice (solid-state) is changed to the vapour form.
- In the freezing of water, the liquid state is changed to solid-state.
- During the vaporization of alcohol, the liquid state is changed to the vapour form.
- During the melting of ice, the solid-state is changed to the liquid state.
<span>During cooling, the kinetic energy of the molecules falls, be</span>cause, when cooling a substace, the particles (molecules) slow down.
The kinetic energy is related to the speed, such that the lower speed the lower kinetic energy.
Particles can translate and vibrate, in the case of gases and liquids, and only vibrate (in the case of solids).
As a substance is cooled the particles get closer and the motion (translation and vibration), slows down. You can see by the equation of the kinetic energy (KE):
KE = [1/2]mass×(speed)² that as the speed is lower the KE will also be lower.
Additionally, when the cooling does not drive a change of phase (gas to liquid, liquid to solid, or solid to gas), it drives a decrease on temperature. In this case you should know that the temperature is a measure of the kinetic energy: the lower the temperature, the lower the kinetic energy.
Answer:
the reactivity of alkaline earth metals increases from top to the bottom of the group, that's because the atoms get bigger from the top to the bottom so the valence electrons are farther from the nucleus.
