Answer:
Carbon dioxide
Explanation:
Neither helium nor carbon dioxide has a molecular dipole, so their strongest van der Waals attractive forces are London forces.
Helium is a small spherical atom with only a two electrons, so its atoms have quite weak attractions to each other.
CO₂ is a large linear molecule. It has more electrons than helium, so the attractive forces are greater. Furthermore, the molecules can align themselves compactly side-by-side and maximize the attractions (see below).
For example. CO₂ becomes a solid at -78 °C, but helium must be cooled to -272 °C to make it freeze (that's just 1 °C above absolute zero).
Il fait plus chaud à l'équateur et plus froid aux pôles car : 1°) les rayons du Soleil sont plus concentrés au niveau de l'équateur et plus diffus au niveau des pôles ; 2°) l'épaisseur d'air composant l'atmosphère, traversée par les rayons du Soleil est plus importante aux pôles qu'à l'équateur.
Answer:
7,94 minutes
Explanation:
If the descomposition of HBr(gr) into elemental species have a rate constant, then this reaction belongs to a zero-order reaction kinetics, where the r<em>eaction rate does not depend on the concentration of the reactants. </em>
For the zero-order reactions, concentration-time equation can be written as follows:
[A] = - Kt + [Ao]
where:
- [A]: concentration of the reactant A at the <em>t </em>time,
- [A]o: initial concentration of the reactant A,
- K: rate constant,
- t: elapsed time of the reaction
<u>To solve the problem, we just replace our data in the concentration-time equation, and we clear the value of t.</u>
Data:
K = 4.2 ×10−3atm/s,
[A]o=[HBr]o= 2 atm,
[A]=[HBr]=0 atm (all HBr(g) is gone)
<em>We clear the incognita :</em>
[A] = - Kt + [Ao]............. Kt = [Ao] - [A]
t = ([Ao] - [A])/K
<em>We replace the numerical values:</em>
t = (2 atm - 0 atm)/4.2 ×10−3atm/s = 476,19 s = 7,94 minutes
So, we need 7,94 minutes to achieve complete conversion into elements ([HBr]=0).
solution:
Physical properties describe how a material looks. such as color, state of matter, shininess, Other physical properties include density, mp, bp, brittleness, malleability, conductivity, ductility, solubility in water. A physical property can be determined without changing the identity of the material.
Chemical properties describe how a material behaves.such as does it burn, does it corrode, does it react with air, does it react with water, does it act like a metal by giving away electrons o like a nonmetal by taking electrons, what type of bonds will it form, or is it inert, is it acidic or basic, Chemical properties can only be determined during a chemical reaction.
