I would say developed technologies which somehow were lost
like the stone age: the stone hammer, who used that afterwards in the roman empire era and stuff?
Answer:
Explanation:
True or false 4 questions help please!
Most mixtures are not physical changes.
True
False FALSE when I add solid NaCl salt to water I no longer have a solid salt, I have a solution of sodium and chlorid ions in liquid water. this is physical change
Chemical Changes do not create a new substance.
True
False FALSE 0ne of the proofs that you have a chemical change is the presence of a new substance
Fire is an example of a Chemical Change.
True TRUE fire is oxygen reacting wiIh mattter to form new compounds
False
Explosions are not chemical changes.
It depends on the explosion if I blow up a balloon until it POPS!! that is physical chame. If I light a firecracker and it explodes, that is a chemical change of oxygen reacting with hot gunpowder
A change in color and odor are both examples of chemical changi
I would rewrite the question as
A change in color and odor both INDICATE a chemical change
and that is
True TRUE
False
F
True Fire is an example of a Chemical Change.
True
False
Explosions are not chemical changes.
True
False
Answer:
C. The reaction can be broken down and performed in steps
Explanation:
Hess's Law of Constant Heat Summation states that irrespective of the number of steps followed in a reaction, the total enthalpy change for the reaction is the sum of all enthalpy changes corresponding to all the steps in the overall reaction. The implication of this law is that the change of enthalpy in a chemical reaction is independent of the pathway between the initial and final states of the system.
To obtain MgO safely without exposing magnesium to flame, the reaction sequence shown in the image attached may be carried out. Since the enthalpy of the overall reaction is independent of the pathway between the initial and final states of the system, the sum of the enthalpy of each step yields the enthalpy of formation of MgO.
Answer:
0.550
Explanation:
The absorbance (A) of a substance depends on its concentration (c) according to Beer-Lambert law.
A = ε . <em>l</em> . c
where,
ε: absorptivity of the species
<em>l</em>: optical path length
A 45 mM phosphate solution (solution A) had an absorbance of 1.012.
A = ε . <em>l</em> . c
1.012 = ε . <em>l</em> . 45 mM
ε . <em>l</em> = 0.022 mM⁻¹
We can find the concentration of the second solution using the dilution rule.
C₁ . V₁ = C₂ . V₂
45mM . 11mL = C₂ . 20.0 mL
C₂ = 25 mM
The absorbance of the second solution is:
A = (ε . <em>l</em> ). c
A = (0.022 mM⁻¹) . 25 mM = 0.55 (rounding off to 3 significant figures = 0.550)
In my opinion, the best answer among the choices listed above is the first option. The major reason for chemical bonding is <span>for atoms to gain the stability of the octet. In general, chemical reactions happen in order for substances achieve stability or appropriately achieve equilibrium.</span>
