The Ancient Egyptians used simple sundials and divided days into smaller parts, and it has been suggested that as early as 1,500BC, they divided the interval between sunrise and sunset into 12 parts. ... Known as a clepsydra, it uses a flow of water to measure time.
A electrochemical reaction is said to be spontaneous, if
Answer 1:
Consider reaction: <span>Ni^2+ (aq) + S^2- (aq) ----> + Ni (s) + S (s)
The cell representation of above reaction is given by;
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Hence,

we know that,

and

Therefore,

= - 0.25 - (-0.47) = 0.22 v
Since,
is positive, hence cell reaction is spontaneous
.....................................................................................................................
Answer 2: Consider reaction: <span>Pb^2+ (aq) +H2 (g) ----> Pb (s) +2H^+ (aq)
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The cell representation of above reaction is given by;

Hence,

we know that,

and

Therefore,

= - 0.126 - 0 = -0.126 v
Since,
is negative, hence cell reaction is non-spontaneous.....................................................................................................................
Answer 3:
Consider reaction: <span>2Ag^+ (aq) + Cr(s) ---> 2 Ag (s) +Cr^2+ (aq)
</span>
The cell representation of above reaction is given by;

Hence,

we know that,

and

Therefore,

= - 0.22 - (-0.913) = 0.693 v
Since,
is positive, hence cell reaction is spontaneous
Answer:
The answer to your question is: CO2
Explanation:
The information given is correct, Covalent bonds occur when atoms share one or more pairs of electrons, but also, covalent bonds occur with nonmetals, then,
a.NaCl This elements form an ionic bond, so this option is incorrect.
b.Cl2 Here there are two non metals but the form one single covalent bond, so this option is incorrect.
c.CO2 Carbon dioxide forms 2 double covalent bonds.
d.NH3 ammonium only forms single covalent bonds
Answer:
D. Visible Light
Explanation:
D is the right answer because visible light is perceived by humans as color and the rest aren't visible at all. For example, if you broke a bone and have to have an X-ray done, you can't see the x-rays. When you are heating something in the microwave, you can't see the waves. And when you are listening to the radio in the car, you also can't see the waves.