In aqueous solution, Cd2+will precipitate out of solution in the form of CdS in the presence of
hydrogen sulfide (H2S). The Ksp of CdS = 1.0 x 10-28 and Ksp of H2S = 1.0 x 10-26 for the
reaction: H2S (aq) = 2 H+(aq) + S2-(aq)
a. Write the balanced net ionic equation for the reaction of cadmium ion with hydrogen sulfide
to form cadmium sulfide solid.
b. Write the equilibrium expression for the equation in part a.
c. Calculate Koverall for the reaction in part a.
d. Calculate the [Cd2+] in a solution saturated with H2S (0.10 M) at a pH = 2.00 ([H+] = 0.010
M).
Solution
a) The balanced ionic equation for the formation of cadmium sulfide from cadmium ion and
hydrogen sulfide is given as
Cd2+ (aq) + H2S (aq) <=======> CdS (s) + 2 H+ (aq) ……..(1)
b) The equilibrium constant for the reaction is given as
Koverall = [H+]2/[Cd2+][H2S] (ans)
Note that the concentration of a solid is not written in the expression for the equilibrium
constant.
c) Write down the two ionization reactions as below.
CdS (s) <=======> Cd2+ (aq) + S2- (aq) ……..(2)
Ksp = [Cd2+][S2-]
H2S (aq) <=======> 2 H+ (aq) + S2- (aq) …….(3)
Ka = [H+]2[S2-]/[H2S]
Subtract (2) from (3) and obtain
Cd2+ (aq) + H2S (aq) <======> CdS (s) + 2 H+ (aq)
Koverall = [H+]2/[Cd2+][H2S] = ([H+]2/[H2S])*(1/[Cd2+])
= ([H+]2[S2-]/[H2S])*1/([Cd2+][S2-]
= Ka*1/Ksp
= (1.0*10-26)*1/(1.0*10-28) = 100 (ans).
d) We have [H2S] = 0.10 M and pH = 2.00.
We define pH as pH = -log [H+]
====> 2.00 = -log [H+]
====> [H+] = antilog (-2.00) = 0.01 M
Since Ka (H2S) is extremely small, we may assume the equilibrium concentration of H2S to be
equal to 0.10 M; hence, we have
Koverall = [H+]2/[Cd2+][H2S]
====> 100 = (0.01)2/[Cd2+].(0.10)
====> [Cd2+] = (0.01)2/(100*0.10) = 1.0*10-5
The concentration of Cd2+ at equilibrium is 1.0*10-5 M (ans)..
IPV6 is the replacement for IPV4. This shows a lack of vision when t.pdf
1. IPV6 is the replacement for IPV4. This shows a lack of vision when the Internet was created.
Why do you think this statement is correct or incorrect? The IoT (Internet of Things) is a current
buzzword. How do you participate in the IoT personally? How do you think IPV6 will support
the IoT, and what visions do think engineers should consider
Solution
The Internet may be a world network comprising several voluntarily interconnected
autonomous networks. It operates while not a central organization. The technical underpinning
and standardization of the core protocols IPv4 and IPv6 is an activity of the web Engineering
Task Force IETF a non-profit organization of loosely related international participants that
anyone could come with by contributory technical experience. to take care of ability, the
principal name areas of the web square measure administered by the web Corporation for allotted
Names and Numbers ICANN ICANN is ruled by a global board of administrators drawn from
across the web technical, business, academic, and alternative non-commercial communities.
ICANN coordinates the assignment of distinctive identifiers to be used on the web, together with
domain names, web Protocol IP addresses, application port numbers within the transport
protocols, and lots of alternative parameters. Globally unified name areas square measure
essential for maintaining the world reach of the web. This role of ICANN distinguishes it as
maybe the sole central coordinative body for the world web. IP addressing is one amongst the
foremost difficult aspects of TCP/IP. It will leave even the foremost seasoned network directors
scratching their heads. as luck would have it, the Network+ communicating needs solely a basic
information of informatics addressing. The subsequent sections examine however informatics
addressing works for each IPv4 and also the newest version of IP: IPv6. To communicate on a
network victimization TCP/IP, every system should be allotted a singular address. The address
defines each variety of the network to that the device is connected and also the number of the
node thereon network. In alternative words, the informatics address provides 2 items of
knowledge. It’s a trifle sort of a street name and house variety in an exceedingly person’s home
address. Each device on a logical network section should have a similar network address as all
the opposite devices on the section. All the devices thereon network section should then have
totally different node addresses. In informatics addressing, another set of numbers, referred to as
a subnet mask, defines that portion of the informatics address refers to the network address and
that refers to the node address. IP addressing is totally different in informaticsv4 and IPv6. The
discussion begins by watching IPv4.
