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notsponge [240]
3 years ago
6

Which is the best pure substance gold or air?

Chemistry
2 answers:
Elena L [17]3 years ago
7 0
Gold is the best pure substance. The answer is gold
ehidna [41]3 years ago
7 0
It is gold!!!!!!!!!!!!!!!!!!
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For a particular redox reaction, Cr is oxidized to CrO 2 − 4 and Ag + is reduced to Ag . Complete and balance the equation for t
Sunny_sXe [5.5K]

Answer:

6Ag⁺ + Cr + 8OH⁻ → 6Ag + CrO₄²⁻ + 4H₂O

Explanation:

We can balance the redox reaction of Cr and Ag⁺, in terms of two half-reactions, one for Ag⁺ and other for Cr:

Ag⁺   →   Ag      

In the above equation we need to balance the number of electrons, we know that the Ag⁺ is being reduced to Ag, so the reaction is:

Ag⁺ + e⁻ →  Ag   (1)

Now, we need to balance the half-reaction of Cr:

Cr   →  CrO₄²⁻  

From above, we know that the Cr is being oxidated to CrO₄²⁻, so we need to balance the number of electrons and the number of oxygen atoms. The Cr⁰ is being oxidated to Cr⁶⁺, so for the electron balance, we need to add 6e⁻ to the right side of the equation. Since the reaction is in a basic medium, the oxygen atoms will be balanced with OH⁻ ions as follows:          

Cr + OH⁻ →  CrO₄²⁻ + 6e⁻  

The hydrogen atoms will be balanced using H₂O molecules:  

Cr + OH⁻ →  CrO₄²⁻ + 6e⁻ + H₂O    

The balanced equation is:

Cr + 8OH⁻ →  CrO₄²⁻ + 6e⁻ + 4H₂O   (2)

Since the reaction (1) involves 1 electron and the reaction (2) involves 6 electrons, by increasing the reaction (1) six times and by the addition of the two reactions (1 and 2) we can have the net redox reaction:

6*(Ag⁺ + e⁻ →  Ag)  

<u>Cr + 8OH⁻ →  CrO₄²⁻ + 6e⁻ + 4H₂O</u>

6Ag⁺ + Cr + 8OH⁻ → 6Ag + CrO₄²⁻ + 4H₂O                  

Therefore, the net equation is: 6Ag⁺ + Cr + 8OH⁻ → 6Ag + CrO₄²⁻ + 4H₂O.

I hope it helps you!

7 0
4 years ago
A gecko used its sticky feet to crawl from the bottom of a window to the top of
sp2606 [1]

Answer:

Decreased

Explanation:

You're faster when you go downhill than you are uphill.

8 0
3 years ago
What type of Machine is a handrail
Elodia [21]
Hey There!

Here is your answer:

The answer is a compound machine!

Hope this helps!
4 0
3 years ago
Different microscopic organisms cause different
lozanna [386]

Answer/Explanation:

A theory has lots of scientific evidence to back it up. We know this to be true based on lots of different diseases and studies of their spread.

A hypothesis is more of a starting point - an educated guess based on limited evidence. It requires further testing before becoming a theory.

A law is something that can be generalized to lots of contexts, and is universal. Such as the law of thermodynamics.

5 0
3 years ago
Can DDT only be synthesized one way?
son4ous [18]

Answer:

DDT (dichloro-diphenyl-trichloroethane) was developed as the first of the modern synthetic insecticides in the 1940s. It was initially used with great effect to combat malaria, typhus, and the other insect-borne human diseases among both military and civilian populations. It also was effective for insect control in crop and livestock production, institutions, homes, and gardens. DDT's quick success as a pesticide and broad use in the United States and other countries led to the development of resistance by many insect pest species.

Regulation Due to Health and Environmental Effects

The U.S. Department of Agriculture, the federal agency with responsibility for regulating pesticides before the formation of the U.S. Environmental Protection Agency in 1970, began regulatory actions in the late 1950s and 1960s to prohibit many of DDT's uses because of mounting evidence of the pesticide's declining benefits and environmental and toxicological effects. The publication in 1962 of Rachel Carson's Silent Spring stimulated widespread public concern over the dangers of improper pesticide use and the need for better pesticide controls.

In 1972, EPA issued a cancellation order for DDT based on its adverse environmental effects, such as those to wildlife, as well as its potential human health risks. Since then, studies have continued, and a relationship between DDT exposure and reproductive effects in humans is suspected, based on studies in animals. In addition, some animals exposed to DDT in studies developed liver tumors. As a result, today, DDT is classified as a probable human carcinogen by U.S. and international authorities.

DDT is:

known to be very persistent in the environment,

will accumulate in fatty tissues, and

can travel long distances in the upper atmosphere.

After the use of DDT was discontinued in the United States, its concentration in the environment and animals has decreased, but because of its persistence, residues of concern from historical use still remain.

Current Status

Since 1996, EPA has been participating in international negotiations to control the use of DDT and other persistent organic pollutants used around the world. Under the auspices of the United Nations Environment Programme, countries joined together and negotiated a treaty to enact global bans or restrictions on persistent organic pollutants (POPs), a group that includes DDT. This treaty is known as the Stockholm Convention on POPs. The Convention includes a limited exemption for the use of DDT to control mosquitoes that transmit the microbe that causes malaria - a disease that still kills millions of people worldwide.

In September 2006, the World Health Organization (WHO) declared its support for the indoor use of DDT in African countries where malaria remains a major health problem, citing that benefits of the pesticide outweigh the health and environmental risks. The WHO position is consistent with the Stockholm Convention on POPs, which bans DDT for all uses except for malaria control.

DDT is one of 12 pesticides recommended by the WHO for indoor residual spray programs. It is up to individual countries to decide whether or not to use DDT. EPA works with other agencies and countries to advise them on how DDT programs are developed and monitored, with the goal that DDT be used only within the context of programs referred to as Integrated Vector Management. EXIT IVM is a decison-making process for use of resources to yield the best possible results in vector control, and that it be kept out of agricultural sectors.

Explanation:

hope this helps

6 0
3 years ago
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