Answer:
the answer is A) carbon
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Answer:
The nichrome wire is dirty.
The solution is contaminated.
Explanation:
If the nichrome wire is dirty, it may contain sodium contaminants which may be responsible for the yellow flame. The nichrome wire is first inserted into the flame without the sample to check for impurities.
The test solution may also have been contaminated. This leads to the appearance of a colour different from the expected colour of the test cation in the solution.
Answer:
A. The lens spreads light.
Explanation:
The convex lens will converge the light that passes through it. The direction of light will be bend to be closer to the middle point. This is the lens used for the eyeglass that treat people with hypermetropia. That is why the convex lens also called a converging lens or a plus lens. The strength of the convex lens depends on its focal length, index of the material used, and the radius of curvature.
Explanation:

The value of
:
![K_w=[H^+][OH^-]](https://tex.z-dn.net/?f=K_w%3D%5BH%5E%2B%5D%5BOH%5E-%5D)
a. pOH = 3.51
The sum of pH and pOH is equal to 14.
pH + pOH = 14 (at 25°C)
pH = 14 - 3.51 = 10.49
The pH of the solution is defined as negative logarithm of hydrogen ion concentration in solution.
![pH=-\log[H^+]](https://tex.z-dn.net/?f=pH%3D-%5Clog%5BH%5E%2B%5D)
![10.49=-\log[H^+]](https://tex.z-dn.net/?f=10.49%3D-%5Clog%5BH%5E%2B%5D)
![[H^+]=3.2\times 10^{-11}](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3D3.2%5Ctimes%2010%5E%7B-11%7D)
is the
concentration for an aqueous solution with pOH = 3.51 at 25°C.
b.
At a certain temperature, the pH of a neutral solution is 7.56.
Neutral solution means that concentration of hydrogen ion and hydroxide ions are equal.
![[H^+]=[OH^-]](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3D%5BOH%5E-%5D)
![7.56=-\log[H^+]](https://tex.z-dn.net/?f=7.56%3D-%5Clog%5BH%5E%2B%5D)
![[H^+]=2.754\times 10^{-8} M](https://tex.z-dn.net/?f=%5BH%5E%2B%5D%3D2.754%5Ctimes%2010%5E%7B-8%7D%20M)
The value of
at at this temperature:
![K_w=[H^+][OH^-]](https://tex.z-dn.net/?f=K_w%3D%5BH%5E%2B%5D%5BOH%5E-%5D)
![K_w=[H^+][H^+]](https://tex.z-dn.net/?f=K_w%3D%5BH%5E%2B%5D%5BH%5E%2B%5D)

The value of
at at this temperature is
.