Consider this mechanism:

Katena32 [7]

Answer:

e. When the indicator changes color and remains, 2 more drops of the solution in the buret should be added.

Explanation:

Which statement is incorrect?

Select one:

a. The volume of solution in the buret should be recorded when the endpoint is reached. CORRECT. At the endpoint, the titrant is expected to have completely reacted with the titrand.

b. It is good practice to place the flask over a white background to better observe the color change of the solution. CORRECT. Using a white background makes it easier to detect the changes in the color of the indicator.

c. The endpoint is when the indicator changes color. CORRECT. This is the function of an indicator.

d. Phenolphthalein will go from a colorless solution to a pink solution for the addition of NaOH to an acid solution. CORRECT. Phenolphthalein is colorless when pH < 8.3 and it is pink when pH > 10.0.

e. When the indicator changes color and remains, 2 more drops of the solution in the buret should be added. INCORRECT. When the endpoint is reached, no more titrant should be added.

4 0

3 years ago

Suppose a group of volunteers is planning to build a park near a local lake. The lake is known to contain low levels of arsenic

ale4655 [162]

A) 10.75 is the concentration of arsenic in the sample in parts per billion .

B) 7,633.66 kg the total mass of arsenic in the lake that the company have to remove.

C)It will take 1.37 years to remove all of the arsenic from the lake.

Explanation:

A) Mass of arsenic in lake water sample = 164.5 ng

The ppb is the amount of solute (in micrograms) present in kilogram of a solvent. It is also known as parts-per million.

To calculate the ppm of oxygen in sea water, we use the equation:

$\text{ppb}=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 10^9$

Both the masses are in grams.

We are given:

Mass of arsenic = 164.5 ng = $164.5\times 10^{-9} g$

$1 ng=10^{-9} g$

Volume of the sample = V = $15.3 cm^3$

Density of the lake water sample ,d= $1.00 g/cm^3$

Mass of sample = M = $d\times V=1.0 g/cm^3\times 15.3 cm^3=15.3 g$

$ppb=\frac{164.5\times 10^{-9} g}{15.3 g}\times 10^9=10.75$

10.75 is the concentration of arsenic in the sample in parts per billion.

B)

Mass of arsenic in $1 cm^3$ of lake water = $\frac{164.5\times 10^{-9} g}{15.3}=1.075\times 10^{-8} g$

Mass of arsenic in $0.710 km^3$ lake water be m.

$1 km^3=10^{15} cm^3$

Mass of arsenic in $0.710\times 10^{15} cm^3$ lake water :

$m=0.710\times 10^{15}\times 1.075\times 10^{-8} g=7,633,660.130 g$

1 g = 0.001 kg

7,633,660.130 g = 7,633,660.130 × 0.001 kg=7,633.660130 kg ≈ 7,633.66 kg

7,633.66 kg the total mass of arsenic in the lake that the company have to remove.

C)

Company claims that it takes 2.74 days to remove 41.90 kilogram of arsenic from lake water.

Days required to remove 1 kilogram of arsenic from the lake water :

$\frac{2.74}{41.90} days$

Then days required to remove 7,633.66 kg of arsenic from the lake water :

$=7,633.66\times \frac{2.74}{41.90} days=499.19 days$

1 year = 365 days

499.19 days = $\frac{499.19}{365} years = 1.367 years\approx 1.37 years$

C)

Company claims that it takes 2.74 days to remove 41.90 kilogram of arsenic from lake water.

Days required to remove 1 kilogram of arsenic from the lake water :

$\frac{2.74}{41.90} days$

Then days required to remove 7,633.66 kg of arsenic from the lake water :

$=7,633.66\times \frac{2.74}{41.90} days=499.19 days$

1 year = 365 days

499.19 days = $\frac{499.19}{365} years = 1.367 years\approx 1.37 years$

It will take 1.37 years to remove all of the arsenic from the lake.

6 0

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Which of the following is an example of positive acceleration? Q A boy running from his house around the block and ending up bac

Natalija [7]

The answer is A track star speeding up as he sprints to the finish line.

8 0

3 years ago

Create an element card that has the following information:

Shtirlitz [24]

Answer:

Atomic number:6

Atomic mass:12.011

Chemical symbol:C

Name of element: Carbon, Carbone (french)

Image is in my explanation

Explanation:

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What is an organism that survives on a hist organism and cuases harm to the host

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An organisam is part of your body plant life

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