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I am Lyosha [343]

3 years ago

7

Which statement is incorrect?

1 answer:

Katena32 [7]3 years ago

4 0

Answer:

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

Explanation:

<em>Which statement is incorrect? </em>

<em>Select one: </em>

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

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

<em>c. The endpoint is when the indicator changes color.</em> CORRECT. This is the function of an indicator.

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

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

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10. If 3.5 kJ of energy are added to a 28.2 g sample of iron at 20°C, what

igor_vitrenko [27]

Answer:

569K

Explanation:

Q = 3.5kJ = 3500J

mass = 28.2g

∅1 = 20°C = 20 + 273 = 293K

∅2 = x

c = 0.449

Q = mc∆∅

3500 = 28.2×0.449×∆∅

3500 = 12.6618×∆∅

∆∅ = 3500/12.6618

∆∅ = 276.4220

∅2 - ∅1 = 276.4220

∅2 = 276.4220 + ∅1

∅2 = 276.4220 + 293

∅2 = 569.4220K

∅2 = 569K

3 0

3 years ago

Analysis of the water content of a lake found in the desert showed that it contained 17.5 percent chloride ion, and has a densit

tankabanditka [31]

Answer:

The molarity is 6.0 M.

Explanation:

<em>The </em><em>concentration</em><em> of a solution is the amount of solute present in a given amount of solvent, or a given amount of solution.</em>

In this problem, we are asked to convert percent by mass to molarity, which are two different concentration units.

<em>The </em><em>percent by mass </em><em>is the ratio of the mass of a solute to the mass of the solution, multiplied by 100 percent.</em> On the other hand, <em>molarity (M)</em><em> is defined as the number of moles of solute per liter of solution.</em>

If we have 17.15 percent chloride ion, that means that we have 17.15 grams of chloride ion in 100 grams of solution. The density provided is the density of the solution, so we calculate how many mL correspond to 100 grams of solution:

1.23 g ----------- 1 mL

100 g ------------ <u>x= 81.3 mL</u>

Therefore, 17.5 grams of chloride ion are contained in 81.3 mL. Now we need to convert these grams into moles.

The atomic mass of chlorine is 35.5 g/mol:

35.5 g --------------- 1 mol

17.5 g --------------- <u>x= 0. 49 mol</u>

This 0.49 moles are contained in 81.13 mL, the definition of molarity says that this moles are contained in a liter (or what is the same, 1000 mL):

81.3 mL --------------- 0.49 mol

1000 mL ------------- x= 6.0 M

The molarity of the chloride ion will be 6.0 M.

5 0

3 years ago

After substantial heating, 6.25 g of iron produced 18.00 g of a compound with chlorine. The empirical formula is:

babunello [35]

Answer:

Option A. FeCl3

Explanation:

The following data were obtained from the question:

Mass of iron (Fe) = 6.25g

Mass of the compound formed = 18g

From the question, we were told that the compound formed contains chlorine. Therefore the mass of chlorine is obtained as follow

Mass of chlorine (Cl) = Mass of compound formed – Mass of iron.

Mass of chlorine (Cl) = 18 – 6.25

Mass of chlorine (Cl) = 11.75g

The compound therefore contains:

Iron (Fe) = 6.25g

Chlorine (Cl) = 11.75g

The empirical formula for the compound can be obtained by doing the following:

Step 1:

Divide by their molar mass

Fe = 6.25/56 = 0.112

Cl = 11.75/35.5 = 0.331

Step 2:

Divide by the smallest

Fe = 0.112/0.112 = 1

Cl = 0.331/0.112 = 3

The empirical formula for the compound is FeCl3

3 0

3 years ago

The gas in a sealed container has an absolute pressure of 125.4 kilopascals. If the air around the container is at a pressure of

AlexFokin [52]

Answer: C. 25.6 kPa

Explanation:

The Gauge pressure is defined as the amount of pressure in a fluid that exceeds the amount of pressure in the atmosphere.

As such, the formula will be,

PG = PT – PA

Where,

PG is Gauge Pressure

PT is Absolute Pressure

PA is Atmospheric Pressure

Inputted in the formula,

PG = 125.4 - 99.8

PG = 25.6 kPa

The gauge pressure inside the container is 25.6kPa which is option C.

4 0

3 years ago

The percent of remaining parent isotope in a radioactive decay process is 40 percent. How many half-lives have elapsed since the

muminat

Answer: Between 1 and 2.

Explanation:

Half life is the amount of time taken by a radioactive material to decay to half of its original value.

$a=\frac{a_o}{2^n}$ ............(1)

where,

a = amount of reactant left after n-half lives = 40

$a_o$ = Initial amount of the reactant = 100

n = number of half lives

Putting in the values we get:

$40=\frac{100}{2^n}$

$2^n=2.5$

taking log on both sides

$nlog(2)=log(2.5)$

$n=1.32$

Thus half-lives that have elapsed is between 1 and 2

7 0

3 years ago