CHEMISTRY COLLEGE

Hydrazine, N2H4, is a weak base and is used as fuel in the space shuttle.N2H4(aq)+H2O(l)âN2H5+(aq)+OHâ(aq)

Part A

If the pH of a 0.133 M solution is 10.66, what is the ionization constant of the base?

Express your answer using two significant figures.

Answers

Answer 1

Answer:

Answer:

Kb = 1.6*10^-6

Explanation:

The given reaction is:

$N2H4(aq)+H2O(l)\rightarrow N2H5+(aq)+OH-(aq)$

The ionization constant of the base Kb is given as:

$Kb = ([N2H5+][OH-])/([N2H4])------(1)$

The pH = 10.66

therefore, pOH = 14-pH = 14-10.66 =3.34

$[OH-] = 10^(-pOH) =10^(-3.34) =4.57*10^(-4) M$

[N2H5+] = [OH-] = 4.57*10^-4M

[N2H4] = 0.133 M

Based on eq(1)

$Kb = ([4.57*10^(-4)]^(2))/([0.133])=1.6*10^(-6)$

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5. The partition coefficient of Compound A is 7.5 in dichloromethane (a.k.a. methylene chloride) with respect to water. a. If 5 grams of Compound A were dissolved in 100 mL of water, how much of Compound A would be extracted with four 25-mL portions of dichloromethane

Answers

Answer:

4.93g are extracted

Explanation:

Partition coefficient (P) is defined as the ratio of solute dissolved in the organic solvent and the solute dissolved in the aqueous phase.

That is:

P = 7.5 = Concentration in dichloromethane / Concentration in water.

Knowing this, in the first extraction with 25mL of dichloromethane you will extract:

7.5 = (X/25mL) / (5g - X) / 100mL

Where X is the amount of compound A that is extracted.

7.5 = 100X / (125 - 25X)

937.5 - 187.5X = 100X

937.5 = 287.5X

3.26g of A are extracted in the first extraction.

In water will remain 5g - 3.26g = 1.74g

In the second extraction you will extract:

7.5 = (X/25mL) / (1.74g - X) / 100mL

7.5 = 100X / (43.5 - 25X)

326.25 - 187.5X = 100X

326.25 = 287.5X

1.13g are extracted in the second extraction.

And remain: 1.74g - 1.13g = 0.61g

In the third extraction you will extract:

7.5 = (X/25mL) / (0.61g - X) / 100mL

7.5 = 100X / (15.25 - 25X)

114.375 - 187.5X = 100X

114.375 = 287.5X

0.40g are extracted in the third extraction.

And remain: 0.61g - 0.40g = 0.21g

In the second extraction you will extract:

7.5 = (X/25mL) / (0.21g - X) / 100mL

7.5 = 100X / (5.25 - 25X)

39.375 - 187.5X = 100X

39.375 = 287.5X

0.14g are extracted in the fourth extraction.

Thus, after the three extractions you will extract: 0.14g + 0.40g + 1.13g + 3.26g = 4.93g are extracted

Final answer:

The process involves using the partitioncoefficient to determine how much of Compound A will prefer the dichloromethane solvent over the water. Following a calculation process through four rounds of extraction, it is concluded that approximately 4.999g of Compound A will be extracted using four 25mL portions of dichloromethane.

Explanation:

The partition coefficient of a compound is a measure of how much it prefers one solvent over another. Given that the partition coefficient of Compound A is 7.5 in dichloromethane with respect to water, we can predict how much of this compound could be extracted using four separate 25 mL portions of dichloromethane.

Here's the step-by-step calculation process:

We start with 5 grams of Compound A in 100 mL of water. Given the partition coefficient, in the initial phase, 5/(7.5+1)=0.625g remains in water and 7.5/8.5*5=4.375g goes into the dichloromethane.
After one extraction with 25ml of dichloromethane, the amount left in the water will be 0.625g*1/(7.5+1)=0.069g.
After the second extraction: 0.069g*1/(7.5+1) = 0.008g.
After the third extraction: 0.008g*1/(7.5+1) = 0.0009g.
After the fourth extraction: 0.0009g*1/(7.5+1) = 0.0001g.

In total, around 4.999g of compound A will be extracted using four 25mL portions of dichloromethane.

Learn more about Partition Coefficient here:

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Find the density of an object that has a volume of 2.3 x 10^2 and a mass of
3.5 x 10^3. *

Answers

Answer:

$(250)/(23)$

Step-by-step explanation:

$10^(2) = 100$
2.3 × 100 = 230
$10^(3) = 1000$
3.5 × 1000 = 3500
$D = (m)/(v)$
$D = (3500)/(230)$
3500 ÷ 230 = $(250)/(23)$

I hope this helps!

Find the mass of oxygen in grams produced by the decomposition of 100.0 g of CO2

Answers

The balanced chemical equation is :

$2CO_2->2CO+O_2\n\n$

Moles of $CO_2$ ,

$n = (100\ g)/(44.01\ g/mol)\n\nn=2.27\ mol$

Now, by given chemical equation , we can see 2 mole of $CO_2$ react with 1 mole of $O_2$ .

So , 2.27 mole react with :

$N=(2.27)/(2)\ mol\n\nN=1.135\ mol$

Mass of oxygen is :

$M = N * 16\n\nM=1.135* 16\ g\n\nM =18.16\ g$

Therefore, mass of oxygen in grams produced is 18.16 g.

Hence, this is the required solution.

Which of the following do you need to know to be able to calculate the molarity of a salt solution ? I. the mass of salt added II. the molar mass of the salt III. the volume of water added IV. the total volume of the solution A) II and III only B) I, II, and IV only C) I, II, and III only D) I and III only E) You need all of the information.

Answers

According to molar concentration, for calculating molarity of salt solution mass,molar mass of salt and volume of solution is required , hence option B is correct.

What is molar concentration?

Molar concentration is defined as a measure by which concentration of chemical substances present in a solution are determined. It is defined in particular reference to solute concentration in a solution . Most commonly used unit for molar concentration is moles/liter.

The molar concentration depends on change in volume of the solution which is mainly due to thermal expansion. Molar concentration is calculated by the formula, molar concentration=mass/ molar mass ×1/volume of solution in liters.

In terms of moles, it's formula is given as molar concentration= number of moles /volume of solution in liters.

Learn more about molar concentration,here:

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Explanation:

to find molarity

1the mass of salt added

Find the number of moles of solute dissolved in solution,

2 molar mass of salt

Find the volume of solution in liters,

4 total volume of solution

so B

A solution of NaOH has a concentration of 25.00% by mass. What mass of NaOH is present in 0.250 g of this solution? Use the periodic table in the toolbar if needed.

Answers

Answer : The mass of NaOH present in the solution is, 0.0625 grams

Explanation : Given,

Mass % = 25 %

Mass of solution = 0.250 g

Formula used :

$Mass\%=\frac{\text{Mass of}NaOH}{\text{Mass of solution}}* 100$

Now put all the given values in this formula, we get the mass of NaOH.

$25=\frac{\text{Mass of}NaOH}{0.250g}* 100$

$\text{Mass of}NaOH=0.0625g$

Therefore, the mass of NaOH present in the solution is, 0.0625 grams

The concentration of NaOH is 25.00% by mass, it means that 25.00% of the mass of the solution is of NaOH. Hence:

$m_(NaOH)=25.00\%* m_(solution)\Longrightarrow m_(NaOH)=(25)/(100)* 0.250~g\iff\n\n\boxed{m_(NaOH)=0.0625~g}$

When a polar bond is formed between 2 atoms which atom receives a partial positive charge

Answers

Answer:

The less electronegative atom

Explanation:

Water contains polar bonds. Water is made up of oxygen and hydrogen. Oxygen is more electronegative then hydrogen so it is partial negative (because electron spend more time around oxygen in the polar bond), whereas, hydrogen has a partial positive charge as it is less electronegative (electrons spend less time around hydrogen in this polar bond).

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