Calculate the amount of heat needed to convert 50.0 g of liquid water at to steam at 100ºC.
16,700 J

113,000 J

104 J

209 J

Answer:J.K^-1. kg^-1

Explanation:

Heat capacity= H

Mass=m

Specific heat capacity= c

H=mc

J.K^-1 = c ×kg

c= J.K^-1/kg

=J.K^-1.kg^-1

Answer:

Solution A has the higher percent ionization and the higher pH.

Explanation:

Percent ionization depends on the concentration of acid in a solution. If the solution having more concentration of acid so the percent ionization will be lower while if the solution have low amount of acid i. e. dilute solution so the percent ionization will be higher. In solution A, the concentration of HNO2 is lower which is an acid so the percent ionization is higher and the pH of the solution is also higher as compared to solution B.

Answer:

Solution A has the higher percent ionization and the higher pH

Explanation:

Answer:

Ice and water on the ground affect incoming solar radiation by reflecting 4 percent of solar radiation that reaches the surface.

Explanation:

Answer:

ice and water on the ground affect incoming solar radiation by reflecting 4 percent of solar radiation that reaches the surface. the state of water and the sun angle are vital in determining the amount of reflection that take place. at low sun angle and at times when the surface is ice, more reflection occurs.

Explanation:

None

Answer:

S = 0.00014 moles /L = 1.4 * 10^-4 moles/L

Explanation:

Step 1: Data given

Temperature = 25.0 °C

Ksp = 1.1 * 10^-11

Step 2: The balanced equation

Mg(OH)2(s) ⇆ Mg^2+(aq) + 2OH-(aq)

Step 3: Define Ksp

[Mg(OH)2 = 1.11 * 10^-11 = S

[Mg^2+] = S

[OH-] = 2S

Ksp = [Mg^2+]*[OH-]²

Ksp = S * (2S)²

1.1 * 10^-11 = 4S³

S³ = 2.75 * 10^-12

S = 0.00014 moles /L

Answer:

28.58 g of NaOH

Explanation:

The question is incomplete. The missing part is:

"Calculate the mass of sodium hydroxide that the chemist must weigh out in the second step"

To do this, we need to know how much of the base we have to weight to prepare this solution.

First we know that is a sodium hydroxide aqueous solution so, this will dissociate in the ions:

NaOH -------> Na⁺ + OH⁻

As NaOH is a strong base, it will dissociate completely in solution, so, starting with the pH we need to calculate the concentration of OH⁻.

This can be done with the following expression:

14 = pH + pOH

and pOH = -log[OH⁻]

So all we have to do is solve for pOH and then, [OH⁻]. To get the pOH:

pOH = 14 - 13.9 = 0.10

[OH⁻] = 10⁽⁻⁰°¹⁰⁾

[OH⁻] = 0.794 M

Now that we have the concentration, let's calculate the moles that needs to be in the 900 mL:

n = M * V

n = 0.794 * 0.9

n = 0.7146 moles

Finally, to get the mass that need to be weighted, we need to molecular mass of NaOH which is 39.997 g/mol so the mass:

m = 39.997 * 0.7146

Answer:

5:22 am

Explanation:

The gas X decays following a first-order reaction.

The half-life ([tex]t_{1/2}[/tex]) is 25 min. We can find the rate constant (k) using the following expression.

[tex]k = \frac{ln2}{t_{1/2}} =\frac{ln2}{25min} = 0.028 min^{-1}[/tex]

We can find the concentration of X at a certain time ([tex][X][/tex]) using the following expression.

[tex][X] = [X]_0 \times e^{-k \times t}[/tex]

where,

[tex][X]_0[/tex]: initial concentration of X

t: time elapsed

[tex]\frac{[X]}{[X]_0}= e^{-k \times t}\\\frac{1/10[X]_0}{[X]_0}= e^{-0.028min^{-1} \times t}\\t=82min[/tex]

The earliest time Professor Utonium can come back to do experiments in the lab is:

4:00 + 82 = 5:22 am

Final answer:

The earliest Professor Utonium can return to the lab after a radioactive release is approximately 5:15 am, based on the half-life of 25 minutes and the requirement for the concentration of the gas to drop by a factor of 10, corresponding to just over 3 half-lives.

Explanation:

The question asks for the earliest time Professor Utonium can return to the lab after a release of a radioactive gas, X, which has a half-life of 25 minutes, and the lab is considered safe when its concentration drops by a factor of 10. Understanding that the decay of the radioactive element follows first-order kinetics, we can calculate the time required for the concentration to drop by this factor.

First-order decay implies that the time it takes for a substance to decay to half its initial amount is constant, known as the half-life. To reduce the concentration of a substance by a factor of 10, we need to go through a certain number of half-lives. The formula for calculating the amount of substance remaining after a given time is N = N0,[tex](1/2)^{(t/t1/2)}[/tex] where N is the remaining amount, N0 is the initial amount, t is time, and t1/2 is the half-life.

To reduce the concentration by a factor of 10, we effectively need the substance to go through just over 3 half-lives (since (1/2)³ = 1/8, which is just a bit more than one-tenth). Therefore, the calculation is 3 * 25 = 75 minutes after the initial release. Since the accident happened at around 4:00 am, adding 75 minutes means the earliest Professor Utonium can return to the lab is approximately 5:15 am.

Answer:

a) Balanced Overall Stoichiometric Equation

CHCl₃(g) + Cl₂(g) → CCl₄(g) + HCl(g)

b) The reaction intermediates include Cl(g) and CCl₃(g)

c) The rate of reaction of the rate determining step is:

Rate = k [CHCl₃] [Cl]

d) The rate of overall reaction is given as

Rate = K [CHCl₃] √[Cl₂]

e) The reaction rate increases by a multiple of 2√2 when the reactants' concentrations are doubled.

Explanation:

Step 1: Cl₂(g) → 2Cl(g) fast

Step 2: CHCl₃(g) + Cl(g) → CCl₃(g) + HCl(g) slow

Step 3: CCl₃(g) + Cl(g) → CCl₄(g) fast

a) The overall reaction is a reaction between Chloroform (CHCl₃) and Chlorine (Cl₂). It can be obtained by summing all the elementary equations and eliminating the reaction intermediates (the species that appear on both sides upon summing up all the elementary equations).

Cl₂(g) + CHCl₃(g) + Cl(g) + CCl₃(g) + Cl(g) → 2Cl(g) + CCl₃(g) + HCl(g) + CCl₄(g)

Now, eliminating the reaction intermediates (the species that appear on both sides upon summing up all the elementary equations), we are left with

Cl₂(g) + CHCl₃(g) → HCl(g) + CCl₄(g)

CHCl₃(g) + Cl₂(g) → CCl₄(g) + HCl(g)

b) Like I mentioned in (a), the reaction intermediates are the species that appear on both sides upon summing up all the elementary equations. They include:

Cl(g) and CCl₃(g)

c) The rate determining step is usually the slowest step among the elementary equations.

The rate of reaction expression is usually written from the slowest step.

The slowest step is step 2.

CHCl₃(g) + Cl(g) → CCl₃(g) + HCl(g) slow

The rate of reaction is then given as

Rate = k [CHCl₃] [Cl]

d) The rate of reaction for the overall reaction is obtained by substituting for any intermediates that appear in the rate of reaction for the rate determining step

The rate of reaction of the rate determining step is:

Rate = k [CHCl₃] [Cl]

But we can substitute for [Cl] by obtaining an expression for it from the step 1.

Step 1: Cl₂(g) → 2Cl(g)

K₁ = [Cl]²/[Cl₂]

[Cl]² = K₁ [Cl₂]

[Cl] = √{K₁ [Cl₂]}

We then substitute this into the rate determining step

Rate = k [CHCl₃] [Cl]

Rate = k [CHCl₃] √{K₁ [Cl₂]}

Rate = (k)(√K₁) [CHCl₃] √[Cl₂]

Let (k)(√K₁) = K (the overall rate constant)

Rate = K [CHCl₃] √[Cl₂]

e) If the concentrations of the reactants are doubled, by what ratio does the reaction rate change

Old Rate = K [CHCl₃] √[Cl₂]

If the concentrations of the reactants are doubled, the new rate would be

New Rate = K × 2[CHCl₃] × √{2 × [Cl₂]}

New Rate = K × 2[CHCl₃] × √2 × √[Cl₂]

New Rate = 2√2 K [CHCl₃] √[Cl₂]

Old Rate = K [CHCl₃] √[Cl₂]

New Rate = 2√2 × (Old Rate)

The reaction rate increases by a multiple of 2√2 when the reactants' concentrations are doubled.

Hope this Helps!!!!

Answer:

All of the choices.

Explanation:

As the reaction is involving with a mixture of H₂O and CH₃OH, these two reagents can work as nucleophyle of the reaction. Both of them, are polar and promoves a Sn1/E1 reaction. When it reacts with water it will produce product B); it will form product C) when it reacts with methanol, and product A) will be formed when the reaction undergoes an E1 reaction.

In this case, the only way to show you this, it's doing the mechanism of reaction for each product. Picture attached show the mechanism for the formation of all these products.

Treating (CH3)3C-Cl with H2O and CH3OH usually results in the formation of tert-butyl alcohol, (CH3)3COH, through a nucleophilic substitution reaction, making option B the correct answer.

Treating (CH3)3C-Cl with a mixture of H2O and CH3OH at room temperature typically involves a nucleophilic substitution reaction where the chloride ion (Cl-) is replaced by the nucleophile. In this case, the nucleophiles are water (H2O) and methanol (CH3OH). The product of this reaction would be (CH3)3COH, also known as tert-butyl alcohol, as both water and methanol could act as nucleophiles to perform the substitution, but water is generally a better nucleophile than methanol. Hence, option B is the correct answer.

To calculate the starting concentration of ADP in micromolar, use the equilibrium constant and the concentrations of ATP, creatine, and creatine phosphate at the start.

To calculate the starting concentration of ADP in micromolar, we need to use the equilibrium constant and the concentrations of ATP, creatine, and creatine phosphate at the start. The equation for the creatine kinase reaction is:

ATP + Creatine → ADP + Creatine Phosphate

Given that the standard free energy change (ΔG°) is -12.6 kJ/mol and the ΔG is -0.1 kJ/mol, we can calculate the equilibrium constant (K) using the equation: ΔG = -RT ln K.

Using the given values, we can substitute them into the equation to solve for K and then use the concentrations of ATP, creatine, and creatine phosphate to calculate the starting concentration of ADP in micromolar.

https://brainly.com/question/28590870

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Using the values given the ADP concentration came as approximately 527.12 μM.

To find the starting concentration of ADP in micromolar, we can use the Gibbs free energy equation:

ΔG = ΔG° + RT ln(Q)

where ΔG is the Gibbs free energy change under cellular conditions, ΔG° is the standard Gibbs free energy change, R is the universal gas constant (8.314 J/mol·K), T is the temperature in Kelvin, and Q is the reaction quotient.

The creatine kinase reaction is:

Creatine + ATP <=> Creatine phosphate + ADP

Given:

We need to find [ADP]. First, rearrange the Gibbs free energy equation to solve for Q:

ΔG - ΔG°' = RT ln(Q)

Q = e^{(ΔG - ΔG°') / RT}

Substitute the known values (assuming T = 298 K):

Q = e^{(-100 - (-12600)) / (8.314 × 298)}

Q = e^{12500 / 2479.87}

Q = e^{5.04} ≈ 155.50

Substitute Q into the reaction quotient expression:

Q = [Creatine phosphate] [ADP] / [Creatine][ATP]

155.50 = (2.5 × 10⁻²) [ADP] / ((1.7 × 10⁻²) (5 × 10⁻³))

155.50 = (2.5 × 10⁻²) [ADP] / (8.5 × 10⁻⁵)

155.50 = (2.5 / 8.5) × 10³ [ADP]

155.50 = 0.295 [ADP] × 10³

ADP ≈ 155.50 / 0.295 ≈ 527.12 μM

The starting concentration of ADP is approximately 527.12 μM.

Answer:

2.22 m

Explanation:

Step 1:

Data obtained from the question:

Frequency = (A + 88.3) MHz

We assume that the student ID is 20245347 as given in the question.

Therefore, A = 47 (last two digit of the 8-digit student ID)

Frequency = (47 + 88.3) MHz

Frequency = 135.3 MHz = 135.3x10^6 Hz

Wavelength =?

Recall:

Velocity of electromagnetic wave is 3x10^8 m/s2

Step 2:

Determination of the wavelength of the radio wave. This is illustrated below:

Velocity = wavelength x frequency

Wavelength = Velocity /frequency

Wavelength = 3x10^8 / 135.3x10^6

Wavelength = 2.22 m

Answer:

1. Partial pressure of N2 is 204.5 mmHg

2. Partial pressure of Cl2 is 613.5 mmHg

Explanation:

Step 1:

The equation for the reaction. This is given below:

NCl3 —> N2 (g) + Cl2 (g)

Step 2:

Balancing the equation.

NCl3 (l) —> N2 (g) + Cl2 (g)

The above equation is balanced as follow:

There are 2 atoms of N on the right side and 1 atom on the left side. It can be balance by putting 2 in front of NCl3 as shown below:

2NCl3 (l) —> N2 (g) + Cl2 (g)

There are 6 atoms of Cl on the left side and 2 atoms on the right side. It can be balance by putting 3 in front of Cl2 as shown below:

2NCl3 (l) —> N2 (g) + 3Cl2 (g)

Now the equation is balanced.

Step 2:

Determination of the mole fraction of each gas.

From the balanced equation above, the resulting mixture of the gas contains:

Mole of N2 = 1

Mole of Cl2 = 3

Total mole = 4

Therefore, the mole fraction for each gas is:

Mole fraction of N2 = mole of N2/total mole

Mole fraction of N2 = 1/4

Mole fraction of Cl2 = mole of Cl2/total mole

Mole fraction of Cl2 = 3/4

Step 3:

Determination of the partial pressure of N2.

Partial pressure = mole fraction x total pressure

Total pressure = 818 mmHg

Mole fraction of N2 = 1/4

Partial pressure of N2 = 1/4 x 818

Partial pressure of N2 = 204.5 mmHg

Step 4:

Determination of the partial pressure of Cl2.

Partial pressure = mole fraction x total pressure

Total pressure = 818 mmHg

Mole fraction of Cl2 = 3/4

Partial pressure of Cl2 = 3/4 x 818

Partial pressure of Cl2 = 613.5 mmHg

Answer:

[tex]p_{N_2}=204.5mmHg\\p_{Cl_2}=613.5mmHg[/tex]

Explanation:

Hello,

In this case, the undergoing chemical reaction is:

[tex]2NCl_3(g)\rightarrow N_2(g)+3Cl_2(g)[/tex]

Thus, by knowing that the nitrogen trichloride is completely decomposed, one assumes there is one mole of nitrogen and three moles of chlorine (stoichiometric coefficients) as a basis to compute the partial pressures since they have the mole ratio from the nitrogen trichloride. Hence, the mole fractions result:

[tex]x_{N_2}=\frac{1}{1+3}=0.25\\ x_{Cl_2}=1-0.25=0.75[/tex]

In such a way, for the final pressure 818 mmHg, the partial pressures become:

[tex]p_{N_2}=x_{N_2}p_T=0.25*818mmHg=204.5mmHg\\p_{Cl_2}=x_{Cl_2}p_T=0.75*818mmHg=613.5mmHg[/tex]

Best regards.

Answer:

-- 5.8×10⁻⁹ of the H is in 2P states at T=5900 K, a typical Sun surface temperature.

-- 3.3×10⁻¹² of the H is in 2P states at T=4300 K, a typical Sunspot temperature.

Explanation:

Answer:

Explanation:

your question seems to be  uncompleted , but however i have a solution to a similar question, check the attachment and follow the format to evaluate your question.

check the attachement

Question:

Which of the following statements is TRUE?

A. Perpetual motion machines are a possibility in the near future.

B. The entropy of a system always decreases for a spontaneous process.

C. A spontaneous reaction is always a fast reaction.

D. There is a "heat tax" for every energy transaction.

E. None of the above are true.

Answer:

The correct answer is D)

There is a "heat tax" for every energy transaction.

Explanation:

Heat and work are two different ways in which energy is moved from one device to another. In the field of thermodynamics the distinction between Heat and Work is significant. The transfer of thermal energy between systems is heat. This is what is referred to as "heat tax".

No other statement in the question above is correct.

Cheers!

Answer: the effects of cholera toxin on cAMP in the intestinal cells is that it INCREASES cAMP production.

Explanation:

Vibrio cholerae is a gram negative bacterium which produces a protein cholera toxin that is responsible for the characteristic symptoms of cholera such as

watery diarrhea, vomiting, rapid heart rate, loss of skin elasticity, low blood pressure, thirst, and muscle cramps. There is need for body fluids and Na replacement to avoid severe dehydration results which may lead to death.

Cyclic adenosine monophosphate( cAMP) is a derivative used for intracellular signal transduction in organisms. The cholera toxin produced by the bacteria INCREASES the production of cAMP through its polypeptides( which consist of active protomer and binding protomer). The cholera toxin first binds to cell surface receptors, the protomer then enters the cell and bind with and activate the adenylate cyclase. Increasing adenylate cyclase activity will INCREASE cellular levels of cAMP, increasing the activity of ion pumps that remove ions from the cell. Due to osmotic pressure changes, water also must flow with the ions into the lumen of the intestinal mucosa, dehydrating the tissue. I hope this helps, thanks.

Answer:

Explanation:

Hydroponics is the process of growing crops using only water and liquid fertilizer. This process is great when your in the big city.

Hydroponics is a method of growing plants in a nutrient-rich water solution rather than soil, which allows precise control of nutrients and is used in research and commercial greenhouses for robust crop production.

Hydroponics is a highly efficient farming technique where plants are grown in a water-nutrient solution, rather than in soil. This method allows for precise control over the nutritional environment of the plants, which is why it is favored in scientific research for studying plant nutrient deficiencies and for producing robust, healthy crops.

In hydroponic systems, the need for soil is eliminated, and plants are given the exact nutrients they require directly. Because of this, hydroponics is used not only in laboratories but also in commercial greenhouse environments to cultivate flowers, vegetables, and other crops.

These crops are often resilient to pests and harsh conditions, contributing to sustainable food production and agricultural development.

Greenhouse management and hydroponics go hand in hand, as many plants grown hydroponically are also cultivated under controlled climates within greenhouses. The elimination of soil in hydroponics also helps mitigate the ecological, economic, and health concerns associated with excessive pesticide use in traditional agriculture.

Answer:

3.71%

Explanation:

The phenolphthalein endpoint refers to the reactions:

OH⁻ + H⁺ → H₂O

CO₃⁻² + H⁺ → HCO₃⁻

While the methyl orange endpoint to:

HCO₃⁻ + H⁺ → H₂CO₃

So the additional volume required for the second endpoint tells us the amount of HCO₃⁻ species, which in turn is the total amount of Na₂CO₃ in the sample:

0.700 mL * 0.100 M * [tex]\frac{1mmolHCO_{3}^{-}}{1mmolHCl}[/tex] = 0.07 mmol HCO₃⁻

Now we calculate the mass of Na₂CO₃, using its molecular weight:

0.07 mmol HCO₃⁻ = 0.07 mmol Na₂CO₃

0.07 mmol Na₂CO₃ * 106 mg/mmol = 7.42 mg Na₂CO₃

No calculations using the volume of the first equivalence point are required because the problem already tells us the mass of the sample is 0.200 g.

0.200 g ⇒ 0.200 * 1000 = 200 mg

%Na₂CO₃ = 7.42 mg/200 mg * 100 = 3.71%

Answer:

[tex]Kc=6.875x10^{-3}[/tex]

Explanation:

Hello,

In this case, for the given chemical reaction at equilibrium:

[tex]2 SO_3 ( g ) \rightleftharpoons 2 SO_ 2 ( g ) + O_ 2 ( g )[/tex]

The initial concentration of sulfur trioxide is:

[tex][SO_3]_0=\frac{0.660mol}{4.00L}=0.165M[/tex]

Hence, the law of mass action to compute Kc results:

[tex]Kc=\frac{[SO_2]^2[O_2]}{[SO_3]^2}[/tex]

In such a way, in terms of the change [tex]x[/tex] due to the reaction extent, by using the ICE method, it is modified as:

[tex]Kc=\frac{(2x)^2*x}{(0.165-2x)^2}[/tex]

In that case, as at equilibrium 0.11 moles of oxygen are present, [tex]x[/tex] equals:

[tex]x=[O_2]=\frac{0.110mol}{4.00L}=0.0275M[/tex]

Therefore, the equilibrium constant finally turns out:

[tex]Kc=\frac{(2*0.0275)^2*0.0275}{(0.165-2*0.0275)^2} \\\\Kc=6.875x10^{-3}[/tex]

Best regards.

Answer:

pH= 13.03

Explanation:

Since dissociation of Sr(OH)2= Sr2+ + 2[OH-]

[OH-]=2×0.0538 = 0.1076M

pOH= -log[0.1076]= 0.97

pH= 14-pOH = 14-0.97= 13.03

Answer:

Explanation:

Check below for the answer in the attachment.

To solve this problem, we can use the ideal gas law equation PV=nRT. We can find the number of moles in the first balloon using the given information, and then use that value to find the volume of the second balloon.

To solve this problem, we can use the ideal gas law, which states that PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature in Kelvin.

First, we can use the given information to find the number of moles in the first balloon. Rearranging the ideal gas law equation, we have n = PV / RT. Plugging in the values, we get n = (5.2 mol)(23.5 L) / (0.0821 atm L/mol K)(T in Kelvin).

Once we have the number of moles for the first balloon, we can use this value to find the volume of the second balloon. Rearranging the ideal gas law equation, we have V = nRT / P. Plugging in the values and solving for V, we get V = (5.2 mol)(0.0821 atm L/mol K)(T in Kelvin) / (P)

Answer:

27.60 g urea

Explanation:

The freezing-point depression is expressed by the formula:

In this case,

m is the molality of the urea solution in X (mol urea/kg of X)

First we calculate the molality:

Now we calculate the moles of urea that were dissolved:

550 g X ⇒ 550 / 1000 = 0.550 kg X

Finally we calculate the mass of urea, using its molecular weight:

The initial pH of 0.100 M HNO2 is approximately 2.17. It takes 20.0 mL of 0.200 M KOH to reach the equivalence point. The subsequent pH values at various points in the titration reflect the changing concentrations of HNO2 and OH-.

A 40.0-mL sample of 0.100 M HNO2 (Ka = 4.6 x 10-4) is titrated with 0.200 M KOH.

a. The pH when no base is added

To find the initial pH, we first need to calculate the concentration of H3O+ using the equilibrium expression for the weak acid:

HNO2 ⇌ H+ + NO2-

Using Ka, we get:

Ka = [H+][NO2-] / [HNO2]

4.6 x 10-4 = x2 / 0.100

Solving for x, we get:

x = √(4.6 x 10-4 * 0.100) = 0.00678 M

pH = -log(0.00678) ≈ 2.17

b. The volume of KOH required to reach the equivalence point

The moles of HNO2 are:

0.040 L * 0.100 M = 0.004 mol

Since KOH and HNO2 react in a 1:1 molar ratio, the volume of 0.200 M KOH required is:

0.004 mol / 0.200 M = 0.020 L = 20.0 mL

c. The pH after adding 5.00 mL of KOH

Moles of KOH added:

0.005 L * 0.200 M = 0.001 mol

Moles of HNO2 remaining:

0.004 mol - 0.001 mol = 0.003 mol

Concentration of HNO2 remaining = 0.003 mol/0.045 L = 0.0667 M

Concentration of NO2- formed = 0.001 mol/0.045 L = 0.0222 M

Using the Henderson-Hasselbalch equation:

pH = pKa + log([A-]/[HA])

pH = -log(4.6 x 10-4) + log(0.0222/0.0667) ≈ 3.35

d. The pH at one-half the equivalence point

At one-half the equivalence point, the concentration of [A-] = [HA], so:

pH = pKa = -log(4.6 x 10-4) ≈ 3.34

e. The pH at the equivalence point

At the equivalence point, all HNO2 has been converted to NO2-:

NO2- will hydrolyze to produce OH-:

NO2- + H2O ⇌ HNO2 + OH-

Using Kb for NO2-:

Kb = Kw/Ka = 1.0 x 10-14 / 4.6 x 10-4 = 2.17 x 10-11

Setting up the equation:

Kb = [OH-][HNO2] / [NO2-]

2.17 x 10-11 = x2 / 0.100

Solving for x:

x = √(2.17 x 10-11 * 0.100) = 1.47 x 10-6

pOH = -log(1.47 x 10-6) ≈ 5.83

pH = 14 - 5.83 = 8.17

f. The pH after 30 mL of the base is added

Moles of KOH added:

0.030 L * 0.200 M = 0.006 mol

Excess moles of OH-:

0.006 mol - 0.004 mol = 0.002 mol

Concentration of OH- in the total volume:

0.002 mol / 0.070 L = 0.02857 M

pOH = -log(0.02857) ≈ 1.54

pH = 14 - 1.54 = 12.46

The correct answers are: (a). [H⁺] = 2.17; (b). [tex]\text{Volume} = 20.0\ mL[/tex]; (c). [tex][NO_2^-] = \text{0.0222 M}[/tex]; (d). pH = 3.34; (e). [tex]\text{pH} = 8.02[/tex]; (f). pH = 12.46.

Let's solve the different parts of the titration problem step-by-step:

a. pH when no base is added:

First, we need to find the pH of a 0.100 M HNO₂ solution. HNO₂ is a weak acid and it partially ionizes in water:

The expression for the acid dissociation constant Ka is:

Assuming that the initial concentration of HNO₂ is C0 = 0.100 M and the change in concentration is x:

Assuming x is small relative to 0.100 M:

b. Volume of KOH required to reach the equivalence point:

c. pH after adding 5.00 mL of KOH:

Using the Henderson-Hasselbalch equation:

d. pH at one-half the equivalence point:

At one-half the equivalence point, [HNO₂] = [NO₂⁻], so pH = pKa.

e. pH at the equivalence point:

At the equivalence point, all HNO₂ has reacted to form NO₂⁻. The solution contains NO₂⁻ ions, which hydrolyze:

Let x be the concentration of OH⁻:

f. pH after 30 mL of the base is added:

Answer:

1) 16 mL of toluene is necessary to recrystallize 3.2 g of compound A

2) 2.4 g of A is the maximum amount that could be recovered.

3) 1.6 g of compound A  can be recovered if you accidentally use twice as much  toluene as was necessary

Explanation:

1)

The volume of the solvent ( toluene) = [tex]\frac{starting \ amount }{solubility \ at \boiling \ point }[/tex]

= [tex]\frac{3.2 \ g}{0.2 \ g/mL}[/tex]

= 16 mL

∴  16 mL of toluene is necessary to recrystallize 3.2 g of compound A

2)

The maximum amount    A that could be recovered if the saturated solution was allowed to cool to 0 ºC is determined by the difference of the starting amount and amount left in the solution at 0 ºC

i.e

maximum amount of A = 3.2 - ( 16 mL × 0.05 g/mL)

= 3.2 g - 0.8 g

= 2.4 g

∴  2.4 g of A is the maximum amount that could be recovered.

3)

Amount of A that would be  recovered, if you accidentally used twice as much toluene as was necessary is calculated as follows;

amount of A = 3.2g - (32 mL × 0.05 g/mL)

= 3.2 g - 1.6 g

= 1.6 g

Thus; 1.6 g of compound A  can be recovered if you accidentally use twice as much  toluene as was necessary

Answer:

The one that will begin to precipitate first will be the lead chromate (PbCrO₄)

Explanation:

First of all, let's determine the equations involved:

Pb(NO₃)₂ →   Pb²⁺  +   2NO₃⁻

0.001          0.001       0.002

Ba(NO₃)₂  →  Ba²⁺  +  2NO₃⁻

0.100          0.100      0.200  

Sodium chromate as a soluble salt, can be also dissociated in:

Na₂CrO₄ →  2Na⁺ +  CrO₄²⁻

As the chromate can react to both cations of the aqueous solution, there will be formed 2 precipitates. When the saturation point is reached, which is determined by the Kps, everything that cannot be dissolved will precipitate.

The first to saturate the solution will precipitate first.

CrO₄²⁻ + Pb²⁺  ⇄  PbCrO₄

  s            s             s²  = Kps

 Kps = s² ⇒ [CrO₄²⁻] . [Pb²⁺] =  2.80×10⁻¹³

[CrO₄²⁻] . 0.001 = 2.80×10⁻¹³

[CrO₄²⁻] = 2.80×10⁻¹³ / 0.001 = 2.80×10⁻¹⁰

This is the concentration for the chromate when the lead chromate starts to precpitate.

CrO₄²⁻ + Ba²⁺  ⇄  BaCrO₄

  s            s             s²  = Kps  

Kps = [CrO₄²⁻] . [Ba²⁺]

1.17×10⁻¹⁰ = [CrO₄²⁻] . 0.100

[CrO₄²⁻] = 1.17×10⁻¹⁰ / 0.100 =  1.17×10⁻⁹

The first one that precipitates needs less chromate ion to start precipitating, in conclusion the one that will begin to precipitate first will be lead chromate.

The solid that will precipitate first is PbCrO₄.

To determine which solid will precipitate first, we need to compare the solubility product constants [tex](\( K_{\text{sp}} \))[/tex] for each possible precipitate. The compound with the lower [tex]\( K_{\text{sp}} \)[/tex] will precipitate first because it has lower solubility in water.

The solubility products given are:

- [tex]\( K_{\text{sp}} \) of BaCrO\(_4\) = \( 1.17 \times 10^{-10} \)[/tex]

- [tex]\( K_{\text{sp}} \) of PbCrO\(_4\) = \( 2.80 \times 10^{-13} \)[/tex]

We need to find the concentration of [tex]\(\text{CrO}_4^{2-}\) (\([ \text{CrO}_4^{2-} ]\))[/tex] at which each compound will begin to precipitate.

Calculation for BaCrO₄:

The reaction for the precipitation of BaCrO₄ is:

[tex]\[ \text{Ba}^{2+} (aq) + \text{CrO}_4^{2-} (aq) \rightarrow \text{BaCrO}_4 (s) \][/tex]

The [tex]\( K_{\text{sp}} \)[/tex] expression is:

[tex]\[ K_{\text{sp}} = [\text{Ba}^{2+}] [\text{CrO}_4^{2-}] \][/tex]

Given:

[tex]\[ K_{\text{sp}} (\text{BaCrO}_4) = 1.17 \times 10^{-10} \][/tex]

[tex]\[ [\text{Ba}^{2+}] = 0.100 \, \text{M} \][/tex]

We can solve for [tex]\([ \text{CrO}_4^{2-} ]\)[/tex]:

[tex]\[ 1.17 \times 10^{-10} = (0.100) [\text{CrO}_4^{2-}] \][/tex]

[tex]\[ [\text{CrO}_4^{2-}] = \frac{1.17 \times 10^{-10}}{0.100} \][/tex]

[tex]\[ [\text{CrO}_4^{2-}] = 1.17 \times 10^{-9} \, \text{M} \][/tex]

Calculation for PbCrO₄:

The reaction for the precipitation of PbCrO₄ is:

[tex]\[ \text{Pb}^{2+} (aq) + \text{CrO}_4^{2-} (aq) \rightarrow \text{PbCrO}_4 (s) \][/tex]

The [tex]\( K_{\text{sp}} \)[/tex] expression is:

[tex]\[ K_{\text{sp}} = [\text{Pb}^{2+}] [\text{CrO}_4^{2-}] \][/tex]

Given:

[tex]\[ K_{\text{sp}} (\text{PbCrO}_4) = 2.80 \times 10^{-13} \][/tex]

[tex]\[ [\text{Pb}^{2+}] = 0.001 \, \text{M} \][/tex]

We can solve for [tex]\([ \text{CrO}_4^{2-} ]\)[/tex]:

[tex]\[ 2.80 \times 10^{-13} = (0.001) [\text{CrO}_4^{2-}] \][/tex]

[tex]\[ [\text{CrO}_4^{2-}] = \frac{2.80 \times 10^{-13}}{0.001} \][/tex]

[tex]\[ [\text{CrO}_4^{2-}] = 2.80 \times 10^{-10} \, \text{M} \][/tex]

Comparison:

- The concentration of [tex]\(\text{CrO}_4^{2-}\)[/tex] needed to precipitate BaCrO₄ is [tex]\( 1.17 \times 10^{-9} \, \text{M} \)[/tex].

- The concentration of [tex]\(\text{CrO}_4^{2-}\)[/tex] needed to precipitate PbCrO₄ is [tex]\( 2.80 \times 10^{-10} \, \text{M} \)[/tex].

Since [tex]\( 2.80 \times 10^{-10} \, \text{M} \)[/tex] is smaller than[tex]\( 1.17 \times 10^{-9} \, \text{M} \), PbCrO\(_4\)[/tex] will precipitate first.

Answer:

Explanation:

Using Dalton's law of partial pressure

P total pressure = Pressure of helium + Pressure of neon + Vapor pressure of water

P = 28.3 mmHg, Pressure of helium = 381 mmHg, Vapor pressure of water at 28°C

791 mmHg - 381 mmHg - 28.3 mmHg = Pressure of neon

Pressure of neon = 381.7 mmHg

Answer:

A. Kinetic energies of molecules increase.

B. Speeds of molecules increase.

C. Number of collisions per second increase.

Final answer:

Pressure changes according to Le Chatelier's principle and can be influenced by mechanical and thermal mechanisms, as well as by the kinetic activity of gas molecules.

Explanation:

Pressure changes can be understood in terms of Le Chatelier's principle, which states that when a change is imposed on a system at equilibrium, the system adjusts to counteract that change.

In the case of gases, increasing the pressure (by decreasing volume) leads to a shift in the equilibrium to reduce the number of gas particles, if possible, thereby reducing the pressure. Conversely, decreasing the pressure (by increasing volume) would have the opposite effect.

Pressure also varies due to thermal and mechanical mechanisms. Heating air causes it to rise and reduce surface air pressure, while cooling air causes it to descend, increasing pressure.

Mechanical changes occur when airflow is blocked, causing a build-up of air and increased pressure. Additionally, the kinetic theory of gases suggests that gases exert pressure because of the continuous motion of their particles, colliding with container walls and exerting force.

Furthermore, variations in pressure at different points of a fluid are important for driving the phenomena of buoyancy, as well as affecting divers and airplane passengers through changes in ambient pressure.

Answer:

mass of U-235  = 15.9 g (3 sig. figures)

Explanation:

1 atom can produce -------------------------> 3.20 x 10^-11 J energy

x atoms can produce ----------------------> 1.30 x 10^12 J energy

x = 1.30 x 10^12 / 3.20 x 10^-11

x = 4.06 x 10^22 atoms

1 mol ----------------------> 6.023 x 10^23 atoms

y mol ----------------------> 4.06 x 10^22 atoms

y = 0.0675 moles

mass of U-235 = 0.0675 x 235 = 15.8625

mass of U-235  = 15.9 g (3 sig. figures)

Answer:

1.52V

Explanation:

Oxidation half equation:

2Al(s)−→2Al^3+(aq) + 6e

Reduction half equation

3Sn2^+(aq) + 6e−→3Sn(s)

E°cell= E°cathode - E°anode

E°cathode= −0.140 V

E°anode= −1.66 V

E°cell=-0.140-(-1.66)

E°cell= 1.52V

Final answer:

The overall cell potential for the redox reaction between tin and aluminum in a galvanic cell is calculated as +1.52 V, indicating a spontaneous reaction with tin being oxidized at the anode and aluminum reduced at the cathode.

Explanation:

To calculate the standard cell potential for a redox reaction involving tin (Sn) and aluminum (Al), we apply the reduction potentials of their respective half-reactions. The half-reaction for tin is as follows: Sn(s) ightarrow Sn2+(aq) + 2 e - , with an associated standard reduction potential (E & Ocirc ;) of - 0.140 V, however, its oxidation potential is actually +0.140 V.

For aluminum, the half-reaction is: Al3+(aq) + 3 e - ightarrow Al(s), with an E & Ocirc ; of - 1.66 V. In a galvanic cell, the aluminum will oxidize, and since it’s a reduction potential, for oxidation, we take the negative of this value, which would make it +1.66 V.

To find the overall cell potential, we use the equation Ecell = Ecathode - Eanode. In this reaction, Sn(s) is our anode, and Al(s) is our cathode. However, since aluminum's E & Ocirc ; is already negative (signifying oxidation), we reverse its sign for use in the cell potential equation.

Ecell = Ecathode - Eanode = (+1.66 V) - (+0.14 V) = +1.66 V - 0.14 V = +1.52 V

The standard cell potential is positive, indicating that the redox reaction is spontaneous. Tin is oxidized at the anode, and aluminum is reduced at the cathode, forming the basis for electric current flow in the cell.

Metals are good conductors of electricity due to the mobile valence electrons which can move freely within the metallic crystal lattice, facilitating electric charge transfer.

Metals are good conductors of electricity because they contain mobile valence electrons. In metallic bonds, these valence electrons are not associated with a particular atom or pair of atoms, but move freely within the crystal lattice of positively charged metal ions. They form what is often referred to as an 'electron sea'. These free moving electrons can carry charge from one place to another when a voltage (electric potential difference) is applied, making metals good conductors of electricity.

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