A chemistry student weighs out of an unknown solid compound and adds it to of distilled water at . After minutes of stirring, only some of the has dissolved. The student drains off the solution, then washes, dries and weighs the that did not dissolve. It weighs 0.570 kg.

Required:
a. Using the information above, can you calculate the solubility of X?
b. If so, calculate it. Remember to use the correct significant digits and units. .

Answer:

-1648.4 kJ/mol

Explanation:

Based on Hess's law:

ΔHr = ∑n×ΔH°f(products) - ∑n×ΔH°f(reactants)

In the reaction:

4Fe(s) + 3O₂(g) → 2Fe₂O₃(s)

ΔHr = 2 ΔH°f {Fe₂O₃} - (4ΔH°f {Fe(s)} + 3ΔH°f{O₂(g)}

As:

ΔH°f {Fe₂O₃} = -824.2kJ/mol

ΔH°f {Fe(s)} = 0.0kJ/mol

ΔH°f{O₂(g)} = 0.0kJ/mol.

Thus,

ΔHr = 2 ₓ -824.2kJ/mol =

Answer:

-1648.4 kJ

Explanation:

The product has the only nonzero heat of formation, so it is the only value needed to calculate the enthalpy of this reaction. Normally, you would want to express the enthalpy of a reaction with respect to one mole of a chemical species, whether it is a reactant or product. However, since the balanced chemical equation contains only coefficients greater than 1, you should consider how the enthalpy relates to one mole of each substance according to the coefficients. In other words,  − 1648.4  kJ  of heat is released when 4  mol  of  Fe  reacts with 3  mol  of  O2  to produce 2  mol  of  Fe2O3 .

Answer: they blow up

Explanation: add them together and they will blow up

Answer:

Magnesium nitrate Reactions

Magnesium nitrate has a high affinity towards water. Therefore, heating it results to decompose into magnesium oxide, nitrogen oxides, and oxygen. 2 Mg(NO3)2 → 2 MgO + 4 NO2 + O2.

Answer:

pH = 9.08

Explanation:

Quinine, C₂₀H₂₄O₂N₂, Q, is a weak base that, in water, has as equilibrium:

Q + H₂O ⇄ QH⁺ + OH⁻

Where pKb is 5.10

Using H-H equation for weak bases:

pOH = pKb + log₁₀ [QH⁺] / [Q]

The reaction of quinine with HCl is:

Q + HCl → QH⁺ + Cl⁻

Initial moles of quinine are 0.125 moles and moles added of HCl are:

0.05000L × (1.00mol / L) = 0.05000moles.

That means after the addition of 50.00mL of the HCl solution, moles of Q and QH⁺ are:

Q = 0.125mol - 0.050mol = 0.075 moles

QH⁺ = 0.050 moles

Replacing in H-H equation:

pOH = 5.10 + log₁₀ [0.050] / [0.075]

pOH = 4.92

As pH = 14 - pOJ

Answer:

Osmium

Explanation:

If you take a look at the attached image of a periodic table below, you will see that the element in the 6th period and 8th group is Osmium. Hope this helps!

Answer:the volume of the gas particles is negligible compared with the total volume of the  gas.--D

Explanation:

According to the Kinetic Molecular Theory for ideal gases, it states that

--Gases are composed of larges  molecules which are in constant random motion  in a straight line

--The volume of the gas particles is negligible compared to the total volume in which the gas is contained.

-----The  Attractive and repulsive forces between gas molecules is insignificant ie There are no interactive forces.

----The collisions of the particles  are perfectly elastic and energyis  being transferred between the particles but the total energy remaining constant

From the  statements of the kinetic Molecular theory of ideal gases, it can be seen that the statement which describes the particles of an ideal gas is option D  which is The volume of the gas particles is negligible compared with the total volume of the  gas--- ---This gives the reason why  gases  can be compressed. Since there are no  inter molecular forces between them. The particles of an  ideal gas will move at the same random motion  resulting to high pressures, compressing the gas and making the volume negligible or insignificant.

y=3x + 4

Explanation:

Where 3 is the slope and 4 is the y-intercept

Answer:

f = 33.34 Hz

Explanation:

A wave has a period of 0.03 seconds. It is required to find the frequency of a wave. The relation between time period and frequency is inverse. The time period of a wave is given by :

T = 1/f, f = frequency of wave

[tex]f=\dfrac{1}{T}\\\\f=\dfrac{1}{0.03}\\\\f=33.34\ Hz[/tex]

So, the frequency of the wave is 33.34 Hz.

Answer:

[tex]m_{CaF_2}0.375gCaF_2[/tex]

Explanation:

Hello,

In this case, for the studied reaction:

[tex]2KF+Ca(HCO_3)_2\rightarrow CaF_2+2KHCO_3[/tex]

Thus, the first step is to compute the reacting moles of potassium fluoride by using its volume and molarity:

[tex]n_{KF}=0.0157L*0.612\frac{mol}{L} =9.61x10^{-3}molKF[/tex]

Then, we apply the 2:1 molar ratio between potassium fluoride and calcium fluoride to compute the produced moles of calcium fluoride:

[tex]n_{CaF_2}=9.61x10^{-3}molKF*\frac{1molCaF_2}{2molKF} =4.80x10^{-3}molCaF_2[/tex]

Finally, by using the molar mass of calcium fluoride (78.07 g/mol) we can compute its produced grams:

[tex]m_{CaF_2}=4.80x10^{-3}molCaF_2*\frac{78.07gCaF_2}{1molCaF_2} \\\\m_{CaF_2}0.375gCaF_2[/tex]

Best regards.

Answer:

It is neutral (NR)

Explanation:

Salts are formed when the ionizable hydrogens in an acid is replaced by metallic or ammonium ions from bases. The reaction is known as a neutralization reaction.

The nature of a salt formed from this reaction depends on the nature of the reacting acid and base.

If the reaction is between a strong acid and strong base, the salt produced is a neutral salt.

If the reaction occurs between a strong acid and a weak base, the salt produced is acidic.

If the reaction occurs between a strong base and a weak acid, the salt produced is a basic salt.

Considering the salt above, LiNO3.

On hydrolysis, addition of water, the following products are obtained:

LiNO3 + H2O ----> LiOH + HNO3

The products obtained, LiOH and HNO3 are a strong base and a strong acid respectively. Therefore, the salt, LiNO3, is a neutral salt.

The salt, LiNO₃ is a neutral, NR salt as it's a salt formed from the reaction of a strong acid and a strong base.

In neutralisation reactions, acids and bases react to form salt and water.

However, the salt formed may be acidic, basic or neutral. This is dependent on the type of acid and base which form the salt.

A strong acid and a strong base react to yield a neutral salt like, LiNO₃.

The equilibrium equation when LiNO₃ is dissolved in aqeous solution is;

Evidently, LiOH and HNO₃ are an example strong base and acid respectively.

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Answer:

The weakest conjugate is HClO-.

Explanation:

As a general rule, the stronger the Bronsted-Lowry acid, the weaker its conjugate base, and vice versa.  

Acid 1: HClO is a strong acid, hence its conjugate base would be weak

Acid 2: H3PO4 is a weak acid, hence its conjugate base would be strong

Acid 3: hydrogen sulphide is also a moderately weak acid with a moderately strong conjugate base.

In order of increasing strengths:

HClO < H2S < H3PO4

Answer:

C. It decreases by a factor of 4

Explanation:

F1 = kq1*q2/r²

F2 = kq1*q2/(2r)² = kq1*q2/(4r²) = kq1*q2/(r²*4)  = F1/4

Answer:

Time taken = 174 days

Explanation:

Half life is the time take for a subsrtance taken to decay to half of it's origial or initial concentration.

In this probel, the haf life is 87 days, this means that after evry 87 days, the concentration or mass of sulfur-35 decreases by half.

If the starting mass is 1.00g, then we have;

1.00g --> 0.5g (First Half life)

0.5g --> 0.25g (Second half life)

This means that sulphur-335 would undergo two half lives for 0.25g to remain.

Total time taken = Number of half lives  * Half life

Time taken = 2 * 87

Time taken = 174 days

Answer:

2.7 °C

Explanation:

78.4-75.7=2.7

The student's result is 2.7° C less than the expected result.

We have a student conducting an experiment to find the boiling point of ethanol.

We have to determine how far off from the accepted value is the student's result.

Measurement Error (also called Observational Error) is the difference between a measured quantity and its true value.

According to the question, we have -

True value of the boiling point of ethanol [T] = 78.40°C.

Measured value of the boiling point of ethanol [M] = 75.70°C.

The Error (E) in the measurement will be -

E = T - M

E = 78.40° - 75.70° = 2.7° C

Hence, the student's result is 2.7° C less than the expected result.

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Answer:

below

Explanation:

28th 10;24 am

If the Moon rises at 7 P.M. on a particular day, then approximately what time will it rise six days later at 12A.M.

This movement is from the Moon's orbit, which takes 27 days, 7 hours and 43 minutes to go full circle. It causes the Moon to move 12–13 degrees east every day. This shift means Earth has to rotate a little longer to bring the Moon into view, which is why moonrise is about 50 minutes later each day.

So knowing that moonrise is about 50 minutes later each day, we have:

[tex]7+50 minutes = 7:50\\8:40\\9:30\\10:20\\11:10\\12:00 A.M[/tex]

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Compounds formed from non-metals consist of molecules. The atoms in a molecule are joined together by covalent bonds. These bonds form when atoms share pairs of electrons.

Answer:

1 particle of the gas would occupy a volume of 3.718*10⁻²³L

Explanation:

Hello,

1. The sample has a particle of 6.022×10²²particles

2. Volume of the sample = 22.4L

3. Temperature of the sample = 0°C = (0 +273.15)K = 273.15K

4. Pressure of the sample = 1.0atm

What volume would 1 particle of the gas occupy?

But we remember that 1 mole of any substance = 6.022×10²² molecules or particles or atoms

What would be the number of moles for 1 particule?

1 mole = 6.022×10²² particles

X moles = 1 particle

X = (1 × 1) / 6.022×10²² particles

X = 1.66×10⁻²⁴ moles

Therefore, 1 particle contains 1.66×10⁻²⁴ moles

Since we know our number of moles, we can proceed to use ideal gas equation,

Ideal gas equation holds for all ideal gas and is defined as

PV = nRT

P = pressure of the ideal gas

V = volume the gas occupies

n = number of moles of the gas

R = ideal gas constant = 0.082 L.atm / mol.K

T = temperature of the gas

PV = nRT

Solving for V,

V = nRT/ P

We can now plug in our values into the above

equation.

V = (1.66*10⁻²⁴ × 0.082 × 273.15) / 1

V = 3.718*10⁻²³L

Therefore, 1 particule of the gas would occupy a volume of 3.718*10⁻²³L.

Answer:

The correct answer is 15.80 grams.

Explanation:

The reaction taking place in the given question,  

Pb(CH₃COO)₂ + Na₂SO₄ ⇒ PbSO₄ + 2NaCH₃COO

The number of moles can be calculated by using the formula,  

n = weight / molecular mass

Based on the given question, the weight of lead (II) acetate is 23.81 grams and the weight of sodium sulfate is 7.410 grams.  

The number of moles of Pb(CH₃COO)₂ is,  

n = 23.81 g / 325.29 g/mol = 0.0732 moles

The number of moles of Na₂SO₄ is,  

n = 7.410 g / 142.04 g/mol = 0.0521 moles

As one mole of lead (II) acetate needs one mole of sodium sulfate. Therefore, 0.0732 moles of lead (II) acetate needs 0.0732 moles of sodium sulfate.  

However, as sodium sulfate is less, that is, 0.0521, therefore, Na₂SO₄ is a limiting reactant.  

One mole of sodium sulfate produces one mole of PbSO₄. So, 0.0521 moles of Na₂SO₄ produces 0.0521 moles of PbSO₄.  

Now the mass of PbSO₄ is,  

mass = moles × molecular mass

mass = 0.0521 × 303.26 g/mol

mass = 15.80 grams.  

Answer:

Hot material near the core is less dense and rises, when it cools, it becomes more dense and sinks.

Explanation:

This best explains how heat plays a role in the movement of materials within Earth's interior because it's how convection works. Convection is the circular motion that happens when warmer air or liquid which has faster moving molecules, making it less dense rises, while the cooler air or liquid drops down. Convection currents within the earth move layers of magma, and convection in the ocean creates currents.

Earth’s interior is like a closed chamber, hot material near Earth's surface is more denser and sinks, and when it cools, it becomes less dense and Rises.

Convection is the process of heat transfer by the bulk movement of molecules within fluids such as gases and liquids. The heat transfer take place from solid to no solid material. like air and water.

As we take example of home. In home heat take nearer the roof and cold air will be nearer to the flour. It is because of hot is less denser then the cold air. Hot air will become less denser and move towords upside. Cold air become denser move towards down.

Similarly, on earth. Nearer to earth hot materials are more dense and sinks. When it cools, it become less dense and rises.

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Answer:

ΔH°f C₂H₅O₂N(s)  = -537.2kJ

Explanation:

Based on the reaction:

4 C₂H₅O₂N(s) + 9O₂(g) → 8CO₂(g) + 10H₂O(l) + 2N₂(g)

ΔHrxn = ΔH°f products - ΔH°f reactants.

As:

ΔH°fO₂(g) = 0

ΔH°fCO₂(g) = -393.5kJ/mol

ΔH°fH₂O(l) = -285.8kJ/mol

ΔH°fN₂(g) = 0

The ΔHrxn is:

ΔHrxn = (8×-393.5kJ/mol + 10×-285.8kJ/mol) - (4×ΔH°fC₂H₅O₂N(s)) = -3857kJ/mol

-6006kJ/mol - (4×ΔH°fC₂H₅O₂N(s)) = -3857kJ/mol

-4×ΔH°fC₂H₅O₂N(s) = 2149kJ/mol

ΔH°fC₂H₅O₂N(s) = 2149kJ/mol / -4

Answer:

A. 1.54 mole.

B. 55.39g of carbon

Explanation:

A. Determination of the number of mole in 67.7g of C3H8.

Mass of C3H8 = 67.7g

Molar mass of C3H8 = (3x12) + (8x1) = 44g/mol

Number of mole of C3H8 =..?

Number of mole = Mass/Molar Mass

Number of mole of C3H8 = 67.7/44

Number of mole of C3H8 = 1.54 mole

B. Determination of the mass of carbon in the compound.

This is illustrated below:

The mass of C in compound can be obtained as follow:

=> 3C/C3H8 x 67. 7

=> 3x12 / 44 x 67.7

=> 36/44 x 67.7

=> 55.39g

Therefore, 55.39g of carbon is present in the compound.

Answer:

30.0 g.

Explanation:

Hello,

In this case, for us to round the given number off to three significant figures, we firstly realize it has initially five significant figures. Thus, cutting at the third digit, which is the second nine, we will have 29.9 g, nonetheless, as a five is after such nine, we should round the nine to ten, so the result is 30.0 g.

Best regards.

The mass of the atom is calculated by adding the number of protons and neutrons .

The total mass of one atom of an element is defined as its atomic mass. The atomic mass is taken as the mass of protons and neutrons in an atom.

1 a m u = 1.66 ×10⁻²⁴g

To calculate the atomic mass of an element -:

The atomic mass of the single atom can be calculated by adding the total number of protons and the total number of neutrons of that particular atom.

Atomic mass Number = Number of protons + number of neutrons

Hence ,in this way the atomic mass is calculated of an atom .

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Based on the information above provided, the best predictions correct whether a sample of pure tungsten will melt at 3723 K is The sample will mel because T>

Tungsten is a very hard and brittle material. It properties include a very high melting point, a low vapor pressure and the highest hardness and strength of all metals. Tungsten has good corrosion resistance against most acids and alkalis.

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Answer:

well the MF is 224.78 g/mol

Explanation:

just times them all by the molor mass and divide it by 3

Answer:

5.73 g Cu

Explanation:

M(CuSO4) = 159.6 g/mol

M(Al) = 27.0 g/mol

M(Cu) = 63.5 g/mol

14.4 g Al * 1 mol/27.0 g = 0.5333 mol Al

14.4 g CuSO4 * 1 mol/159.6 g = 0.0902 mol CuSO4

                                2 Al         +     3CuSO4 ------->  3Cu + Al2(SO4)3

from reaction           2 mol               3 mol

given                     (0.5333 mol )x       0.0902 mol

needed                   0.0601 mol

x= 2*0.0902/3 = 0.0601 mol   Al

Al is excess, CuSO4 is a limiting reactant.

                               2 Al         +     3CuSO4 ------->  3Cu + Al2(SO4)3

from reaction                               3 mol                  3 mol

given                                            0.0902 mol         x mol

x = 0.0902 mol Cu

0.0902 mol Cu * 1 mol/63.5 g Cu = 5.73 g Cu

Answer:

A. The pH value of rainwater is acidic about 4.4

B. The molar concentrations of the Hydronium ions are more than that of the hydroxide ions. That is why the rainwater is acidic with a pH of less than 7

Explanation:

A. Methyl orange is an acid indicator that is used to detect acidic solutions which have pH values that fall within the range of about 4.4 to 7.  The distinct yellow colour change that was shown by the methyl orange as it was added to the water shows that the pH value is acidic, with a value above 4.4. (it has to be like this before methyl orange changes to  yellow colour)

B. The Hydronium ( H30+) ion concentrations and the hydroxide (OH-) ion concentrations are used to measure the pH values of substances.

We can tell that the Hydronium ( H30+) ion concentrations are more than the hydroxide (OH-) ion concentrations in the sample of rainwater tested. This can be detected from the colour change that both the methyl orange and the litmus paper gave. The indicators showed that the rainwater solution was indeed acidic. Hence, the pH value will be less than 7, but greater than 4.4.

Answer:

The half-life of the material is 2 years

Explanation:

Given;

initial count rate = 2000 decays/minute

final count rate =  500 counts/min

decay time = Four hours

To determine the half life of the material; we create a simple decay table that matches the decay time and count rates.

time (years)                     count rate

0                                    2000 decays/minute

2                                     1000 decays/minute

4                                     500 decays/minute

Half life is the time intervals = 2 years

Also using a formula;

[tex]N = \frac{N_o}{(t/2)^2} \\\\N_o-is \ the \ initial \ count\ rate\\\\N-is \ the \ final \ count\ rate\\\\t/_2 - is \ the\ half\ life \\\\N = \frac{N_o}{(t/2)^2} \\\\500 = \frac{2000}{(t/2)^2}\\\\(t/_2)^2 = \frac{2000}{500} \\\\(t/_2)^2 = 4\\\\t/_2 = \sqrt{4} \\\\t/_2 = 2 \ years[/tex]

Therefore, the half-life of the material is 2 years

Answer:

The correct answer is 5.30 * 10^-4 mol per L.

Explanation:

Based on Henry's law, in a solution solubility of the gas is directly proportional to the pressure, that is, C is directly proportional to P. Here P is the pressure and C is the concentration of the dissolved gases.  

Therefore, it can be written as,  

C2/C1 = P2/P1

Here, C1 is 6.8 * 10^-4 mol/L, P1 is 1 atm and P2 is 0.78 atm, then the value of C2 obtained by putting the values in the equation,  

C2/(6.8*10^-4) = 0.78/1

C2 = 0.78 * 6.8*10^-4

C2 = 5.30 * 10^-4 mol per L.  

Hence, the concentration of dissolved nitrogen at 0.78 atm is 5.30*10^-4 mol/L.