Which example involves phase change in which heat energy is released by the substance?

In conclusion, an experiment about Natural Selection includes mechanisms, explanation, estimation of the frequency of the trait and comparisons.

The scientific method is a series of step used to validate evidence and thus formulate theories.

Darwin used the scientific method to draw conclusions about the main mechanism of evolution, i.e., natural selection.

The scientific method involves making a question, providing an explanation of the hypothesis, making observations/experiments (which include experimental and control groups), and drawing conclusions.

The empirical data serve to test a hypothesis (either confirm or reject it) by contrasting its results with predictive outcomes.

The strength of the conclusions can be enhanced by using supporting evidence from other research fields (in this case, for example, the fossil record).

In conclusion, an experiment on Natural Selection includes mechanisms (question), explanation (hypothesis), estimation of the frequency of the trait in the population (prediction) and comparisons (control group).

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The number of moles of nitrogen that can be produced theoretically will be 3.2655 moles.

The equation of the reaction is as follows:

[tex]2N_2H_4 + N_2O_4 --- > 3N_2 + 4H_2O[/tex]

The mole ratio of [tex]N_2H_4[/tex] reacted to that of [tex]N_2[/tex] produced is 2:3.

Thus, with 2.177 moles of  [tex]N_2H_4[/tex] , the theoretical number of moles of [tex]N_2[/tex] can be calaculated as:

                         3/2 x 2.177 = 3.2655 moles

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0.58 is the molarity of 29.9 g of MgS in 911 mL of solution.

Define the molarity of a solution.

Molarity (M) is the amount of a substance in a certain volume of solution. Molarity is defined as the moles of a solute per litres of a solution. Molarity is also known as the molar concentration of a solution.

Given data:

Volume of solution = 911 mL=0.911L

Given the mass of  MgS = 29.9 g

Molar mass of MgS = 56.38 g/mol

Moles of MgS = 0.5303299042

[tex]Molality = \frac{Moles \;solute}{Volume \;of \;solution \;in \;litre}[/tex]

[tex]Molality = \frac{0.5303299042}{0.911L}[/tex]

Molality = 0.5821403998=0.58

Hence,  0.58 is the molarity of 29.9 g of MgS in 911 mL of solution.

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1) The amount of PbS produced will be 16.27 grams

2: The amount of Fe produced will be 118.72 grams.

1) The equation is balanced. The mole ratio of lead (II) acetate to the PbS is 1:1.

Mole of 22.11 lead acetate = 22.11/ 325.29 = 0.06797 moles

Equivalent mole of PbS = 0.06797 moles

Mass of PbS = 0.06797 x 239.3 = 16.27 grams

2) from the equation, the mole ratio of Al to Fe is 1:1.

Mole of 57.2 g Al = 57.2/26.98 = 2.12 moles

Equivalent mole of Fe = 2.12 moles

Mass of Fe = 2.12 x 56 = 118.72 grams.

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Answer: 69.92 Celsius

Explanation:

Enthalpy change = mass of water * specific heat * change in temperature

400g water * 4.18 J/g*celsius * 1.5K = 2.508kJ

2508 J/(138.3g*0.38 J/g*celsius) = 47.72 K

So the copper temperature was lowered by 47.72K/C when placed in water, so 22.2+47.72 = 69.92 Celsius

Hope this helps(and is correct)!

Answer:

Therefore the theoretical density of iron is 7.877 g/cm³ .

Therefore the number of vacancy per cm³ is

Explanation:

Answer:

776 L H₂O

Explanation:

To find the volume, you need to use the Ideal Gas Law. The equation looks like this:

PV = nRT

In this equation,

-----> P = pressure (atm)

-----> V = volume (L)

-----> n = number of moles

-----> R = constant (0.0821 L*atm/mol*K)

-----> T = temperature (K)

To find the volume of water vapor, you need to (1) convert grams C₅H₁₂ to moles C₅H₁₂ (via molar mass), then (2) convert moles C₅H₁₂ to moles H₂O (via mole-to-mole ratio from reaction coefficients), then (3) calculate volume H₂O (via Ideal Gas Law). The final answer should have 3 sig figs.

(Step 1 & Step 2)

Molar Mass (C₅H₁₂): 5(12.011 g/mol) + 12(1.008 g/mol)

Molar Mass (C₅H₁₂): 72.151 g/mol

1 C₅H₁₂ (g) + 8 O₂ (g) -----> 5 CO₂ (g) + 6 H₂O (g)

273.36 g C₅H₁₂           1 mole            6 moles H₂O
-----------------------  x  ----------------  x  -----------------------  =  22.7 moles H₂O
                                  72.151 g           1 mole C₅H₁₂

(Step 3)

P = 1.01 atm                R = 0.0821 L*atm/mol*K

V = ?                           T = 420 K

n = 22.7 moles

PV = nRT

(1.01 atm)V = (22.7 moles)(0.0821 L*atm/mol*K)(420 K)

(1.01 atm)V = 783.856

V = 776 L

Without units, your answer would be 776.

Answer:

Electrochemical

Combustion

Photosynthesis

Respiration

Explanation:

The scratched tin can with the iron will more rapidly corrode the iron than the tin.

The corrosion can be given as the process of the oxidation of the metal into the more stable metal oxide. The chemical oxidation of the metal is attained with the surrounding available oxygen or the water vapors.

The reactivity of the Iron for the oxidation is more as compared to the tin from the reactivity series. Therefore if both tin and iron are exposed to corrosion, iron will be more rapidly corroded.

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From the calculation, the rate of appearance of Br2 is 1.472 * 10^-3 M s-1

The rate of reaction refers to how fast or slow that reactants disappear or the products are  formed .

Now;

We know that;

-d[NOBr]/dt = 1/2 d[Br2]/dt

Hence;

d[Br2]/dt = 2[-d[NOBr]/dt ]

d[Br2]/dt = 2 (7.36×10-4 M s-1)

d[Br2]/dt =  1.472 * 10^-3 M s-1

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The molecular formula of the compound is C6H6

First, convert the percentages to moles

C = 92.9/12 = 7.74

H = 7.71/1 = 7.71

Thus, the empirical formula will be  CH

[empirical formula]n = molecular formula

Empirical formula mass = 12 + 1 = 13

n = empirical formula mass/molar mass = 78/13 6

Thus, the molecular formula will be C6H6

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Answer:

65.4 mmHg

Explanation:

Using Boyle's Law,

(248)(1.05)=(pressure)(3.98)

pressure = 65.4 mmHg

The net ionic equation of the reaction is:

Net ionic equations are equations where ions which remain in solution known as spectator ions are not shown in the equation. Only ions involved in formation of product are shown.

In the given equation, sodium and nitrate ions are spectator ions.

The net ionic equation of the given reaction is as follows:

In conclusion, spectator ions are not shown in net ionic equation.

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The empirical formula of a compound that has the following percent composition; 81.68% carbon and 18.32% hydrogen is C2H5.

The empirical formula is a notation indicating the ratios of the various elements present in a compound, without regard to the actual numbers.

The empirical formula of a compound that has 81.68% carbon and 18.32% hydrogen can be calculated as follows:

First, we convert mass to moles;

Next, we divide each mole value by the smallest (6.81mol)

We multiply each ratio by 5 to make an whole number:

Therefore, the empirical formula of a compound that has the following percent composition; 81.68% carbon and 18.32% hydrogen is C2H5.

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Answer:

Noble gases are rare elements (gases) with extreme stability and a very low reactivity rate.

Some examples are neon, argon, helium etc.

Hope it helps!!

Answer:

Helium, neon, argon, krypton, xenon, and radon.

Explanation:

The chemical elements in group 18 of the periodic chart are the noble gases. They have the most valence electrons that their outer shell can support, making them the most stable. As a result of their inherent stability, they rarely interact with other components.

Other characteristics of the noble gases are that they all conduct electricity, fluoresce, are odorless and colorless, and are used in many conditions when a stable element is needed to maintain a safe and constant environment. These are the 6 noble gases:

Although the phrase "inert gases" was once used to describe the noble gases, it is not entirely true given that some of them do participate in chemical processes.

Chemical properties:

Under normal circumstances, the noble gases are nonflammable, tasteless, colorless, and odorless. Because it was earlier thought that they had a valence of zero, or that their atoms couldn't mix with those of other elements to create compounds, they were originally given the group 0 designation in the periodic table. However, it was eventually determined that some do in fact combine to create compounds, which led to the label's demise. Full valence electron shells are present in noble gases. The only electrons that often take part in chemical bonding are valence electrons, which are an atom's outermost electrons.  Due to their great stability, complete valence electron shell atoms have little to no inclination to gain or lose electrons and do not frequently establish chemical bonds. But unlike lesser noble gases like helium, larger noble gases like radon are bound together by electromagnetic force less tightly, making it simpler to remove outside electrons from hefty noble gases. The noble gases can be combined with the electron configuration notation to create the noble gas notation as a consequence of a complete shell.

To do this, the electron configuration is written starting with the nearest noble gas that comes before the element in issue, and then it is carried from there. For instance, the noble gas notation is [Ne] 3s2 3p3, whereas the electron notation for phosphorus is 1s2 2s2 2p6 3s2 3p3. In addition to being shorter than writing down the whole notation of atomic orbitals, this more condensed notation makes it simpler to identify elements.

Of all the noble gas compounds that have been created, xenon compounds are the most prevalent. [33] Most of them consist of a xenon atom in the +2, +4, +6, or +8 oxidation state coupled to an extremely electronegative element, such fluorine or oxygen, as in xenon difluoride (XeF).

2), xenon tetrafluoride (XeF

4), xenon hexafluoride (XeF

6), xenon tetroxide (XeO

4), and sodium perxenate (Na

4XeO

6). Xenon reacts with fluorine to form numerous xenon fluorides according to the following equations:

Xe + F2 → XeF2

Xe + 2F2 → XeF4

Xe + 3F2 → XeF6

Some of these compounds have found use in chemical synthesis as oxidizing agents; XeF

2, in particular, is commercially available and can be used as a fluorinating agent.

The moles of ZnCl₂ in 1.5 L of the 0.2 M solution is 0.3 moles.

The moles of ZnCl₂  is present in in 1.5 L of a 0.2 M solution is calculated using the formula below:

Moles of ZnCl₂ = 1.5 x 0.2

Moles of ZnCl₂ = 0.3 moles

In conclusion, the moles of ZnCl₂ in the given volume of solution is determined from the molarity of the solution and the volume of solution.

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Answer:

A

Explanation:

Answer:

its D) all of the above

Explanation:

i learned this is like 6th grade

Answer:

Hierarchies and schemes are important for organizing information. They provide a way to group related information together and to see the relationships between different pieces of information.

[tex]2.3+0.005+0.234+60.12=\boxed{62.659 \text{ g}}[/tex]

The safety feature aimed at keeping nuclear radiation contained is steel-reinforced concrete.

A nuclear power plant is a building with reactors that contain controlled nuclear reactions to produce energy.

Nuclear power plants are able to generate warm water by using atomic properties of matter  (i.e.,m the process of nuclear fission), which is in turn converted into steam to move turbines.

The walls of nuclear power reactors are composed of steel-reinforced concrete in order to avoid radiation release.

In conclusion, the safety standard property that maintains nuclear radiation contained is steel-reinforced concrete.

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At 365 K temperature sulfur tetrafluoride have a density of 0.260 g/L at 0.0721 atm.

The ideal gas law (PV = nRT) relates the macroscopic properties of ideal gases. An ideal gas is a gas in which the particles (a) do not attract or repel one another and (b) take up no space (have no volume).

First, calculate the moles of the gas using the gas law,

PV=nRT, where n is the moles and R is the gas constant. Then divide

the given mass by the number of moles to get molar mass.

Given data:

P= 0.0721 atm

[tex]n=\frac{mass}{molar \;mass}[/tex]

[tex]R= 0.082057338 \;L \;atm \;K^{-1}mol^{-1}[/tex]

T=?

Putting value in the given equation:

[tex]\frac{PV}{RT}=n[/tex]

[tex]density = \frac{2 \;atm\; X molar\; mass}{0.082057338 \;L \;atm \;K^{-1}mol^{-1} X T}[/tex]

[tex]0.260 g/L = \frac{0.0721 \;atm\; X 108.07 g/mol}{0.082057338 \;L \;atm \;K^{-1}mol^{-1} X T}[/tex]

T =  365.2158727 K= 365 K

Hence , at 365 K temperature sulfur tetrafluoride have a density of 0.260 g/L at 0.0721 atm.

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Answer:

yhnjulllljjghbbjygbnk

On the basis of the area and petrified fossils, the following statements are true:

Thus, the correct options are A and D.

Petrified fossils may be defined as those which completely replace the organic form of fossils with mineral forms like stone.

The area was once a forest indicating that there must be a lot of death of organisms that are buried deep into the soil for millions of years.

This area also consists of a huge amount of water for the delocalization of dead organic matter to flow throughout the given area where the organic form is converted into mineral form.

Therefore, the correct options for this question are A and D.

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Answer:

B. 43.40 mL

Explanation:

We are required to determine the volume of 0.200 M Kl(aq).

We have; 155.0 mL of a 0.112 M Pb(NO3)2 solution.

We know that molarity of a solution is contained in 1 L or 1000 mL or 1000 cm³.

Hence,

[tex]x \: mol \: = \frac{155 \times 0.112}{1000} \\ = 0.01736 \: moles[/tex]

= 0.01736 moles of Pb(NO3)2

We have a mole ratio of 2: 1 (KI : Pb(NO3)2).

To obtain the number of moles of KI; we divide by half the moles of Pb(NO3)2 (aq);

(0.01736)/2

= 0.00868 moles KI

0.20 moles KI is contained in 1000 mL

0.00868 moles KI is contained in x mL

[tex]x \: ml \: = \frac{0.00868 \times 1000}{0.20} [/tex]

= 43.40 mL

Therefore the volume of KI required to react completely with 0.112 M Pb(NO3)2 is 43.40 mL

Considering the definition of molar mass,  1.096 moles of Allyl sulfide are in 125 g.

The molar mass of substance is a property defined as its mass per unit quantity of substance, in other words, molar mass is the amount of mass that a substance contains in one mole.

The molar mass of a compound (also called Mass or Molecular Weight) is the sum of the molar mass of the elements that form it (whose value is found in the periodic table) multiplied by the number of times they appear in the compound.

In this case, you know the molar mass of the elements is:

So, the molar mass of the compound C₆H₁₀S is calculated as:

C₆H₁₀S= 6× 12 g/mole + 10× 1 g/mole + 32 g/mole

Solving:

C₆H₁₀S=  114 g/mole

Next, you can apply the following rule of three: If by definition of molar mass 114 grams of the compound are contained in 1 mole, 125 grams of the compound are contained in how many moles?

[tex]amount of moles=\frac{125 grams x 1 mole}{114 grams}[/tex]

amount of moles= 1.096 moles

Finally, 1.096 moles of Allyl sulfide are in 125 g.

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The energy that the water in the  bottle absorbed is obtained as 16800 J.

The specific heat capacity of the water refers to the energy that is required to raise the temperature of 1Kg of the water by 1 degree.

Now we have the following;

mass (m) =  160 g

temperature change dT = ( 35oC -  10oC)

specific heat capacity (c)= 4.2 J/(g * oC).

Now;

H = mcdT

H =  160 g * 4.2 J/(g * oC) *  ( 35oC -  10oC)

H = 16800 J

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An effective scientific model must be testable and verifiable by using the scientific method.

A scientific model is any explanation of an observation of the real world that can be proved by the scientific method.

A scientific model must be testable, which means that we can confirm or reject its assumptions through experimental and/or observational procedures.

In conclusion, the effective scientific model must be proved with the scientific method.

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From the calculation, the pH of the solution is 4.85.

The pH is defined as the hydrogen ion concentration of the solution. We have the ICE table as;

         HA    +    H2O ⇔     H3O^+    +    A^-

I       0.335                          0                0

C     -x                                  +x              +x

E   0.335 - x                         x                x

Ka = 1 * 10^-14/Kb

Ka = 1 * 10^-14/1.8 × 10^–5

Ka = 5.56 * 10^-10

Ka = [H3O^+] [A^-]/[HA]

But  [H3O^+] = [A^-] = x

5.56 * 10^-10 = x^2/ 0.335 - x

5.56 * 10^-10(0.335 - x ) =  x^2

1.86  * 10^-10 - 5.56 * 10^-10x =  x^2

x^2 + 5.56 * 10^-10x - 1.86  * 10^-10 = 0

x=0.000014 M

Now;

pH = -log 0.000014 M

pH = 4.85

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Answer:

11.29 kJ (to 4 sf)

Explanation:

Here, ammonia is the limiting reactant.

For the reaction to occur once, 4 moles of ammonia must be consumed.

Thus means that the reaction can occur 0.1579/4=0.039475 times.

Therefore, (286)(0.039475) = 11.29 kJ (to 4 sf)