Which statement accurately describes the Doppler effect?

Answer:

true.

Explanation:

The total path covered by an object during its entire journey is called the distance covered. It is equal to the sum of all path traveled.

A person runs 21.0 km west then turns around and runs 10.0 km east. The total distance covered will be the sum of 21 km and 10 km.

d = 21 km + 10 km

d = 31 km

Hence, the given statement is true.

Answer:

See explanation

Explanation:

The shorthand nuclear reaction equations have been given; the first particle in the parentheses is a reactant particle while the second particle is a product particle. These can now be rewritten as the longhand equations as follows;

238/92U + 4/2 He -------> 241/94Pu + 1/0 n

238/92U + 4/2 He ------> 241/94Pu + 1/0 n

14/7N + 4/2 He------> 17/8O + 1/1 p

56/26Fe + 2 4/2 He----> 60/29Cu + 4/2 He

Answer:

It takes 1,068.76 grams of nitrogen to fill an 855 L tank at STP.

Explanation:

The STP conditions refer to the standard temperature and pressure. Pressure values at 1 atmosphere and temperature at 0 ° C or 273.15 °K are used and are reference values for gases.

On the other side, the pressure, P, the temperature, T, and the volume, V, of an ideal gas, are related by a simple formula called the ideal gas law:  

P*V = n*R*T

where P is the gas pressure, V is the volume that occupies, T is its temperature, R is the ideal gas constant, and n is the number of moles of the gas.

So, in this case:

Replacing:

1 atm* 855 L= n* 0.082 [tex]\frac{atm*L}{mol*K}[/tex] * 273.15 K

Solving:

[tex]n=\frac{1 atm* 855 L}{0.082\frac{atm*L}{mol*K} *273.15 K }[/tex]

n= 38.17 moles

Being the molar mass of nitrogen N2 equal to 28 g / mol, you can apply the following rule of three: if there are 28 grams in 1 mole, how much mass is there in 38.17 moles?

[tex]mass=\frac{38.17 moles*28 grams}{1 mole}[/tex]

mass= 1,068.76 grams

It takes 1,068.76 grams of nitrogen to fill an 855 L tank at STP.

Answer:

A-210, n-125

A-207, n-122

A-209, n-124

Explanation:

The mass number is the sum of the number of protons and neutrons in the nucleus of an atom.

Astatine has an atomic number of 85, this is the number of protons in its nucleus. We must subtract the given number of neutrons in each option from the mass number and consider the difference. If the difference between the mass number and number of neutrons is exactly 85, then that option represents one of the isotopes of astatine.

Answer:

a) pH = 9.44

b) 25mL of HBr are required.

c) pH = 5.37

d) pH = 9.26

Explanation:

The equilibrium of NH₃ in water occurs as follows:

NH₃(aq) + H₂O(l) ⇄ NH₄⁺(aq) + OH⁻(aq)

Kb = 1.8x10⁻⁵ = [NH₄⁺] [OH⁻] / [NH₃]

The reaction of NH₃ with HBr is:

NH₃ + HBr ⇄ NH₄⁺ + Br⁻

That means when you add X moles of HBr before to reach the equivalence point, the moles are:

Moles NH₃ = Initial moles - moles HBr

Moles NH₄⁺ = Moles HBr

Initial moles NH₃ = 0.050L * (0.05mol / L) = 2.5x10⁻³ moles NH₃

Moles HBr = 0.010L * (0.10mol / L) = 1x10⁻³ moles HBr

Thus, after the reaction:

Moles NH₃ = 1.5x10⁻³moles

Moles NH₄⁺ = 1x10⁻³ moles

Using Henderson-Hasselbalch equation, pH of this solution is:

pOH = pKb + log [NH₄⁺] / [NH₃]

Where pKb is -log Kb = 4.74

And [] could be taken as moles of each compound:

pOH = 4.74 + log [1x10⁻³ moles] / [1.5x10⁻³ moles]

pOH = 4.56

And pH = 14 - 4.56

b) To reach equivalence point, we need to add 2.5x10⁻³ moles HBr:

2.5x10⁻³ moles HBr * (1L / 0.10mol) = 0.025L = 25mL of HBr are required

c)At equivalence point, you will have just 2.5x10⁻³ moles of NH₄⁺ in 50.0mL + 25mL = 75mL. The molar mass of NH₄⁺ is:

[NH₄⁺] = 2.5x10⁻³mol / 0.075L = 0.0333M

The equilibrium of NH₄⁺ is:

NH₄⁺ ⇄ NH₃ + H⁺

Ka = [NH₃] [H⁺] / [NH₄⁺] = 5.556x10⁻¹⁰

[NH₃] = [H⁺] because both comes from the same equilibrium and [NH₄⁺] = 0.0333M:

[X] [X] / [0.0333M] = 5.556x10⁻¹⁰

[X]² = 1.85x10⁻¹¹M

[X] = [H⁺] = 4.3x10⁻¹¹M

pH = -log [H⁺] = 5.37

d) At midpoint, [NH₃] = [NH₄⁺]. Using H-H equation:

pOH = 4.74 + log [NH₃] / [NH₄⁺]

pOH = 4.74

And pH = 14 - 4.74

Answer:

Atom is the smallest particle of pure sustance which can take part in a chemical reaction.A chrged atom is called an ion.

A molecule of an element or compound is the smallest particle of it that is stable and capable of independent existence. The molecules of element and compound are different.

Answer: Since one molecule of CO2 contains one molecule carbon atoms, therefore, 0.6 molecule of carbon dioxide will contain 0.6 molecule of carbon.

Mass of C in 0.6 molecule of CO2

Explanation

= No. Of molecule × molar mass

= 0.6× 12gm

=7.2gm

Answer:

The temperature is always lower.

Explanation:

The temperature is always lower at the end of the state as compared to beginning of the state. We can see in the given data, the temperature is higher at the beginning i. e. 140 degree Celsius but with the passage of time, the temperature of a state decreases constantly  and the temperature at the end is lower i. e. 20 degree Celsius. So we can conclude that the temperature is always lower.

We want to study how the temperature behaves in a change of phase. Ideally, we would read a graph and use the given information, but we can't see the graph, so for the answer, I will use a general thermodynamics knowledge instead of the missing graph.

We will see that the correct option is: The temperature is always the same

---------------------------------------

Let's start by explaining how temperature manifests in objects.

Assume we have something in solid phase. As we increase the temperature, the particles on the solid increase their kinetic energy, thus, the particles move more.

This causes that the volume of the object increases (for example when we heat up a metal and it dilates). This keeps happening until we reach a critical point, when we are near a change of phase.

At this point the energy given is not used to increase the temperature of the object, but is used to "break" bonds in such a way that the particles are more free than before. When all these bonds are "broken" the change of phase is completed, and in the case of the solid, we go from solid phase to liquid phase.

An example of this is that we can have liquid water and solid water both at 0°C, so if you have a thermometer in your home, an experiment that you can do is:

Put water in the refrigerator.

Note when the liquid water reaches 0°C

As the water starts to solidify, keep recording its temperature, you will see that it does not change (a lot, it may change a little bit) until all the water changes of phase.

So to answer this;

how does the temperature at the beginning of a change of state compare with the temperature at the end of the change?

The temperature is always the same

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Answer:

[tex]m=243.72g[/tex]

Explanation:

Hello,

For the given chemical reaction:

[tex]CaO(s) + 3 C(s) \rightarrow CaC_2(s) + CO(g)[/tex]

Whose heat of reaction is 464.8 kJ/mol which means that energy is absorbed due to the chemical reaction, we can compute the moles of calcium carbide via the following relationship:

[tex]n=\frac{1770kJ}{464.8 kJ/mol}\\ \\n=3.81mol[/tex]

Then, since the molar mass of calcium carbide is 64 g/mol, the yielded mass turns out:

[tex]m=3.81mol*\frac{64g}{1mol}\\ \\m=243.72g[/tex]

Best regards.

Answer:

This question is incomplete and it lacks options. The complete question is as follows;

In condensation reactions, the atoms that make up a water molecule are from what?

a. oxygen

b. only one of the reactants

c. both of the reactants

d. carbohydrates

e. enzymes

The answer is C. Both of the reactant

Explanation:

In a chemical reaction, two small molecules called monomers combine to form a much larger molecule called polymer in a process called CONDENSATION REACTION. Some condensation reactions is characterized by the release of a water molecule (dehydration).

This water molecule is formed as a result of the active participation of both reactants. During the reaction, hydroxyll group (-OH) from one of the reactants breaks off and combines with hydrogen ion (H+) from the other reactant to form water molecule (H2O).

Hence, the atoms that make up the water molecule come from both of the reactants participating in the condensation reaction.

Answer:

Sociologist view that an individual is a reflection of a society to which he or she have belonged.

Explanation:

It is not an individual or a society, but both of them together allows us to reveal the fundamentals of human existence. The extreme view of the person or society has been discarded for quite some time. The concept of society indicates a reciprocal giving-and-take by the individuals involved in the form of mutual corporations, interaction, or the more subtle types of social interaction such as letter writing, festival greeting, sending and accepting presents, telephone communication, e-mailing, internet chatting, and public relations engagement.

Answer:

Explanation:

All atoms (except for group 0 elements) of elements tend to achieve stability by having there outermost shell completely filled; achieving an octet configuration. During chemical bonding, atoms tend to achieve stability majorly in one of the two ways below

1) Ionic or electrovalent bonding: This involves the transfer of electrons from a positively charged ion (cation) to a negatively charged ion (anion). Here, no molecule is formed. For instance, in the formation of a sodium chloride (NaCl) salt. Sodium ion donates the single electron on it's outermost shell (to achieve it's octet configuration) to chloride ion (which needs just one more electron in it's outermost shell to achieve it's octet configuration).

Na⁺ + Cl⁻ ⇒ NaCl

2) Covalent bond: This involves the sharing of lone pair of electrons between two atoms to form a molecule. For example, the outermost shell of an oxygen atom, has two single electrons (that are not in pair), these single electrons can form covalent bond independently with hydrogen atoms (to form water) that also have just one electron in their shells. Hence, at every "covalent bonding site", an electron from oxygen and an electron of hydrogen is shared between the two atoms in order to achieve a stable configuration (Here, we have two "covalent bonding sites").

Answer:

non polar and neutral polar and neutral acidic and polar basic and polar

Answer:

C

Explanation:

just took the test

The pair of chemical elements which would most likely combine to form a salt is: Cs and I.

An inorganic substance can be defined as a substance that doesn't contain both carbon and hydrogen.

In Chemistry, some examples of an inorganic compound include the following:

A salt comprises an ionic assembly of both the negative ion (anion) of an acid and a positive ion (cation) of a base, which results in the formation of a neutral chemical compound.

Hence, cesium (Cs) which has a a positive charge of one (+1) and an iodine (I) ion with a negative charge of one (-1) would combine or react to form neutral cesium iodide (CsI).

In conclusion, a salt is most likely to be formed from the reaction of cesium (Cs) and iodine (I).

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Answer:

1600

Explanation:

5×10^4÷2.5×10^2

(5×10^4)

(10^4)

(5×40)

(200)

(200÷2.5)

(80)

(80×10^2)

(10^2)

(20)

(80×20)

Answer is 1600.

Sorry if it's not correct.

Answer:

287.6g CHCl₃

Explanation:

We can determine the structure of Chloroform, dividing the mass of each element in its molar mass:

C = 12.0g * (1mol /12g) = 1 mol C

H = 1.01g * (1mol / 1.01g) = 1 mol H

Cl = 106.4g * (1mol / 35.45g) = 3 moles Cl

The structure is CHCl₃. And its molar mass is: 12.0g C +1.01g H + 106.4g Cl = 119.41g/mol

Now, the moles of carbon in the second sample = Moles of chloroform are:

28.9g C * (1mol / 12g) = 2.408 moles C = Moles CHCl₃

And its mass is:

2.408 moles CHCl₃ * (119.41g/mol) =

Answer:

analyze

Explanation:

After testing is analyzing your data then you compare your data to your hypothesis to see if they match  

Answer:

A. No precipitate is formed

Explanation:

Hello,

In this case, since the reactions are:

[tex]Ca^{2+}(aq)+2HCl(aq)\rightarrow CaCl_2(aq)+2H^+(aq)\\\\Ba^{2+}(aq)+2HCl(aq)\rightarrow BaCl_2(aq)+2H^+(aq)[/tex]

We evidence no formation of insoluble salts or precipitates since both calcium and barium chlorides are largely soluble in water due to the ionic bond which binds them, thus A. No precipitate is formed.

Regards.

Answer:

the answer is A

Answer:

An increase

Explanation:

The strong southerly winds affect the vapor pressure by increasing it .

When the vapor pressure increases it means an increase in temperature and more evaporation occurs.

A decrease in the vapor pressure means a reduction in temperature with less amount of evaporation being involved

Answer:

Strong acids are 100% ionized in water.

Explanation:

A strong acid is any acid that is completely ionized in water (achieves 100% ionization). Weak acids do not ionize completely in water. Many weak acids ionize to a very small extent in pure water.

Examples of strong acids are HCl, H2SO4, HNO3, etc.

Answer:

E) water molecules can cluster about cations and anions.

Explanation:

Electrolytes are substance that when dissolved in water gives ion.which is cation and anion.

As they disolve in water the water molecules cluster about about cations and anions. As a result of the movement of ions they produce electricity.

Electrolytes are substances that dissociate into ions when dissolved in water. The correct answer is "Water molecules can cluster around cations and anions."

These ions are electrically charged particles, with cations carrying a positive charge and anions carrying a negative charge. When an electrolyte dissolves in water, the water molecules surround and interact with the ions.

Water molecules have a polar nature, with a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. These polar water molecules can cluster around the charged ions, forming a hydration shell. The positive ends of water molecules (hydrogen atoms) are attracted to anions, while the negative ends (oxygen atoms) are attracted to cations.

This clustering of water molecules around the ions is due to the electrostatic forces of attraction between the charged particles and the polar water molecules. This phenomenon helps to stabilize the ions in solution and enables the electrolyte to dissolve readily in water.

Therefore, the correct answer is that electrolytes dissolve readily in water because water molecules can cluster around both cations and anions.

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Answer:

0.000128 kilometers

Answer:

0.000128 kilometre..

The three main lines of evidence for revolution is Darwin used multiple lines of evidence to support his theory of evolution by natural selection -- fossil evidence, biogeographical evidence, and anatomical evidence.

The three main lines of evidence for evolution is fossil evidence, biogeographical evidence and anatomical evidence.

In biology evolution is a process in which change in the characterisitics of any species over a several generation on the basis of natural selection method.

The three main lines of evidence for evolution are:

So, three lines of evidences are fossil evidence, biogeographical evidence and anatomical evidence.

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Answer:

B

Explanation:

Sea level changes due to many different  geological events  and can rise or fall over time .

Sea level changes due to global warming , the water being added to the seas as the glaciers melts due to global warming and the expansion of water when it warms.

The sea level also increases due to land processes like soil erosion ,oil and ground water pumping.Changes in land water storage like dams ,changes in global precipitation patterns also make a significant contribution  to change in sea level.

The increased emission of green house gases is a dominant cause  for change in sea level.Fifty percent of sea level rise is due to thermal expansion of seas and the rest is due to the geological activities.

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Answer:

Explanation:

Three temperature scales are currently in use. Their units are °F (degrees Fahrenheit), °C (degrees Celsius), and K (kelvin). The Fahrenheit scale, which is the most commonly used scale in the United States outside the laboratory, defines the normal freezing and boiling points of water to be exactly 32°F and 212°F, respectively.

The Celsius scale divides the range between the freezing point (0°C) and boiling point (100°C) of water into 100 degrees. The kelvin is the SI base unit of temperature: it is the absolute temperature scale. By absolute we mean that the zero on the Kelvin scale, denoted by 0 K, is the lowest temperature that can be attained theoretically. On the other hand, 0°F and 0°C are based on the behavior of an arbitrarily chosen substance, water.

The size of a degree on the Fahrenheit scale is only 100/180, or 5/9, of a degree on the Celsius scale. To convert degrees Fahrenheit to degrees Celsius, we write:

?ºC = (ºF - 32ºF) * 5ºC/9ºF

The following equation is used to convert degrees Celsius to degrees Fahrenheit:

?ºF = 9ºF/5ºC * (ºC) + 32 ºF

Both the Celsius and the Kelvin scales have units of equal magnitude; that is, one degree Celsius is equivalent to one kelvin. Experimental studies have shown that absolute zero on the Kelvin scale is equivalent to –273.15°C on the Celsius scale.

Thus, we can use the following equation to convert degrees Celsius to kelvin:

?K = (ºC +273.15ºC) * 1K/1ºC