What energy is required for a reaction to occur?
A. Bond energy
B. Activation energy
C. Kinetic energy
D. Potential energy

Answer:

Observational study

Explanation:

An investigation of what happened over the years to the people who were exposed to radiation during the 1986 Chernobyl nuclear disaster would be termed an observational study because it will require observing subjects and finding out if there is a kind of correlating factor in the subjects that could indicate the level of exposure to the nuclear radiation.

There are basically two types of research studies:

1. Observational studies

2. Experimental studies

Observational studies involve just the observation of subjects and trying to find out some correlation factors. This kind of study could be prospective when it deals with what could happen in the future based on certain factors or retrospective when it considers what has already happened. An observational study can be cross-sectional, case-only, case-control, or cohort study.

Experimental studies are also referred to as randomized or controlled trial studies. Here, subjects are grouped and each group receives a different treatment in order to isolate the effect of a particular factor or variable relating to the treatment.

Answer:

Animals need food, water, shelter, and space to survive. Herbivores can live only where plant food is available. Carnivores can live only where they can catch their food. Omnivores can live in many places because they eat both plants and animals.

Answer:

Partial pressure of neon = 175 mmHg

Partial pressure of xenon = 564 mmHg

Explanation:

The partial pressure of a gas in a mixture can be calculated as the product of the mole fraction of the gas (Xi) and the total pressure (Pt), as follows:

Pi = Xi Pt

The total pressure is 739 mmHg ⇒ Pt =  739 mmHg

In order to calculate the mole fraction of each gas, we have to first calculate the number of moles of each gas (n) by dividing the mass of the gas into the molar mass (MM):

For neon gas (Ne):

MM(Ne) = 20.18 g/mol

n(Ne)= mass/MM = 0.919 g x 1 mol/20.18 g = 0.045 mol Ne

For xenon gas (Xe):

MM(Xe) = 131.3 g/mol

n(Xe)= mass/MM = 19.1 g x 1 mol/131.3 g = 0.145 mol Xe

Now, we calculate the mole fraction (X) by dividing the number of moles of the gas into the total number of moles (nt):

nt= moles Ne + moles Xe = 0.045 mol + 0.145 mol = 0.190 mol

X(Ne) = moles Ne/nt = 0.045 mol/0.190 mol = 0.237

X(Xe) = moles Xe/nt = 0.145/0.190 mol = 0.763

Finally, we calculate the partial pressures of Ne and Xe as follows:

P(Ne) = X(Ne) x Pt = 0.237 x 739 mmHg = 175 mmHg

P(Xe) = X(Xe) x Pt = 0.763 x 739 mmHg = 564 mmHg

Answer:

[tex]\% Fe=48.2\%[/tex]

Explanation:

Hello!

In this case, since the percent composition of an element in a compound is given by:

[tex]\% i =\frac{z_i*m_i}{MM}*100\%[/tex]

Whereas i represent the element in the compound for which we want compute the mass percent. As required for siderite, FeCO3 whose molar mass is 115.854 g/mol, and knowing there is one iron atom there with an atomic mass od 55.85 g/mol, the mass percent of iron there is:

[tex]\% Fe=\frac{1*55.85}{115.854}*100\%\\\\\% Fe=48.2\%[/tex]

Best regards!

Answer:

1.45 Atmospheres = 146.92125 Kilopascals, or about 146.9 Kilopascals

Explanation:

1 Atmosphere = 101.325 Kilopascals, so 101.325 Kilopascals x 1.45 Atmospheres = 146.92125 Kilopascals.

Using the conversion table, the pressure of the compressed gas at 1.45 atm when converted to kilopascal becomes 146.92 kPa.

Atm is the standard atmosphere which is a unit of pressure.

From conversion table

1 atm atmospheric pressure is equivalent to 101.325 kPa ( kilopascal ).

Now, the pressure of the compressed gas at 1.45 atm will be;

P = 1.45 × 101.325 kPa

P = 146.92 kPa

Therefore, the pressure of the compressed gas at 1.45 atm when converted to kilopascal using the conversion table becomes 146.92 kPa.

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Answer: 51.9961 g/mol, don't know if it helps :)

Explanation:

Answer:

Chromium is a steel-gray, lustrous, hard metal that takes a high polish, is fusible with difficulty, and is resistant to corrosion and tarnishing.

The most common oxidation states of chromium are +2, +3, and +6, with +3 being the most stable. +4 and +5 are relatively rare. Chromium compounds of oxidation state 6 are powerful oxidants.ion:

Answer:

[tex]C_{zinc}=0.400\frac{J}{g\°C}[/tex]

Explanation:

Hello!

In this case, by considering thermodynamics and the temperature of zinc, we can infer it is hot while water is cold, it means that the heat lost by the zinc is gained by the water and we can write:

[tex]Q_{Zn}=-Q_{water}[/tex]

In terms of mass, specific heat and temperatures we can write:

[tex]m_{Zn}C_{Zn}(T_{eq}-T_{Zn})=-m_{water}C_{water}(T_{eq}-T_{water})[/tex]

In such a way, by solving for the specific heat capacity of the zinc we write:

[tex]C_{zinc}=\frac{-m_{water}C_{water}(T_{eq}-T_{water})}{m_{Zn}(T_{eq}-T_{Zn})}[/tex]

Thus, by plugging in the given values we obtain:

[tex]C_{zinc}=\frac{-45.0g*4.184\frac{J}{g\°C}* (27.1\°C-98.8\°C)}{13.8g*(27.1\°C-98.8\°C)}\\\\C_{zinc}=0.400\frac{J}{g\°C}[/tex]

Best regards!

Answer:

These are called isotopes. They have the same number of protons (and electrons), but different numbers of neutrons. Different isotopes of the same element have different masses. Mass is the word for how much substance (or matter) something has.

Answer:

ΔH= -390.3kJ

Explanation:

Using Hess's law, we can obtain ΔHrxn from the sum of related reactions.

Using:

(1) C(s) + 2H2(g) → CH4(g) ΔH=−74.6kJ

(2) C(s) + 2Cl2(g) → CCl4(g) ΔH=−95.7kJ

(3) H2(g) + Cl2(g) → 2HCl(g) ΔH=−184.6kJ

(2) - (1):

CH4(g) + C(s) + 2Cl2(g) → CCl4(g) + C(s) + 2H2(g)

CH4(g) + 2Cl2(g) → CCl4(g) + 2H2(g)

ΔH= -95.7kJ - (-74.6kJ) = -21.1kJ

This reaction + 2*(3):

2H2(g) + 2Cl2(g) + CH4(g) + 2Cl2(g) → CCl4(g) + 2H2(g) +4HCl(g)

CH4(g) + 4Cl2(g) → CCl4(g) + 4HCl(g)

ΔH= -21.1kJ + 2*-184.6kJ

Answer:

76.366

Explanation:

Knewton answer is 76.4

Answer:

76.4mL

Explanation:

First, calculate the final number of moles of carbon dioxide (n2) in the container.

n2 = n1+n added = 3.41×(10^-3) mol+8.41×(10^-4) mol = 4.25×(10^-3) mol

Rearrange Avogadro's law to solve for V1.

V1 =(V2×n1)/n2

Substitute in the known values for n1, V2, and n2.

V1 = (95.2mL×(3.41×10^-3 mol))/(4.25×(10^-3) mol)=76.4mL

So the initial volume is 76.4mL.

Answer:

C

Explanation:

Al=Aluminum

Mg=Magnesium

Answer:

Atoms in group 2a are likely to form ions with a +2 charge because they have two valence electrons, both of which experience a very weak pull from the nucleus due to electron shielding. This causes the atoms to be easily pulled away from the nucleus, creating the +2 ions we see in nature.

Atoms in group 7a are likely to form ions with a -1 charge because they are one electron away from completing their outermost shell. The large number of protons in the middle of these atoms also causes the valence electrons to experience a stronger net force. This force also pulls strongly on the valence electrons of other atoms, causing the -1 ions we see in nature.

Answer:

39.1-32.5 and you will find your answer it always like that, you subtract your starting point from your ending point

Explanation:

The volume of the piece of lead is 6.6 mL

From the question given above, the following data were obtained:

The volume of the lead can be obtained as follow:

Volume of lead = (Volume of water + Lead) – (Volume of water)

Volume of lead = 39.1 – 32.5

Volume of lead = 6.6 mL

Therefore the volume of the lead is 6.6 mL

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Answer:

He won 32 games.

Explanation:

Another way of expressing 75% is 75/100.

To calculate how many games the baseball pitcher won, we multiply the total of games played (43, in this case) by the percent won:

43 * 75/100 = 32.25 ≅ 32

So the baseball pitcher won 32 games.

Answer:

oxygen, silicon, iron, calcium, sodium

Explanation:

these are all found in space rocks known as meteorites. hope this helps :)

Answer:

geruow0irghvn3p0unhie0ghik

Explanation:

Answer:

Because elements cannot decompose

Explanation:

Elements are distinct substances that cannot be split-up into simpler substances. Such substances are only made up of one atom.

The number of mole of NaCl needed to react with excess Pb²⁺ to produce 45.5 g of PbCl₂ is 0.328 mole

We'll begin by calculating the number of mole in 45.5 g of PbCl₂. This can be obtained as follow:

Mass of PbCl₂ = 45.5 g

Molar mass of PbCl₂ = 207 + (35.5×2) = 278 g/mol

Mole = mass / molar mass

Mole of PbCl₂ = 45.5 / 278

2NaCl + Pb²⁺ —> PbCl₂ + 2Na⁺

From the balanced equation above,

2 moles of NaCl reacted to produce 1 mole of PbCl₂

Therefore,

Xmol of NaCl will react to produce 0.164 mole of PbCl₂ i.e

Xmol of NaCl = 2 × 0.164

Xmol of NaCl = 0.328 mole

Thus, the number of mole of NaCl needed for the reaction is 0.328 mole

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Answer:

B- beaker

Explanation:

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Answer:

jajjsjsjddjdjdjdjdjjdjeieiririitofodoslwnridooskemridisoskswkwjj jwjwiwiwiwkiwiw

Question: How many atoms of sodium (Na) are there on either side of the equation?

Options: A) one B) two C) four D) six

Correct answer: D) six

Answer:

It is NOT six, i took the test and got it wrong. The CORRECT answer is 2

Explanation:

Answer:

m = 0.00659 kg = 6.59 g

Explanation:

From Faraday's Law of Electrolysis, we know that:

m = ZQ

where,

m = mass of silver deposited = ?

Q = charge supplied = (1.65 A-hr)(3600 s/1 hr) = 5940 C

Z = electrochemical equivalent of silver = 1.18 x 10⁻⁶ kg/C

Therefore,

m = (1.11 x 10⁻⁶ kg/C)(5940 C)

m = 0.00659 kg = 6.59 g

The mass of silver that would be deposited by a battery is 6.65 grams

The precipitation of Ag requires the removal of one electron. The reduction process for silver electrode at the cathode is as follows:

[tex]\mathbf{Ag^+ + e^- \to Ag(s)}[/tex]

∴

In one mole of an electron, the charge carried = 96500 C

Recall that:

The atomic mass of silver (Ag) = 108 g

∴

The mass of silver that would be deposited in a 5940 C can be computed as:

[tex]\mathbf{=5940\ C \times \dfrac{108 \ g }{96500 \ C}}[/tex]

= 6.65 grams

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Answer:

Explanation:

The chemical expression for the reaction between iron and oxygen is:

4Fe(s)  +  3O₂ (g)  [tex]\to[/tex] 2Fe₂O₃ (s)

The number of moles of Fe = mass of Fe/ molecular mass of Fe

The number of moles of Fe = 56 g/ 55.845 g/mol

The number of moles of Fe = 1.002 moles of Fe

The number of moles of oxygen = mass of oxygen/ molecular mass of oxygen

The number of moles of oxygen = 156 g /32 g/mol

The number of moles of oxygen = 4.875 moles of oxygen

Assume that Fe is the limiting reactant, the number of Fe₂O₃ can be calculated as:

moles of Fe₂O₃ = 1.002 mole of Fe × 2 moles of Fe₂O₃/ 4 moles of Fe

moles of Fe₂O₃ = 0.501 mole of Fe₂O₃

Assume that O₂ is the limiting factor, the number of Fe₂O₃ is:

moles of Fe₂O₃ = 4.875 moles of O₂ × 2 moles of Fe₂O₃/ 3 moles of O₂

moles of Fe₂O₃ = 3.25 mole of Fe₂O₃

Thus, after the reaction is complete, Fe and O₂ contain different moles of Fe₂O₃. Only Fe gets consumed in the reaction and it is the limiting factor.

Answer:

100Jkg/°C

Explanation:

Given parameters:

Mass of metal  = 2kg

Amount of heat energy  = 1600J

Initial temperature  = 5°C

Final temperature = 13°C

Unknown:

Specific heat capacity of the metal  = ?

Solution:

Specific heat capacity of a body is the amount of heat needed to raise the temperature of unit mass of a body by 1°C.

  H  = m x C x (T₂ - T₁ )

H is the amount of heat

m is the mass

C is the unknown specific heat capacity

T is the temperature

     Insert the parameters and solve;

  1600 = 2 x C x (13 - 5)

   1600  = 16C

        C = 100Jkg/°C

Answer:

Explanation:

The number of S atoms can be found by using the formula

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question we have

N = 0.67 × 6.02 × 10²³

We have the final answer as

Hope this helps you

The ions are able to move freely from one place to another. So that they conduct electricity. But the molecular solutions does not electricity.

The molecular solution is composed of molecules and consists of non - metallic atoms. These atoms are held together by the covalent bonds. The flow of charged particles is responsible for the conduction of electricity. If there is no flow of electrons or ions then there will be no electricity.

In the molecular solutions, the molecules present are not dissociated into respective ions. Since the molecules are not converted into the charged particles no electricity is produced.

A molecular solution is regarded as a non-electrolyte which does not contain ions. But electrolytes are dissociated into ions and thereby conducts electricity. So all electrolytes are good conductors of electricity.

Thus molecular solution does not contain ions.

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Answer:

Antoine Lavoisier

1) Law of Conservation of Mass

French chemist, Antoine Lavoisier in 1789, studied this law. This law states that “In all physical and chemical changes, the total mass of the reactants is equal to that of the products” or “Mass can neither be created nor destroyed.”