Which physical change is endothermic?

A) CO2(l) → CO2(s)

B) CO2(g) → CO2(s)

C) CO2(g) → CO2(l)

D) CO2(s) → CO2(g)

Answer:

Subtract the atomic number (the number of protons) from the rounded atomic weight. This gives you the number of neutrons in the most common isotope. Use the interactive periodic table at The Berkeley Laboratory Isotopes Project to find what other isotopes of that element exist.

Explanation:

Forms of the same atom that differ only in their number of neutrons are called isotopes. Together, the number of protons and the number of neutrons determine an element's mass number: mass number = protons + neutrons.

Answer:

the answer is....... D. Plasma

Answer:

Plasma

Explanation:

Got it right

The net change in enthalpy for the formation of one mole of lead(ii) sulfate from lead, lead(iv) oxide, and sulfuric acid is -274.5 KJ,

Calculation

Reaction 1: [tex]H_{2} SO_{4(aq)}--- > SO_{3(g)} +H_{2} O_{(l)}[/tex] ,  Δ[tex]H^{Q} = +113 KJ[/tex]

Reaction 2: [tex]Pb_{(s)} +PbO_{2(s)} +2SO_{3(s)} --- > 2PbSO_{4(aq)}[/tex] Δ[tex]H^{Q} =-775 KJ[/tex]

To calculate the net change in enthalpy for the formation of 1 mole of [tex]PbSO_{4(aq)}[/tex]

Divide reaction 2 by  2

⇒[tex]\frac{Pb_{(s)}}{2} +\frac{PbO_{2(s)}}{2} +\frac{2SO_{3(s)}}{2} --- > \frac{2PbSO_{4(aq)}}{2}[/tex],  Δ[tex]H^{Q} =\frac{-775}{2} KJ[/tex]

⇒[tex]\frac{Pb_{(s)}}{2} +\frac{PbO_{2(s)}}{2} +SO_{3(s) --- > PbSO_{4(aq)[/tex] , Δ[tex]H^{Q} =-387.5 KJ[/tex]

Subtract reaction 1 with the above reaction

[tex]H_{2} SO_{4(aq)}--- > SO_{3(g)} +H_{2} O_{(l)}-\frac{Pb_{(s)}}{2} +\frac{PbO_{2(s)}}{2} +SO_{3(s) --- > PbSO_{4(aq)[/tex]

⇒[tex]H_{2} SO_{4(aq)}+\frac{Pb_{(s)}}{2}+\frac{PbO_{2(s)}}{2} --- > PbSO_{4(aq)}+H_{2} O_{(l)}[/tex]

Δ[tex]H^{Q}[/tex]=Δ[tex]H^{Q} Product[/tex]+Δ[tex]H^{Q} Rreactant= -387.5 KJ+113 KJ[/tex]

Δ[tex]H_{formation} =-274.5 KJ[/tex]

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Chemical compounds are created when elements combine and are frequently separated into two groups. Ionic compounds are frequently created when metals and nonmetals react.

These substances are made of neutral atoms and molecules that have had their electrons added to or taken away to generate positive and negative ions.

The mantle and the solid inner core are separated by this layer of the planet. It is the sole liquid layer, a 1,400 mile sea made largely of iron and nickel. Iron and nickel make up the majority of the lava. The magnetic field of the Earth is produced by the outer core. The inner core, which is the last layer, is 900 miles deep. According to scientists, the inner core is a solid ball of minerals and iron.

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From the comparison of methane and hydrogen gases, it is found that Hydrogen gas, H₂ will be the best fuel

From the given question, we have:

CH4 and H₂ have fuel values as following;

For CH4=55.5mj/kg

For H[tex]_{2}[/tex]=142mj/kg

When we combust CH4 It will produce CO[tex]_{2}[/tex] gas and water as a product. The CO[tex]_{2}[/tex] gas is an environment pollutant and it also has low fuel value

However, if we combust H₂, It will produce only H₂O, which is environmentally healthy and also produces more fuel value.

Hence, H₂ will be the best fuel

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This chemical equation is balanced.

What is chemical equation?

chemical equation are symbolic representation of chemical reactions in which the reactants and the product are expressed in term of their respective chemical formula.

Reactants are converted to products and the process is symbolise by a chemical equation.

Sol-

NH^3+O^2------>NO+H^2O

2NH^3+O^2----->2NO+3H^2O

2NH^3+O^2------>2NO+3H^2O

2NH^3+5/2 O^2------2NO+3H^2O

2NH^3+5/2 O^2------->2NO+3H^2O

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Yes, Alan and Faisyal are both correct. Two metals or objects can have the same outward structure but different masses. This is because of the way their atoms or particles are arranged. The way in which the particles of matter are arranged is called Density.

The degree of compactness of a substance is measured by its density. It is the amount of mass per unit volume that determines the degree of uniformity. It is the connection between a substance's mass and the quantity of space it takes up.

The density of a material is its mass per unit volume. The most common sign for density is ρ, however, the Latin letter D can also be used. Density is defined mathematically as mass divided by volume.

The formula for density is given as ρ= m/V, where is the density, m is the object's mass, and V is the object's volume. The density of an item is defined as its mass per unit volume. The kilogram per cubic meter (kg/m3) is the SI unit of density.

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If ammonia is added to the system, the reaction will shift to the right, in favour of the forward direction.

A reaction is said to be at equilibrium when the concentration of reactants is equal to the concentration of the products. This means that the rate at which reactants are forming products is equal to the rate at which products are changed back to reactants.

All reactions at equilibrium follow Le Chatelier's principle, which states that if a chemical system in equilibrium is disturbed by changing the conditions (such as concentration, temperature and pressure changes), the position of equilibrium shifts to the left or to the right in order to counteract the change and to re-establish an equilibrium.

This means that if certain factors in a chemical reaction at equilibrium is changed, the reaction will shift either to the left or to the right. If it shifts to the left, the backward reaction is favoured and more reactants are produces, but if it shifts to the right, the forward reaction is favoured, and more products are produced.

In the question above, ammonia (2NH₃) is added to the chemical system. This will cause an increase in the concentration of ammonia; hence, more ammonia will be converted to nitrogen and hydrogen in order to decrease the concentration of ammonia and re-establish equilibrium. This causes the reaction to shift to the right.

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Explanation:

When a virus infects a bacterial cell, often new viruses are assembled and released when the host bacterial cell is lysed. If these new viruses go on to infect new bacterial cells, the new host cells may not be lysed. What is the most plausible explanation for this?A) The bacterial cell must be resistant to infection by the virus.

B) The virus carries genes that confer resistance to the host bacterial cell.

C) The host bacterium couples the viral infection with transformation.

B) The virus carries genes that confer resistance to the host bacterial cell.

C) The host bacterium couples the viral infection with transformation.

Answer:

LCD TV's use a CCFL for backlighting

The group with a better result is group 1

Three ways that the groups could improve their results in terms of the crystallization experiment and the melting point investigation are: recrystallisation, elimination of impurity, and heating the solvent.

Group 1's result is better, it is so because they have got the melting point range in a close proximity, that means they do not have a broad range. Smaller the range of melting point, more accurate the compound is synthesized.

3 ways that the groups could improve their results:

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Taking into account the definition of enthalpy of a chemical reaction,  the value of ΔH for C + 3D → A + 2B is -157 kJ.

The enthalpy of a chemical reaction as the heat absorbed or released in a chemical reaction when it occurs at constant pressure. That is, the heat of reaction is the energy that is released or absorbed when chemicals are transformed into a chemical reaction.

A negative value of an enthalpy change indicates an exothermic reaction; a positive value of ΔH indicates an endothermic reaction.

Reversing the direction of a chemical equation changes the arithmetic sign of ΔH because a process that is endothermic in one direction is exothermic in the opposite direction.

In this case, the balanced reaction is:

A + 2B → C + 3D

and the enthalpy reaction ∆H° has a value of 157 kJ and it is an endothermic reaction.

To calculate the value of ΔH for C + 3D → A + 2B, you can see that the reaction is inverted, being in this case an exothermic reaction. Then, the enthalpy value must be reversed from sign.

Finally, the value of ΔH is -157 kJ.

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The correct statement in the process of balancing the equation is option C which is Do nothing, the equation is already balanced.

The chemical equation which is given in the question is -

CH₄ + O₂ → CO₂ + 2 H₂O

This reaction is a balanced chemical reaction as number of atoms of product and reactant are equal.

Number of carbon atoms on reactant side is 1 and number of carbon atoms on product side is also 1. Number of oxygen atoms on product side is 2 and hydrogen atoms is 4 and on reactant side, number of oxygen atom was 1 and number of hydrogen atom was 2 but after adding coefficient 2 in front of H₂O, number of Oxygen atoms became 2 and number of hydrogen atom became 4 making it a balanced reaction.

Therefore, correct option for process of balancing the equation is C.

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Answer:

128

Explanation:

Iron has atomic number of 53

so mass number is 53 + 75 = 128

The enthalpy of precipitation of calcium fluoride is -13.974 kJ/mol.

In order to solve this, first we need to write the balanced chemical reaction equation of the reaction in question:

CaCl₂(aq) + 2KF(aq) → CaF₂(s) + 2KCl(aq)

In order to calculate the enthalpy of precipitation (ΔH), we need the amount  of heat released (Q) and the number of moles of CaF₂ (n):

ΔH = Q/n

To calculate the number of moles, we can use the molarity (c = 1.00 M) of the calcium chloride solution and its volume (V = 25 mL = 0.025 L):

c = n/V ⇒ n = c*V

n = 1.00 M * 0.025 L = 0.025 mol

We calculate the amount of heat released (Q) using the following equation:

Q = (t₁ - t₂) * C * m

t₁ - initial temperature (25.0 ⁰C)

t₂ - final temperature (26.7 ⁰C)

C - specific heat capacity (4.184 J/⁰Cg)

m - the mass of the solution

We need the mass of the solution, which we can calculate using the density (d = 1.00 g/mL) and the volume (V = 25 mL + 25 mL = 50 mL) of the solution:

d = m/V ⇒ m = d*V

m = 1.00 g/mL * 50 mL = 50 g

Q = (25.0 ⁰C - 26.7 ⁰C) * 4.184 J/°Cg * 50 g

Q = -349.4 J

ΔH = -349.4 J / 0.025 mol

ΔH = -13974 J/mol = -13.974 kJ/mol

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Likely the foremost recognizable impact of soil disintegration is land degradation.

Asia-Pacific region is an area of extreme soil degradation.

Likely the foremost recognizable impact of soil disintegration is land debasement. As disintegration wears down the soil and its arrival, its capacity to bolster plant life diminishes.

Around the globe, soil disintegration is happening at a speedier rate than it can regenerate. When arrival corrupts, it annihilates territories and diminishes the sum of arrival accessible for agricultural needs or the requirements of natural life.

Since of land degradation, the soil cannot back plant life. Plants require solid, nutrient-filled soil to develop and deliver. In case the ground isn’t able to back vegetation, you won’t be able to develop nourishment.

Other than that, with fewer plants accessible to sequester carbon dioxide from the environment, the rate of climate alters increments. Increasingly carbon dioxide is cleared out within the climate, which is causing harm to the environment.

It increments the earth’s normal temperature and modifies precipitation, both of which can advance the progress of desertification.

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Answer: Hormones are are the body's chemical messengers, sending signals into the bloodstream and tissues. Hormones work slowly, over time, and affect many different processes, including growth and development, metabolism – how your body gets energy from the foods you eat- sexual function, reproduction, and mood

Answer:

Atomic Size Trend Across the Period

This is caused by the increase in the number of protons and electrons across a period. One proton has a greater effect than one electron cause of the coulombic law. Thus, electrons are pulled towards the nucleus, resulting in a smaller radius.

Explanation:

The volume of the system is found to be 5.097L and the % error is found to be 13.2%.

Every three-dimensional item requires some amount of space. The volume of this space is measured. Volume is defined as the space occupied by an item inside the confines of three-dimensional space. It is also known as the object's capacity. Volumes change depending on the form.

The absolute value of the difference between the measured and actual values is divided by the actual value and multiplied by 100 is the % error. Percent mistakes indicate the magnitude of your errors while measuring anything in an experiment. Smaller numbers of % error indicate that you are getting nearer to the acceptable or true value.

Given:

P = 12atm

n = 2 moles

T = 100℃ = 100 + 273 = 373K

To find:

(a) V = ?

(b) % error = ?

Formula:

PV = nRT

% error = (experimental – actual) / actual x 100

Calculations:

(a) V = nRT/P

V = 2 x 0.082 x 373 / 12

V = 5.097L

(b) % error = (5.097 – 4.5) / 4.5 x 100

% error = 0.597 / 4.5 x 100

% error = 0.132 x 100

% error = 13.2%

Result:

The system’s volume is 5.097L and the % error is 13.2%.

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Answer:

The alkali metals (Li, Na, K, Rb, Cs, and Fr) are the most reactive metals in the periodic table – they all react vigorously or even explosively with cold water, resulting in the displacement of hydrogen.

Explanation:

The metal that reacted most vigorously when placed in the acid is sodium, as it is an alkali metal.

At standard temperature and pressure, all of the bright, soft, extremely reactive alkali metals rapidly shed their outermost electron to create cations with charge +1.

One of the most reactive metals is the alkali metal. They have greater atomic radii and low ionization energies, which contribute to this. They have an oxidation state of 1, and they frequently give electrons during reactions. These metals stand out for their supple texture and silvery hue.

The alkali metals (Li, Na, K, Rb, Cs, and Fr) are the most reactive metals in the periodic table – they all react vigorously or even explosively with cold water, resulting in the displacement of hydrogen.

Therefore, the correct option is d. sodium.

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The question is incomplete. Your most probably complete question is given below:

Oxygen

magnesium

iron

sodium

For producing 639L of [tex]SF_6[/tex], a volume of 1916.96L of [tex]F_2[/tex] gas is required for the reaction.

If the pressure and temperature at which the reaction occurs is known, we may use the ideal gas law to compute the stoichiometry of processes involving gases by using the connection between the volume (in liters) and quantity of gases (in moles). A chemical reaction's volume of gas can be evaluated by collecting it in an inverted vessel filled with water. The gas pushes water out of the vessel, and the amount of liquid displaced is proportional to the amount or volume of gas.

Given:

Volume of [tex]SF_6[/tex] = 639L

Pressure, P = 2atm

Temperature, T = 273.15K

To find:

Volume, V of [tex]F_2[/tex] gas = ?

Formula:

PV = nRT

Calculations:

No. of moles of [tex]SF_6[/tex] = 2 x 639 / 0.082 x 273.15

No. of moles of [tex]SF_6[/tex] = 57.057 moles

[tex]S (s) + 3F_2 (g) \rightarrow SF_6 (g)[/tex]

From the reaction,

1 mole of [tex]SF_6[/tex] is formed from 3 moles of [tex]F_2[/tex]

Therefore,

No. of moles of [tex]F_2[/tex] = 3 x 57.057 = 171.171 moles

Volume of [tex]F_2[/tex] = 171.171 x 0.082 x 273.15 / 2

Volume of [tex]F_2[/tex] = 1916.96L

Result:

1916.96L of [tex]F_2[/tex] gas is required to produce 639L of [tex]SF_6[/tex].

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The molarity of a solution is 3.743M.

Molarity of a solution:

Molar concentration is a measure of the concentration of a chemical species, in particular of a solute in a solution, in terms of the amount of substance per unit volume of solution.

The formula for the molarity of a solution:

M = [tex]w_{B}[/tex] × 1000 / [tex]M_{B}[/tex] × V(ml)

[tex]w_{B}[/tex] = 50.54g

[tex]M_{B}[/tex] = molecular mass of water(H2O) = 2 + 16 = 18

V = Volume = 750ml

Putting the value in the equation, we get

M = 50.54 ×1000 / 18 × 750

   = 50540 / 13500

    = 3.743M

Therefore the molarity of a solution is 3.743M

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An unknown mixture is set in beaker on the teacher's table the five different parts of the mixture and we can separate it by method evaporation, distillation, sedimentation, and filtration

Mixture is the composed of one or more pure substances in varying compositions called as mixture and unknown mixture is separated by  shake the separatory funnel to allow intimate mixing of the solutions and effect extraction of the compound from the organic mixture and mixture can be physically separated by sedimentation process, filtration, crystallization, distillation, diffusion, panning, magnetic separation, and adsorption are a few of the methods used to separate materials and the substance is said to be pure when a sample of it has purified all other type of material

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Answer:0.74

Explanation:0.74

14.67KJ is the number of joules given off when 32.0 grams of steam cools from 110.0 C to ice at -40.0 C.

The vibrations of molecules or atoms increase when a body's temperature rises. From one area of the body to another, these vibrations are then transmitted. The amount of energy that a system's molecules vibrate with is referred to as its stored heat.

According to the definition of heat, it is the movement of energy from a warm item to a cooler one. The flow of heat energy is in the direction of moving from a substance with a higher temperature to one with a lower temperature.

q =mcΔT

    =32.0×4.18×(110-40)

    = 14.67KJ

Therefore, 14.67KJ is the number of joules given off when 32.0 grams of steam cools from 110.0 C to ice at -40.0 C.

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Answer:

c

Explanation:

ch4 + 4cuo --> CO2 + 2h20 + 4cu

Both the substrates as well the enzymes do not undergo denaturation since the enzyme was incubated with the substrate and it lost its activity.

When a certain substrate comes into contact with an enzyme, it will bind to the active region. Binding of the substrate to the active region of the protein results in the formation of a more stable enzyme substrate complex. This is because the enzyme substrate complex is more resistant to heat denaturation than just the enzyme.

Because the enzyme-substrate complex ground state has a lower energy level, more energy is required to overcome this energy barrier and denature the enzyme. In the question, it is given that 3% of the enzyme lost its activity, which might have happened when the enzyme and the substrate were incubated. Only 3% of the enzyme was liberated after the denaturation step, leaving 97% occupied with substrate.

As a result, neither the enzyme nor the substrate undergoes denaturation.

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The molar concentration of HCl in the original solution is 0.19

The balanced chemical equation for the reaction must be our starting point because it will provide us with the reactants' mole ratios and allow us to answer this question.

* NaOH + HCl --> NaCl + H2O

this means:

1 mole NaOH reacts with 1 mole HCl

thus the ratio of NaOH to HCl is 1: 1

Next we've got to calculate the moles of NaOH: (molecular Mass = 40 g/mol)

moles(NaOH) = 3.76g/40

= 0.094 moles

Now we can calculate the concentration of NaOH:

Note: 361mL/1000 = 0.361L

conc(NaOH) = 0.094 moles/0.361L

= 0.26 mol/L

Now the mole ratio of NaOH to HCl is 1:1

But we have used only 0.094 moles so since the ratio of NaOH to HCl is 1:1, it means that 0.094moles of NaOH can only react with 0.094 moles of HCl.

Note: 491mL/1000mL = 0.491L

conc(HCl) = 0.094 moles/0.491L

= 0.19 mol/L

Thus the molar concentration of HCl in the original solution is 0.19

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Answer:

what happened was when he dried off, there was still a little salt water on him. so, since the water has salt in it and the sun is very hot wich makes salty dried up as hard salt on him.

Continental drift is a geologic process that forms channel on Mars.

Continental drift, the same process that creates contemporary channels like the mid-Atlantic channel or the African Rift Valley, is the geologic process that is most likely to have created the channel on Mars. Massive troughs that are visible from orbit are being exposed when Mars' tectonic plates separate. Similar to Earth, Mars too experiences gradual continental drift, which moves by less than an inch per year and is much too slow for any person to notice. However, this can lead to significant geological and geographic changes over millions of years that modify the planet's surface.

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In the diagnosis of cystic fibrosis caused by gene mutation, the mass of AgCl formed and the mass of [tex]Cl^-[/tex] remaining are 0.003583g and 0.006203g respectively, and the % of [tex]Cl^-[/tex] precipitated is 12.5%.

Cystic fibrosis (CF) is a hereditary condition that causes respiratory and gastrointestinal issues. An alteration (mutation) in the gene that produces the cystic fibrosis transmembrane regulator (CFTR) protein causes cystic fibrosis. To be born with CF, a new born must get two copies of the CF gene, one from each parent.

Cystic fibrosis causes thick, sticky mucus to accumulate in the lungs. CF causes recurring lung infections and makes breathing difficult over time. Other organs of the body, like the pancreas, might be affected by Cystic fibrosis, making it difficult to digest meals and maintain a healthy weight.

a) Mass of AgCl precipitate = no. of moles x molecular mass

Mass = 0.025mol/L x 0.001L x 143.32g/mol

Mass = 0.003583g

b) Mass of [tex]Cl^-[/tex] remaining in solution after precipitation = no. of moles x molecular mass

No. of moles of [tex]Cl^-[/tex] = 0.2mol/L x 0.001L = 0.0002 mol

No. of moles of [tex]Ag^+[/tex] = 0.25mol/L x 0.001L = 0.000025 mol

Mass of [tex]Cl^-[/tex] remaining = (0.0002 – 0.000025) x 35.45

Mass of [tex]Cl^-[/tex] remaining = 0.006203g

c) % of [tex]Cl^-[/tex] precipitated = 0.000025 / 0.0002 x 100 = 12.5%

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In this question, we need to find the value of pressure of a 15 grams sample of CO2 gas, and in order to find this value, we will be using the Ideal gas law formula, which is the following:

PV = nRT

Where:

P = pressure in atm

V = volume in liters, 20 Liters

n = number of moles

R = gas constant, 0.082

T = temperature in kelvin, 0°C = 273 K

The number of moles we need to find based on the mass in the question and based on the molar mass of CO2, 44g/mol:

44g = 1 mol

15g = x moles

44x = 15

x = 15/44

x = 0.34 moles of CO2 in 15 grams

Now we have the values to add to the formula:

P * 20 = 0.34 * 0.082 * 273

20P = 7.61

P = 7.61/20

P = 0.38 atm of pressure

The pressure will be 0.38 atm