The metals in Groups 1A, 2A, and 3A ____.
A) all have ions with a 1+ charge c. all form ions with a negative charge
b. gain electrons when they form ions d. lose electrons when they form ions

The enthalpy for the decomposition of one mole of [tex]{\text{MgO}}[/tex] is  [tex]\boxed{602\;{\text{kJ}}}[/tex].

Further Explanation:

This problem is based upon Hess’s Law. Hess’s law is utilized for calculating the enthalpy change of a reaction that can be obtained simply by summation of two or more reactions. In accordance with the Hess’s law, [tex]\Delta H[/tex] of an overall reaction is obtained by adding the enthalpy change for each individual step reaction involved to obtain the overall reaction.

[tex]\boxed{\Delta\text{H}_{\text{overallrxn}}=\Delta\text{H}_{1}+\Delta\text{H}_{2}+......+\Delta\text{H}_{n}}[/tex]

Enthalpy is defined as state function and therefore its value depends upon the initial and final state of system but not upon the path. This is the reason that the overall reaction can be simply obtained by adding or subtracting the enthalpy change of the individual steps utilized to get the final reaction.

1. Combination reactions:

These reactions are also known as synthesis reaction. These are the reaction in which two or more reactants combine to form single product. These are generally accompanied by the release of heat so they are exothermic reactions.

Examples of combination reactions are as follows:

(a) [tex]{\text{Ba}} + {{\text{F}}_2}\to{\text{Ba}}{{\text{F}}_2}[/tex]

(b) [tex]{\text{CaO}}+{{\text{H}}_2}{\text{O}} \to{\text{Ca}}{\left( {{\text{OH}}} \right)_2}[/tex]

2. Decomposition reactions:

The opposite of combination reactions is called as decomposition reaction. Here, a single reactant gets broken into two or more products. Such reactions are usually endothermic because energy is required to break the existing bonds between the reactant molecules.

Examples of decomposition reactions are as follows:

(a) [tex]2{{\text{H}}_2}{{\text{O}}_2}\to2{{\text{H}}_2}{\text{O}}+{{\text{O}}_2}[/tex]

(b) [tex]2{\text{NaCl}}\to{\text{2Na+C}}{{\text{l}}_2}[/tex]

The combination reaction for the formation of [tex]{\text{MgO}}[/tex] is as follows:

[tex]{\text{2Mg}}\left(s\right)+{{\text{O}}_2}\left(g\right)\to2{\text{MgO}}\left(s\right)[/tex]

The value of [tex]\Delta {H_1}[/tex] is [tex]180.7{\text{ kJ}}[/tex].

Step 1: The enthalpy change of the following reaction is [tex]\Delta {H_1}[/tex] .

[tex]{\text{2Mg}}\left(s\right)+{{\text{O}}_2}\left(g\right)\to2{\text{MgO}}\left(s\right)[/tex]    ......(1)

The decomposition reaction of [tex]{\text{MgO}}[/tex] is as follows:

[tex]2{\text{MgO}}\left(s\right)\to{\text{2Mg}}\left(s\right)+{{\text{O}}_2}\left(g\right)[/tex]

Step 2: The enthalpy change of the following reaction is [tex]\Delta {H_2}[/tex].

[tex]2{\text{MgO}}\left(s\right) \to{\text{2Mg}}\left(s\right)+{{\text{O}}_2}\left(g\right)[/tex]                                              ......(2)

The reaction (2) can be obtained by reversing the reaction (1) so the value of [tex]\Delta {H_2}[/tex] can be obtained as follows:

[tex]\begin{aligned}\Delta {H_2}&=-\Delta {H_1}\\&=-\left({-1204\;{\text{kJ}}}\right)\\&=1204\;{\text{kJ}}\\\end{aligned}[/tex]

In the decomposition reaction,two moles of [tex]{\mathbf{MgO}}[/tex]  dissociates to give two moles of [tex]{\mathbf{Mg}}[/tex] and one mole of [tex]{{\mathbf{O}}_{\mathbf{2}}}[/tex] and therefore the enthalpy for the decomposition of one mole of  is as follows:

[tex]\begin{aligned}{\text{Enthalpy for decomposition of 1 mole}}&=\frac{{\Delta {H_2}}}{2}\\&=\frac{{1204\;{\text{kJ}}}}{2}\\&=602\;{\text{kJ}}\\\end{aligned}[/tex]

Hence, enthalpy for decomposition of one mole of [tex]{\mathbf{MgO}}[/tex] is [tex]{\mathbf{602}}\;{\mathbf{kJ}}[/tex].

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Answer details:

Grade: Senior school

Subject: Chemistry

Chapter: Thermodynamics

Keywords: Hess’s Law, enthalpy, MgO, O2, Mg, 1204 kj, -1204 kj, 602 kj , -602 kj overall reaction, adding, state function, initial state, and final state.

The heat required to decompose 1 mole of MgO is 602 kJ/mol.

The equation of the reaction is;

2Mg(s) + O2(g) → 2MgO(s) ΔH=−1204 kJ

The equation as written is called a thermochemical equation. It shows the amount of energy lost or gained in a reaction.

We can write the equation for the decomposition of MgO as follows;

2MgO(s) → 2Mg(s) + O2(g) ΔH= 1204 kJ

Recall that energy is absorbed to decompose MgO hence ΔH is positive.

From the stoichiometry of the reaction;

2 moles of MgO requires 1204 kJ of heat

1 mole of MgO requires 1 mole ×  1204 kJ/2 moles

= 602 kJ/mol

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Answer:

0

Explanation:

Calcium sulfide has molecular formula CaS. Calcium is a metal of group 2, and sulfur, a nonmetal of group 6, and they form an ionic compound, not a molecule.

So, calcium will give 2 electrons to sulfur, so both of them will have 8 electrons in their valence shell. All these electrons will be in pairs, so there will be 0 lone pairs of electrons.

Each materials have a specific density. In general, the density of liquids are less as compared to the solids whereas the gases are less dense as compared to liquids. Here the density of 'Kr' gas at STP is 3.7386 g / L.

The density is the measurement of how tightly a material is packed together. It can also be defined as the ratio of the mass to the volume. It is a unique property of a particular object. Its SI unit is kg / m³.

The equation used to calculate the density is:

Density = Mass / Volume

Mass of Krypton = 83.798 g

The volume occupied any gas at STP (Standard temperature and pressure) is 22.414 L.

Then the density is:

Density = 83.798 / 22.414

= 3.7386 g / L

Thus the density of krypton gas is 3.7386 g / L.

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Answer : (C) The heat of fusion for water is the amount of energy needed for water to melt.

Explanation :

Heat of fusion : It is calculate the amount of energy required for melting of a substance to change its states from solid to liquid at constant pressure.

Fusion is a process in which phase changes from solid to liquid.

In case of water, the solid ice converted into liquid water by the process of melting.

The reaction of phase changes in water is,

[tex]Ice(s)\overset{Fusion}{\rightarrow} Water(l)[/tex]

The nucleus of an atom is the central core and is composed of protons and neutrons.

The nuclei of most atoms usually have more neutrons than protons.

The nuclei are dense, but they are positively charged because of the protons.

the central core and is composed of protons and neutrons

neucleus is positivly charged and protons are either equal or less then nuetrons

molecular formula is the acutal composition of the components making up the compound

chlorophyll a molecular formula is - C₅₅H₇₂MgN₄O₅

so we have to find how many atoms are in 1 molecule

for this we have to add all the atoms of each element making up this 1 molecule

number of atoms of each element

C - 55

H - 72

Mg - 1

N - 4

O - 5

the sum of all the atoms - 55 + 72 + 1 + 4 + 6 = 138

answer is C ) 138

In the first voltaic cell, a salt bridge was used for ion flow between CuSO4 and ZnSO4 solutions. The salt bridge ensured electrical neutrality within the circuit and allowed for ion exchange to maintain cell function.

In the first voltaic cell, a salt bridge was used to allow for ion flow between the solutions of CuSO4 and ZnSO4.

The purpose of the salt bridge is not only to maintain electrical neutrality within the internal circuit, but is also to permit the exchange of ions (transfer of charge). Without the salt bridge, the solution would rapidly reach the point where they could no longer release or accept ions, causing the voltaic cell to stop working.

The device, therefore, significantly enhanced the effectiveness and longevity of voltaic cells, playing an integral role in the advancement of electrochemistry.

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Explanation:

[tex]3CO(g)+Fe_2O_3(s)\rightarrow 2Fe(s)+3CO_2(g)[/tex]

1)Mass of CO when 210.3 g of Fe produced.

Number of moles of [tex]Fe[/tex] in 210.3 g=

[tex]\frac{\text{Given mass of Fe}}{\text{Molar mass of Fe}}[/tex]

[tex]=\frac{210.3}{55.84 g/mol}=3.76 mol[/tex]

According to reaction, 2 moles of Fe are obtained from 3 moles of CO, then 3.76 moles of Fe will be obtained from : [tex]\frac{3}{2}\times 3.76 moles[/tex] of CO that is 5.64 moles.

Mass of CO in 5.64 moles =

[tex]\text{Number of moles}\times \text{molar mass of CO}=5.46\times 28 g/mol=157.92 g[/tex]

2)Mass of CO when 209.7 g of Fe produced.

Number of moles of [tex]Fe[/tex] in 209.7 g=

[tex]\frac{\text{Given mass of Fe}}{\text{Molar mass of Fe}}[/tex]

[tex]=\frac{209.7}{55.84 g/mol}=3.75 mol[/tex]

According to reaction, 2 moles of Fe are obtained from 3 moles of CO, then 3.75 moles of Fe will be obtained from : [tex]\frac{3}{2}\times 3.75 moles[/tex] of CO that is 5.625 moles.

Mass of CO in 5.625 moles =

[tex]\text{Number of moles}\times \text{molar mass of CO}=5.625\times 28 g/mol=157.5 g[/tex]

Answer:

5.625 moles. took the test

The diatomic species C2^2+ is diamagnetic, while the species Li2- and B2^2- are paramagnetic due to the presence of unpaired electrons.

In chemistry, a species is paramagnetic if it has at least one unpaired electron and is diamagnetic if it has no unpaired electrons. Here, we can determine these characteristics by filling out molecular orbital diagrams and checking for unpaired electrons.

For C2^2+, two electrons are removed, making this molecule diamagnetic with no unpaired electrons. Li2- gains an electron, so it becomes paramagnetic with one unpaired electron. B2^2- gains two electrons, but it still remains paramagnetic because these two gained electrons will not pair up.

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If an object is only partially submerged in a fluid, the correct statement is; The volume of the displaced fluid equals the volume of the object. Option A is correct.

This statement is known as Archimedes' principle. According to this principle, when an object is immersed or partially submerged in a fluid, it experiences an upward buoyant force equal to the weight of the fluid it displaces. The volume of the displaced fluid will be equal to the volume of submerged portion of the object.

"The density of the fluid equals the density of the object" is not necessarily true. The density of the fluid and the object can be different, and it does not directly determine the behavior of a partially submerged object.

The density of the fluid is greater than the density of the object" and "The density of the fluid is less than the density of the object" are not universally true statements. The density comparison between the fluid and the object does not determine the behavior of a partially submerged object. It depends on the relative densities and the shape of the object.

Hence, A. is the correct option.

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The atomic number and ionic radius increase down Group 2A, while the first ionization energy decreases. These relationships are consistent with periodic trends seen in other groups.

The relationship between atomic numbers and ionic radii in the Group 2A elements, also known as the alkaline earth metals, follows a general trend. As you move from top to bottom within the group, the atomic number increases and so does the ionic radius. This is because the number of energy levels or shells occupied by electrons increases down the group, resulting in larger atomic and ionic radii.

The relationship between atomic numbers and first ionization energies in the Group 2A elements is an inverse relationship. As the atomic number increases from top to bottom within the group, the first ionization energy generally decreases. This is because the increasing number of energy levels provides greater shielding of the outermost electrons from the positively charged nucleus, making it easier to remove an electron and requiring less energy.

These relationships are consistent with the periodic trends observed in other groups of elements as well. In general, atomic and ionic radii increase from top to bottom within a group, and first ionization energies decrease. These trends can be explained by the increasing number of energy levels/shells as you move down a group, which affects the size and attractions between the electrons and nucleus.

Answer:

The volume occupied by the gas at pressure 970 torr is 91.08 mL.

Explanation:

To calculate the new pressure, we use the equation given by Boyle's law.

This law states that pressure is directly proportional to the volume of the gas at constant temperature.  

The equation given by this law is:

[tex]P_1V_1=P_2V_2[/tex]  (at constant temperature)

where,

[tex]P_1\text{ and }V_1[/tex] are initial pressure and volume.

[tex]P_2\text{ and }V_2[/tex] are final pressure and volume.

We are given:

[tex]P_1=930 Torr\\V_1=95 mL\\P_2=970 Torr\\V_2=?[/tex]

Putting values in above equation, we get:

[tex]930 Torr\times 95 mL=270 Torr \times V_2\\\\V_2=\frac{P_1V_1}{P_2}=\frac{930 Torr\times 95 mL}{270 Torr}=91.08 mL[/tex]

The volume occupied by the gas at pressure 970 torr is 91.08 mL.

Electronegativity measures an atom's ability to attract electrons. In covalent bonding, the electrons are shared between two atoms. However, if one atom is more electronegative, it will attract more shared electrons, potentially creating a polar covalent bond.

Electronegativity is a measure of the ability of an atom in a chemical compound to attract electrons. In covalent bonding, the electrons are shared between two atoms. However, these electrons are not always shared equally. If one atom has a higher electronegativity than the other, it will pull the shared electrons closer to itself. This can result in a polar covalent bond, where one side of the molecule carries a slight negative charge and the other side carries a slight positive charge. For example, in a water molecule (H2O), the electronegativity of oxygen is higher than that of hydrogen, leading oxygen to attract more electrons and making the bond a polar covalent bond.

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It will be nitrogen.

The energy associated with the formation of 1 mol of gaseous cations is The ionization energy. 1 mole of electrons will form 1 mole of gaseous atoms under standard conditions. The ionization energy decreases as you go down a group on the periodic table.

Explanation:

Ionization energy is defined as the energy required to remove the most loosely bound electron from a neutral gaseous atom.

With increase in atomic number there will also occur an increase in atomic size of the atom. As a result, there will be less force of attraction between the nucleus and the valence electrons of the atom.

Hence, it is easy to remove the most loosely bound electron. Therefore, with increase in size there will occur a decrease in the size of atom.

Since, out of the given group 5A elements, arsenic is larger in size and nitrogen is the smallest. Therefore, ionization energy for nitrogen will be the highest.

Thus, we can conclude that nitrogen is the element which has the highest ionization energy.

Answer:

A. acid

Explanation:

If youve ever heard the term, hydrochlori acid, then you would know it is an acid. Since it has a ph level lower than 7 it is considered an acid, due to the fact that a base woul dbe higher than 7 and neutral would be 7. Hope this helps!

Final answer:

When analyzing the reaction A + 3B \(\rightarrow\) 4C with 3.0 moles of A and 6.0 moles of B, B becomes the limiting reactant because it is not present in sufficient quantity to fully react with A, leaving some A unreacted.

Explanation:

Given the equation A + 3B \(\rightarrow\) 4C, we are dealing with a stoichiometry problem where 3.0 moles of A is reacted with 6.0 moles of B. To determine which reactant is leftover, we analyze the stoichiometric relationships. According to the equation, for every mole of A, we need 3 moles of B to completely react. For 3.0 moles of A, 9.0 moles of B would be required. Since only 6.0 moles of B are available, B becomes the limiting reactant. Consequently, some amount of A will not react and will be left over.

Therefore, choice a is incorrect because it misinterprets the stoichiometry required for A. Choice b is incorrect as it confuses the product formation with the reactant consumption. Choice c and choice e are incorrect because B, not having more moles than required, cannot be leftover or support a scenario where neither reactant is leftover. Choice d is the correct choice, as it accurately reflects the stoichiometric relationship that 3 moles of B react with every 1 mole of A, making B the limiting reactant due to its insufficient quantity to react with all of A provided.

Answer : The mass of [tex]CO_2[/tex] produced will be, 6.16 grams.

Explanation : Given,

Mass of [tex]CaCO_3[/tex] = 14 g

Mass of [tex]HCl[/tex] = 56.70 g

Molar mass of [tex]CaCO_3[/tex] = 100 g/mole

Molar mass of [tex]HCl[/tex] = 36.5 g/mole

Molar mass of [tex]CO_2[/tex] = 44 g/mole

First we have to calculate the moles of [tex]CaCO_3[/tex] and [tex]HCl[/tex].

[tex]\text{Moles of }CaCO_3=\frac{\text{Mass of }CaCO_3}{\text{Molar mass of }CaCO_3}=\frac{14g}{100g/mole}=0.14moles[/tex]

[tex]\text{Moles of }HCl=\frac{\text{Mass of }HCl}{\text{Molar mass of }HCl}=\frac{56.70g}{36.5g/mole}=1.55moles[/tex]

Now we have to calculate the limiting and excess reagent.

The balanced chemical reaction is,

[tex]CaCO_3(s)+2HCl(aq)\rightarrow CO_2(g)+H_2O(l)+CaCl_2(aq)[/tex]

From the balanced reaction we conclude that

As, 1 moles of [tex]CaCO_3[/tex] react with 2 mole of [tex]HCl[/tex]

So, 0.14 moles of [tex]CaCO_3[/tex] react with [tex]0.14\times 2=0.28[/tex] moles of [tex]HCl[/tex]

From this we conclude that, [tex]HCl[/tex] is an excess reagent because the given moles are greater than the required moles and [tex]CaCO_3[/tex] is a limiting reagent and it limits the formation of product.

Now we have to calculate the moles of [tex]CO_2[/tex].

As, 1 moles of [tex]CaCO_3[/tex] react to give 1 moles of [tex]CO_2[/tex]

So, 0.14 moles of [tex]CaCO_3[/tex] react to give 0.14 moles of [tex]CO_2[/tex]

Now we have to calculate the mass of [tex]CO_2[/tex].

[tex]\text{Mass of }CO_2=\text{Moles of }CO_2\times \text{Molar mass of }CO_2[/tex]

[tex]\text{Mass of }CO_2=(0.14mole)\times (44g/mole)=6.16g[/tex]

Therefore, the mass of [tex]CO_2[/tex] produced will be, 6.16 grams.

The mass of CO2 produced in the reaction is 5.74 g.

To calculate the mass of CO2 produced in the reaction, we need to determine the change in mass caused by the formation of CO2. We start with the mass of CaCO3 (14.00 g) and the mass of HCl solution (56.70 g). The total mass of the reactants is the sum of these two: 14.00 g + 56.70 g = 70.70 g.

The mass of the resulting solution is 64.96 g, so the change in mass is 70.70 g - 64.96 g = 5.74 g. This change in mass corresponds to the mass of CO2 produced in the reaction, so the mass of CO2 is 5.74 g.

Final answer:

When you smell an onion being cut in the kitchen, it is because of a process called diffusion. The molecules of the onion's odor travel through the air and reach your nose, where they bind to olfactory receptors and send signals to your brain. Other substances that can be detected through smell also exhibit this diffusion behavior.

Explanation:

When you walk into your house and smell the onion being cut in the kitchen, you are able to smell it because of a process called diffusion. Diffusion is the net movement of particles from an area of greater concentration to an area of lesser concentration. The particles of the onion's odor travel through the air and reach your nose, where they bind to specialized olfactory receptors in your olfactory epithelium. These receptors send signals to your brain, allowing you to perceive the smell of the onion.

Other substances that exhibit this behavior and can be detected through your sense of smell include various gases, volatile compounds, and particulate matter. For example, the smell of coffee, flowers, or gasoline are all due to molecules in the air that reach your olfactory receptors through diffusion.