The ​\( pK_a \)​ is a measure of the strength of acids and the higher value means the weaker acid. According to the value of ​\( pK_a \)​, ​\( HClO_3 \)​ is the Strong acid and completely dissociate in aq solution.

The acid and base equivalence point is a point at which the moles of the titrant and analyte are equal. The first equivalence point of H₃PO₄ corresponds to the conversion of H₃PO₄ to H₂PO₄^–  Ka1and the second equivalence point corresponds to the conversion of H₂PO₄^– to HPO₄ ^2- Ka2and the third equivalence point corresponds to the conversion HPO₄^2- to PO₄^3-. Ka3

The acid with the strongest conjugate base will be the weakest acid of the group. According to the value of pK_a, HCN is the only weak acid listed among the choices.

Formaldehyde is a polar compound. One end of the molecule has slightly positive charge. The other end has lightly negative charge.
Carbon dioxide in a non-polar compound. Both end of the molecule are slightly negative in charge.

As can be seen, the BH3 bond angle will be 120 degrees since it has a trigonal planar molecular geometry.

In chemistry, an ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. Ionic Solids are solids composed of oppositely charged ions. They consist of positively charged cations and negatively charged anions .When Ionic Solids are dissolved in water the cations and the anions separate, they become free to move about in the water allowing the solution to conduct electrical current.
For cesium chloride, you could draw a simple diagram showing the arrangement of the chloride ions around each cesium ion.

The above mentioned content is applied about MgBr2 too.

The equilibrium constant is calculated by the equation below

K_c = [SO₃]² / [SO₂]² [O₂]

Kc= [0.077]²/ [0.077]² [0.087]    Kc= 1.15

we must first calculate the [OH¯]. To do this, we will use the pH and acid base concepts. Then, we will use the K_sp expression to calculate the K_sp

Using pOH = -log ₁₀ ([OH^–])    pH + pOH = 14.0

pOH = (14.0 – 5.0) = 9.0 and [OH^–] = 1× 10-9 M

The solubility equilibrium and product are

Fe(OH)₃(s)⇌ Fe³⁺(aq) + 3OH^–(aq)   K_sp = [Fe3⁺][OH^–]³

​\( [Fe^{3+}] =\frac{[Ksp]}{[OH-]3}= 4 \times 10^{-38}/( 1\times 10^{-9})^3  = 4×10^{-11} M \)​

\[ R_{NO2}=\frac{(9.2/46 mol)}{(80/60 min)}=0.15mole.min^{(-1)} \]

The unit for K is M^-1 S^-1, so the rate of the reaction is calculated according to the equation below: Rate= K [A]². The overall reaction is a second-order reaction.

\[ 50 ml \times \frac{0.1mol}{1lit} \times \frac{1lit}{1000ml} \times \frac{100gr}{37 gr} \times \frac{37 gr}{1 mol} \times \frac{1ml}{1.18gr}= 0.42 ml \]

A solution is a special type of homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. The mixing process of a solution happens at a scale where the effects of chemical polarity are involved, resulting in interactions that are specific to solvation. The solution assumes the phase of the solvent when the solvent is the larger fraction of the mixture, as is commonly the case. The concentration of a solute in a solution is the mass of that solute expressed as a percentage of the mass of the whole solution. The term aqueous solution is when one of the solvents is water.

\[ NO_3^{-1}=\frac{0.25 \text{ mol } KNO3}{L} \times \frac{1 { \text{ mol }} NO3^{-1}}{\text{mol }KNO3}=0.25 \text{ M} \]

\[ NO_3^{-1}=\frac{0.10 \text{ mol Al} (NO3)3}{L} \times \frac{3 { \text{ mol }} NO3^{-1}}{\text{mol Al }(NO3)3}=0.30 \text{ M} \]

\[ NO_3^{-1}=\frac{0.20 \text{ mol Ca} (NO3)2}{L} \times \frac{2 { \text{ mol }} NO3^{-1}}{\text{mol Ca }(NO3)2}=0.40 \text{ M} \]

The pressure of an ideal gas can be calculated by the equation below

PV= nRT

At first, we have to convert 25⁰C to kelvin   T= 25.0 + 273= 298 K

V= 2.50 l  , n= 0.50 mol  , ​\( R= 0.0821 \frac{l\text { } atm}{mol\text { } K} \)​

\[ P=\frac{n RT}{V}=\frac{0.50mol \times 0.0821 \frac{l\text { } atm}{mol\text { } K} \times 298K}{2.50l}=4.89 \]

Rounding off 4.89 to 4.9 atm.

The pressure of a gas is inversely proportional to its volume when the temperature is constant. If the temperature of a system remains the same over a given time. It is used in Boyle’s law

P₁V₁= P₂V₂

P₁ and V₁=initial pressure and volume

P₂ and V₂= final pressure and volume

0.8(atm) × 1.5 (l) = 1.6 (atm) × X (l) X= 0.75 l

Metals have fewer electrons in their outer shell compared to non-metals and hence in reactions, they give away their outermost electrons to the non-metals, as it is easier to get rid of few electrons than many. As we work our way down group 2, each successive element has an increasing number of shells and hence an increased atomic radius, so the outermost electrons experience less attraction to the nucleus and can be transferred to the non-metal element more easily.

Flask is commonly used for containing liquid and performing mixing, heating, cooling, precipitation, condensation, and other processes.

The stability of phases can be predicted by the chemical potential, in that the most stable form of the substance will have the minimum chemical potential at the given temperature and pressure. This can be summarized in a phase diagram like the one shown below.

By decreasing the covalent property of ionic composition, the experimental value of lattice energy will be more. It has more difference with its measured value because the covalent property of CsF is less than the others. Therefore we can expect that the lattice energy of CsF is higher than the others.

All nuclear reactions must be balanced in mass number and atomic number. To balance the equation above for mass, charge, and mass number, the second nucleus on the right side must have atomic number 0 and mass number -1; it is therefore also ⁰_-1e.

Reduction potential (E_h) is the measurement of the tendency of an environment to oxidize substrates. Strong reducing agents can be said to have high electron-transfer potential. Therefore Li is the strongest reducing agent.

Fig. An electrolytic cell

An electrolytic cell is an electrochemical cell that drives a non-spontaneous redox reaction through the application of electrical energy. They are often used to decompose chemical compounds.

Galvanic cells compared to electrolytic cells:
In an electrolytic cell, the current is passed through the cell by an external voltage, causing an otherwise nonspontaneous chemical reaction to proceed. In a galvanic cell, the progress of a spontaneous chemical reaction causes an electric current to flow. An equilibrium electrochemical cell is at the state between an electrolytic cell and a galvanic cell. The tendency of a spontaneous reaction to push a current through the external circuit is exactly balanced by an external voltage that is called a counter electromotive force or counter e.m.f. so that no current flows. If this counter voltage is increased the cell becomes an electrolytic cell and if it is decreased the cell becomes a galvanic cell.

When Mendeleev’s table is ordered by the atomic number, the discrepancies within this table disappear. Tellurium has an atomic number of 52, while iodine has an atomic number of 53. So even though tellurium does indeed have a greater atomic mass than iodine, it is properly placed before iodine in the periodic table. Mendeleev and Moseley are credited with being most responsible for the modern periodic law: when elements are arranged in order of increasing atomic number, there is a periodic repetition of their chemical and physical properties. The result is the periodic table as we know it today. Each new horizontal row of the periodic table corresponds to the beginning of a new period because a new principal energy level is being filled with electrons. Elements with similar chemical properties appear at regular intervals, within the vertical columns called groups.

Electronegativities generally increase from left to right across a period. This is due to an increase in nuclear charge. Alkali metals have the lowest electronegativities, while halogens have the highest. Because most noble gases do not form compounds, they do not have electronegativities. Note that there is little variation among the transition metals. Electronegativities generally decrease from top to bottom within a group due to the larger atomic size.

\[ \text{mol }Na=\frac{2.82 \text{ g }Na}{23 \text{ g }/mol}=0.1226 \]

\[ \text{mol }Cl=\frac{4.35 \text{ g }Cl}{35.45 \text{ g }/mol}=0.1227 \]

\[ \text{mol }O=\frac{7.83 \text{ g }O}{16 \text{ g }/mol}=0.4894 \]

We should divide the numbers above by the lowest number of moles.

\[ \text{ for } Na=\frac{0.1226}{0.1226}=1 \\ \text{ for } Cl=\frac{0.1227}{0.1226} \approx 1 \\ \text{ for } O=\frac{0.4894}{0.1226}=4 \]

The empirical formula is NaClO₄

\[ \text{ mass of }X =\text{ mass of oxygen } \times \frac{1}{\text{ molar mass of O }} \times \frac{\text{ 2 mol X} }{\text{ 3 mol O}} \times \text{molar mass of X} \]

We should substitute 3.625 g for mass of X and 1.476 g for mass of O

\[ 3.625 g = 1.476 g × \frac{1}{16 g/mol} × 2/3 × \text{ molar mass of X } \\ \text{ Molar mass } X \approx 59 \]

We start with a 100-g sample.

We divide each element’s percentage (converted to grams) by its atomic mass:

\[ C:\frac{92.3 g}{12g/mol}=7.69 \\ H:\frac{7.7 g}{1g/mol}=7.7 \]

To establish a whole-number ratio of carbon to hydrogen, divide each factor by the smallest factor. The ration of atoms is 1 to 1

\[ C:\frac{7.69}{7.69}=1 \\ H:\frac{7.7}{7.69}\approx 1 \]

The empirical formula is CH. Since the molecular mass of the compound is 78.1 amu, the sum of the mass of 1C and 1H in atomic mass units (12amu + 1amu = 13amu) must be equal to 78.1 amu. To find this number, divide 78.1 amu by 13 amu:

​\( \frac{78.1}{13}=6 \text{ so the molecular formula is }C_6H_6 \)​

The enthalpy of formation (or heat of formation) ∆H_f is the enthalpy change associated with forming 1 mole of NO₂   from its constituent elements in their standard state

NO (g) + O (g) → NO₂(g)

We can use Hess’s law to calculate the heat of formation of NO_2.

The law says: if a reaction is carried out in a number of steps, ∆H for the overall reaction is the sum of ∆H for each individual step. We want NO2 on the product side, so we reverse the second reaction. The sign of ΔH is also changed. The third reaction multiply ½

NO _(g) + O_{3 (g)} → NO_{2 (g)} + O_{2 (g)}          ∆H = -198.9 kJ

3/2 O_{2 (g)} → O_{3 (g)}                               ∆H = +142.3 kJ

O _(g) → ½ O_{2 (g)}                                 ∆H = -495.0/2 = -247.5 kJ

overall      NO _(g) + O _(g) → NO_{2 (g)}

∆H = (-198.9) + 142.3 -274.5 = -304.1 kJ

Entropy is roughly related to the disorder, and gases are more disordered than the other states.

Reaction 1: The number of particles in the system decreases, i.e. there are four moles of gas reactants and only 2 moles of gas products.so the entropy is on the decline.

Reaction 2: The number of particles in the system increases, i.e. the single reactant dissociates into two ion particles.  In addition, the ions in the ionic solid are organized in a rigid lattice structure whereas the ions in aqueous solutions are free to move randomly through the solvent. So the entropy is in a decrease.

The number of particles in the system increases. i.e. there is one mol of gas reactant and 2 moles of gas products. The disorder is increased more.