Hydrofluoric acid, hf(aq), cannot be stored in glass bottles because compounds called silicates in the glass are attacked by the hf(aq). sodium silicate (na2sio3), for example, reacts as shown below. na2sio3(s) + 8 hf(aq) h2sif6(aq) + 2 naf(aq) + 3 h2o(l) (a) how many moles of hf are needed to react with 0.340 mol of na2sio3?

In a controlled experiment, the factor tested is called the [tex]\boxed{{\text{B}}{\text{. independent variable}}}[/tex].

Further Explanation:

A procedure that is performed in order to support, disprove or validate a hypothesis is known as an experiment. A hypothesis is an idea or thought that needs to be tested with the help of experiments.

Types of experiments:

1. Controlled experiments

The type of experiment that is used for comparing the results of experimental samples with the control samples is called a controlled experiment. Such experiments involve a drug trial. The experimental group will be the one that receives the drug and the other one receiving regular treatment will be the controlled group. The experimental group is also known as the treatment group. Another example of controlled experiments is the protein assay.

2. Natural experiments

These are also called quasi-experiments. These are performed by exposing individuals to the conditions that are governed by nature. Experiments involving weather changes and natural disasters are examples of natural experiments.

3. Field experiments

These are quite different from the experiments performed in the laboratory. Such experiments are usually performed in social studies. These have higher external validity as compared to normal lab experiments. Economic analysis of health and education are some examples of such experiments.

The variable that can be changed by the investigator is called the independent variable while the variable is the one that is affected by the changes in experimental conditions. All the variables in a controlled experiment are kept constant; except for the factor that is to be tested. Such a factor is called the independent variable or the experimental variable.

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Answer Details:

Grade: Senior School

Chapter: Keys to studying chemistry

Subject: Chemistry

Keywords: experiment, hypothesis, controlled experiment, natural experiment, field experiments, dependent variable, independent variable, quasi-experiments.

I believe the correct volume of 0.212 M NaOH is 25.0 mL and not 0 mL.

Since the reactants are strong base and a strong acid then this is an example of neutralization reaction. The balance chemical reaction is:

NaOH + HCl ---> NaCl + H2O

We can see from the reaction above that the ratio of NaOH to HCl is 1:1. Therefore,

number of moles HCl = (0.212 mol NaOH / L) * 0.025 L * (1 mol HCl / 1 mol NaOH)

number of moles HCl = 0.0053 mol HCl

Molarity is number of moles divided by volume in Liters, therefore the molarity of HCl solution is:

Molarity HCl = 0.0053 mol HCl / 0.0136 L

Molarity HCl = 0.390 M

The electron lost to form a potassium ion from a potassium atom is from the 4s orbital. Its set of quantum numbers, which describe its state, are (4,0,0,±1/2).

The electron lost to form the potassium (K) ion from the K atom would be the electron in the highest energy level, or the outermost shell, of the atom. This shell, also called the valence shell, contains only one electron for Potassium. This electron can be characterized by its four quantum numbers: the principal quantum number (n), the azimuthal quantum number (l), the magnetic quantum number (m), and the spin quantum number (ms).

For potassium, this electron resides in the 4s orbital. So the set of quantum numbers for this electron would be: n=4 (fourth energy level), l=0 (s orbital), m=0 (orientation of the orbital), and ms=±1/2 (two possible spin states). Thus, the set of quantum numbers for the electron lost to form the K ion from the K atom is (4,0,0,±1/2).

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To find the density of sulfur dioxide (SO2) at 1.2 atmospheres and 271 Kelvin, we can use the ideal gas law equation. We need to know the molar mass of sulfur dioxide, which is 64.06 g/mol. Using the ideal gas law equation, we can calculate the volume of SO2 and find the density.

To find the density of sulfur dioxide (SO2) at 1.2 atmospheres and 271 Kelvin, we can use the ideal gas law equation:

density = (mass of SO2) / (volume of SO2)

We need to know the molar mass of sulfur dioxide, which is 64.06 g/mol. We also need to convert the given pressure to Pascals (Pa) and temperature to Kelvin (K).

Using the ideal gas law equation, we can calculate the volume of SO2:

volume of SO2 = (mass of SO2) / (density)

Finally, we substitute the given values into the equation to find the density:

density = mass of SO2 / volume of SO2

The solubility product (Ksp) of barium chromate (BaCrO₄) is approximately 1.227 × 10⁻¹⁰.

Given information,

Solubility of barium chromate = 2.81 × 10⁻³ g/l

The molar solubility (S) is the number of moles of the compound that dissolve per liter of solution.

Molar mass of BaCrO₄ = (atomic mass of Ba) + (atomic mass of Cr) + 4 (atomic mass of O)

Molar mass of BaCrO₄ = 137.33 + 51.996 + 4 × 16.00

Molar mass of BaCrO₄= 137.33 + 51.996 + 64.00

Molar mass of BaCrO₄= 253.326 g/mol

Molar solubility (S) = (mass of BaCrO₄/ molar mass of BaCrO₄)

S = (2.81 × 10⁻³)/(253.326 )

S = 1.108 × 10⁻⁵ mol/L

Since the stoichiometric coefficients of BaCrO₄ are 1 for both barium ions (Ba²⁺) and chromate ions (CrO₄²⁻), the solubility product can be calculated as:

Ksp = [Ba²⁺][CrO₄²⁻]

Ksp ≈ 1.108 × 10⁻⁵  × 1.108 × 10⁻⁵

Ksp = 1.227 × 10⁻¹⁰

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Democritus, a Greek philosopher, proposed the idea of atomos or atomon - tiny, indivisible, solid objects - as the building blocks of all matter in the universe. His atomic theory challenged the prevailing belief of the time and laid the foundation for modern understanding of matter.

About 2,500 years ago, Democritus, a Greek philosopher, proposed the idea that all matter in the universe is made up of tiny, indivisible, solid units called atomos or atomon. He believed that these atoms were the building blocks of all substances and that they cannot be further divided. This theory challenged the prevailing belief of the time that the universe was a single, unchangeable entity. Democritus' atomic theory laid the foundation for modern understanding of matter and influenced later scientists such as John Dalton and Albert Einstein.

Answer : The heat released during the reaction is [tex]-8.4\times 10^3kJ[/tex]

Explanation :

First we have to calculate the number of moles of octane [tex](C_8H_{18})[/tex].

[tex]\text{Moles of }C_8H_{18}=\frac{\text{Mass of }C_8H_{18}}{\text{Molar mass of }C_8H_{18}}[/tex]

Molar mass of [tex]C_8H_{18}[/tex] = 114 g/mole

[tex]\text{Moles of }C_8H_{18}=\frac{75g}{114g/mole}=0.658mole[/tex]

Now we have to calculate the heat released during the reaction.

[tex]\Delta H=\frac{q}{n}[/tex]

or,

[tex]q=\Delta H\times n[/tex]

where,

[tex]\Delta H[/tex] = enthalpy change = -5500 kJ/mol

q = heat released = ?

n = number of moles of [tex]C_8H_{18}[/tex] = 0.658 mol

Now put all the given values in the above formula, we get:

[tex]q=(-5500kJ/mol)\times (0.658mol)=-8358.66kJ=-8.4\times 10^3kJ[/tex]

Therefore, the heat released during the reaction is [tex]-8.4\times 10^3kJ[/tex]

The quantity of heat released when the octane is burned completely is -3,613.5 Joules.

Given the following data:

To find the quantity of heat released when the octane is burned completely:

First of all, we would determine the number of moles of octane in this chemical reaction.

[tex]Number\;of\;moles \;(C_8H_{18})= \frac{Mass\; of\;octane}{Molar\;mass\;of\;octane}[/tex]

Substituting the values into the formula, we have;

[tex]Number\;of\;moles \;(C_8H_{18})= \frac{75}{114.23}[/tex]

Number of moles ([tex]C_8H_{18}[/tex]) = 0.657 moles.

Now, we can find the quantity of heat released when the octane is burned completely:

1 mole of octane = -5,500 kJ/mol

0.657 mole of octane = X kJ/mol

Cross-multiplying, we have:

[tex]X = -5500[/tex] × [tex]0.657[/tex]

X = -3,613.5 Joules.

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[tex]\boxed{{\text{0}}{\text{.15 mol}}}[/tex] of [tex]{\text{HN}}{{\text{O}}_{\text{3}}}[/tex] is present in the dilute solution.

Further Explanation:

The proportion of substance in the mixture is called concentration. The most commonly used concentration terms are as follows:

1. Molarity (M)

2. Molality (m)

3. Mole fraction (X)

4. Parts per million (ppm)

5. Mass percent ((w/w) %)

6. Volume percent ((v/v) %)

Molarity is a concentration term that is defined as the number of moles of solute dissolved in one litre of the solution. It is denoted by M and its unit is mol/L.

The formula to calculate the molarity of [tex]{\text{HN}}{{\text{O}}_{\text{3}}}[/tex] solution is as follows:

[tex]{\text{Molarity of HN}}{{\text{O}}_3}\;{\text{solution}} = \frac{{{\text{Moles}}\;{\text{of}}\;{\text{HN}}{{\text{O}}_3}}}{{{\text{Volume }}\left( {\text{L}} \right){\text{ of}}\;{\text{HN}}{{\text{O}}_3}\;{\text{solution}}}}[/tex]            …… (1)

Rearrange equation (1) to calculate the moles of [tex]{\text{HN}}{{\text{O}}_{\text{3}}}[/tex].

[tex]{\text{Moles}}\;{\text{of}}\;{\text{HN}}{{\text{O}}_3} = \left( {{\text{Molarity of HN}}{{\text{O}}_3}\;{\text{solution}}} \right)\left( {{\text{Volume of}}\;{\text{HN}}{{\text{O}}_3}\;{\text{solution}}} \right)[/tex]    …… (2)

The volume of [tex]{\text{HN}}{{\text{O}}_{\text{3}}}[/tex] solution is to be converted into L. The conversion factor for this is,

[tex]{\text{1 mL}} = {10^{ - 3}}\;{\text{L}}[/tex]  

So the volume of [tex]{\text{HN}}{{\text{O}}_{\text{3}}}[/tex] solution is calculated as follows:

[tex]\begin{aligned}{\text{Volume of HN}}{{\text{O}}_{\text{3}}}\;{\text{solution}}&=\left( {{\text{25 mL}}}\right)\left({\frac{{{{10}^{ - 3}}\;{\text{L}}}}{{{\text{1 mL}}}}} \right)\\&=0.02{\text{5 L}}\\\end{aligned}[/tex]

The molarity of [tex]{\text{HN}}{{\text{O}}_{\text{3}}}[/tex] solution is 6M.

The volume of [tex]{\text{HN}}{{\text{O}}_{\text{3}}}[/tex] solution is 0.025 L.

Substitute these values in equation (2).

[tex]\begin{aligned}{\text{Moles}}\;{\text{of}}\;{\text{HN}}{{\text{O}}_3}&=\left( {{\text{6 M}}} \right)\left( {0.02{\text{5 L}}} \right)\\&=0.1{\text{5 mol}} \\ \end{aligned}[/tex]

The number of moles of [tex]{\text{HN}}{{\text{O}}_{\text{3}}}[/tex] in 25 mL solution is 0.15 mol.

Dilution is the conversion of a concentrated solution into a dilute solution with the addition of extra solvent but the amount of solute is unaltered. The change that arises is an increase in the volume of the solution.

In the given solution, dilution is done and the concentration of solution decreases during the process. But the number of moles of solute remains unaltered. Therefore the number of [tex]{\text{HN}}{{\text{O}}_{\text{3}}}[/tex] in the dilute solution is also 0.15 mol.

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Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Concentration terms

Keywords: molarity, HNO3, dilution, moles of HNO3, volume, solution, 0.15 mol, concentration, 25 mL, 6 M, concentrated solution, dilute solution.

After adding 46.0 mL of 0.50 M KOH to 92.0 mL of 0.25 M HBr, the solution is neutral and has a pH of approximately 7.

To determine the pH of the solution when 46.0 mL of 0.50 M KOH is added to 92.0 mL of 0.25 M HBr at 25°C, follow these steps:

Calculate the moles of HBr and KOH:

Moles of HBr: 0.25 M × 0.092 L = 0.023 moles

Moles of KOH: 0.50 M × 0.046 L = 0.023 moles

Determine the reaction completeness:

KOH completely neutralizes an equivalent amount of HBr (1:1 ratio):

0.023 moles of HBr neutralized by 0.023 moles of KOH.

Calculate the pH:

After the neutralization, there are no excess moles of acid (H+) or base (OH-), resulting in neutral pH.

The pH of the resulting solution is therefore approximately 7.

In summary, after adding 46.0 mL of 0.50 M KOH to 92.0 mL of 0.25 M HBr, the solution is neutral, with a pH of approximately 7

Final answer:

The fastest reaction will be option d: a 2.0 gram sample of powdered zinc in 0.50 M hydrochloric acid, due to the greater surface area of the powdered zinc and the higher concentration of the acid.

Explanation:

When zinc metal is submerged into aqueous hydrochloric acid, a chemical reaction occurs that produces zinc chloride and hydrogen gas. The balanced equation for this reaction is:

Zn(s) + 2HCl(aq) → H₂(g) + ZnCl₂(aq)

This reaction is faster when the surface area of the zinc is increased and the concentration of hydrochloric acid is higher. Thus, option d, a 2.0 gram sample of powdered zinc in 0.50 M hydrochloric acid, will react the fastest because the powdered form of zinc has a larger surface area than a lump, allowing more acid to react with it at the same time. Additionally, a higher concentration of hydrochloric acid, such as 0.50 M compared to 0.10 M, will provide more acid particles in the solution to react with the zinc, thus speeding up the reaction.

To determine the number of atoms in 1.85 ml of mercury, convert the volume to mass using the density of mercury. Then, calculate the number of moles of mercury using its atomic mass. Finally, use Avogadro's number to calculate the number of atoms in the given amount of mercury.

To determine the number of atoms in 1.85 ml of mercury, we need to convert the volume to mass using the density of mercury. The density of mercury is 13.5 g/ml. So, the mass of 1.85 ml of mercury is 1.85 ml x 13.5 g/ml = 24.975 g.

Next, we need to calculate the number of moles of mercury using its atomic mass. The atomic mass of mercury is 200.59 g/mol. To find the number of moles, we divide the mass (in grams) by the molar mass: 24.975 g / 200.59 g/mol = 0.1245 mol.

Finally, we can calculate the number of atoms in 0.1245 mol of mercury. Avogadro's number tells us that there are 6.022 x 10^23 atoms in 1 mol of any substance. So, the number of atoms in 0.1245 mol of mercury is 0.1245 mol x 6.022 x 10^23 atoms/mol = 7.49 x 10^22 atoms.

The equilibrium constant indicates the ratio of product and reactant concentrations at equilibrium. The processes in the first equation involve the formation and decomposition of gases. The K value for the second equation is calculated using given equilibrium concentrations.

The equilibrium constant (K) for a chemical reaction indicates the ratio of the concentrations of the products to the concentrations of the reactants at equilibrium. In the first equation, 2CO(g) + O2(g) → 2CO2(g), the forward reaction is the formation of CO2 from CO(g) and O2(g), while the reverse reaction is the decomposition of CO2(g) into CO(g) and O2(g).

To find the value of K for the reaction 2HI(g) → H2(g) + I2(g), we need to use the given equilibrium concentrations. Using the equation K = [H2][I2]/[HI]^2, we plug in the values to get K = (0.010)(0.010)/(0.80)^2 = 0.00015625.

Final answer:

The reaction represented by the equation 2CO(g) + O2(g) ↔ 2CO2(g) involves the formation and decomposition of carbon dioxide. The equilibrium constant (K) for the reaction 2HI(g) ↔ H2(g) + I2(g) at 520°C is 0.00015625.

Explanation:

The reaction represented by the equation 2CO(g) + O2(g) ↔ 2CO2(g) is an equilibrium reaction. It involves two processes: the formation of carbon dioxide from carbon monoxide and oxygen, and the reverse process where carbon dioxide decomposes to form carbon monoxide and oxygen.

At a temperature of 520°C, we are given the equilibrium concentrations of HI (0.80 M), H2 (0.010 M), and I2 (0.010 M). To find the equilibrium constant (K) for the reaction, we can use the formula:

K = [H2][I2]/[tex][HI]^2[/tex]

Substituting the given concentrations into the formula:

K = (0.010)(0.010)/[tex](0.80)^2[/tex] = 0.00015625

Answer: water freezing.

Explanation:

Answer:

The right answer is C.

Oxidation is the loss of electrons. A loss of electrons will appear as an increase in the positive charge of the element as it is converted to an ion. Here we have aluminum have an oxidation state equals zero as a reactant because it is in the element state. After reacting, it combines with three atoms chlorine where each chlorine atom usually has an oxidation state equals -1, therefore, we have -3 charges which have to be neutralized with the 3+ charges of aluminum.

The statement which correctly describe a half-reaction is option C, i.e., Al is oxidized from 0 to +3. At elemental stage as Al, it possess no charge but, when combined with an electronegative atom aluminum gets positively charged.

A redox reaction is the combination of oxidation and reduction reaction. Oxidation is the losing electrons and gets into higher oxidation state whereas, reduction is just the opposite where, one species reduces to its lower oxidation state.

All species in their elemental state carries no charge and thus assume an oxidation state of 0. Thus  Al and H₂ have no charge. Hydrogen is in +1 oxidation state in HCl and Al is in +3 oxidation state in AlCl₃ since, Cl has a negative charge hence, 3 Cl possess 3 unit of negative charge.

In the overall reaction, Al is thus oxidised from 0 to +3 oxidation state, whereas, H is reduced from +1 to 0. Hence, option A is correct.

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Answer:

I think it’s CU

Explanation:

Different 3d states that does the hydrogen atom have are 10.

The energy state is also familiarly known as the energy level plays a vital role in explaining the atomic structure. The energy levels or the energy state is any discrete (definite) value from a set of values of total energy for a subatomic particle confined by a force to limited space or for a system of such particles, for example like an atom or a nucleus.

The energy level is an old name used with the electron orbits of the Bohr model before quantum mechanics. In the quantum mechanical treatment and because of the uncertainty principle, thus we can not have orbits and hence the term energy states are used instead, thus technically there is not much of a difference between energy levels and energy states.

An electron in a hydrogen atom would have 10 states for a 3d orbital, like any other element.

n = 3, l = 2, in one of ml = 2, 1, 0, -1, -2 each with ms = -½ or +½ or a total of 10 possible states.

None of these are a ground state of an electron in the hydrogen atom.

Therefore, Different 3d states that does the hydrogen atom have are 10.

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