Which of the following represents a purely covalent bond?

Ne – Ne

Na – Na

N – N

Ni – O

Answer: Option (a) is the correct answer.

Explanation:

A substance that does not get consumed in a chemical reaction and helps in increasing rate of the reaction by lowering the activation energy is known as a catalyst.

Hence, when the chemist finds that reaction speeds up when platinum is added into the reaction then the chemist must calculate or measure the mass of platinum before and after the completion of reaction.

This is because if there occurs change in the mass of platinum then it means that platinum is not acting as a catalyst in the reaction.

Thus, we can conclude that chemist must measure the mass of the platinum to determine whether it is a catalyst.

Answer:

7.56 moles

Explanation:

For a 742 kPa, we can consider the gas as an ideal gas because it will be close to 7 atm (1 kPa = 0.01 atm), which is low pressure. So, the ideal gas equation is:

PV = nRT

Where P is the pressure, V is the volume, n the number of moles, R the gas constant and T the temperature (always in Kelvin). For pressure in kPa and volume in liters, R = 8.314 kPa.L/mol.K, then:

742x25 = nx8.314x295

2452.63n = 18550

n = 18550/2452.63

n = 7.56 moles

Answer: The correct answer would 100% be A.  Experiments showed that the atom is made of smaller particles.

just took the test and got it right

Final answer:

Propane's complete combustion reaction with oxygen producing carbon dioxide and water is a chemical process, representing a typical exothermic combustion reaction used for heat generation.

Explanation:

The combustion of propane (C3H8) in the presence of oxygen (O2) to produce carbon dioxide (CO2) and water vapor (H2O) is a chemical reaction that involves the breaking and forming of chemical bonds.

The balanced chemical equation for this reaction is:

The balanced chemical equation for the complete combustion of propane is C3H8 + 5O2 → 3CO2 + 4H2O. This reaction is exothermic, releasing heat energy which is why propane is commonly used as a fuel source.

"the addition of negatively charged electrons" is the answer.

Explanation:

Systems which occur in the nature on their own are known as natural system. On the other hand, systems which are made by human beings are known as human-made systems.

Therefore, classifying given systems as follows.

Natural systems are:

Human-made system are:

B. This looks like ice turning to water then to steam

Answer is: B.) A solid gains kinetic energy to become a liquid and then becomes a gas.

Stage 2 is melting (from solid to liquid) and Stage 2 is boiling (from liquid to gas).

In solid, molecules are closely packed, stiff and do not changes of shape or volume. Solid object does not take on the shape of its container.

Liquids have definite volume, but no fixed shape.

Gases not have definite volume and fixed shape, it depends on its container.

Answer:

Exothermic

Explanation:

From the perspective of thermodynamics, chemical reactions can be broadly

classified as endothermic and exothermic reactions.

Endothermic reactions are accompanied by the absorption of heat and have a negative value for the reaction enthalpy i.e. ΔH is negative. In contrast, exothermic reactions are accompanied by the release of heat and have a positive value for the reaction enthalpy i.e. ΔH is positive.

The given reaction is:

[tex]N2(g) + 3H2(g)---- 2NH3(g) + 100.4 kJ[/tex]

Based on the above reaction, production of NH3 is accompanied by the release of 100.4 kJ of heat, hence this is an exothermic reaction.

This is a true statement.

Answer:

Zn + Ag+ → Zn2+ + Ag

Explanation:

Plato

The statement of the redox reactions is spontaneous as "[tex]Zn + Ag^{+}[/tex]→ [tex]Zn^{2+} + Ag[/tex] ".

A redox reaction is the process in which electrons are exchanged between two reactants that are involved. The oxidation number of a molecule, atom, or ion varies as a result of gaining or losing an electron.

If the standard electrode potential for the redox reaction, [tex]E^{0}[/tex], is positive, the redox reaction is spontaneous. That means, the reaction will move forward if [tex]E^{0}[/tex] is positive. In this reaction, silver ion is the oxidizing agent that readily accepts the electron to attain (stable configuration) the metal state, while Zn is a reducing agent which loses electrons (i.e., oxidized) by causing a reduction. It proceeds with[tex]E^{0}[/tex] redox reaction as given, the reaction moves forward and is considered to be spontaneous.

Hence the correct answer is [tex]Zn + Ag^{+}[/tex] → [tex]Zn^{2+} + Ag[/tex].

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[tex]\boxed{{\text{7}}{\text{.182 g}}}[/tex] of [tex]{\text{CuS}}{{\text{O}}_{\text{4}}}[/tex] would be needed to make 150 mL of 0.300 M [tex]{\text{CuS}}{{\text{O}}_4}[/tex] 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{CuS}}{{\text{O}}_4}[/tex] solution is as follows:

[tex]{\text{Molarity of CuS}}{{\text{O}}_4}\;{\text{solution}}=\dfrac{{{\text{Moles}}\;{\text{of}}\;{\text{CuS}}{{\text{O}}_4}}}{{{\text{Volume }}\left( {\text{L}}\right){\text{ of}}\;{\text{CuS}}{{\text{O}}_4}\;{\text{solution}}}}[/tex]   ......(1)

Rearrange equation (1) to calculate the moles of [tex]{\text{CuS}}{{\text{O}}_4}[/tex].

[tex]{\text{Moles}}\;{\text{of}}\;{\text{CuS}}{{\text{O}}_4}= \left( {{\text{Molarity of HN}}{{\text{O}}_3}\;{\text{solution}}} \right)\left( {{\text{Volume of}}\;{\text{CuS}}{{\text{O}}_4}\;{\text{solution}}} \right)[/tex]   ......(2)

The volume of [tex]{\text{CuS}}{{\text{O}}_4}[/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{CuS}}{{\text{O}}_4}[/tex] solution is calculated as follows:

[tex]\begin{aligned}{\text{Volume of CuS}}{{\text{O}}_4}\;{\text{solution}}&= \left( {{\text{150 mL}}}\right)\left({\frac{{{{10}^{ - 3}}\;{\text{L}}}}{{{\text{1 mL}}}}} \right)\\&= 0.15{\text{ L}}\\\end{aligned}[/tex]

The molarity of [tex]{\text{CuS}}{{\text{O}}_4}[/tex] solution is 0.300 M.

The volume of [tex]{\text{CuS}}{{\text{O}}_4}[/tex] solution is 0.15 L.

Substitute these values in equation (2).

[tex]\begin{aligned}{\text{Moles}}\;{\text{of}}\;{\text{CuS}}{{\text{O}}_4}&=\left( {{\text{0}}{\text{.300 M}}} \right)\left( {0.15{\text{ L}}}\right)\\&= 0.04{\text{5 mol}}\\\end{aligned}[/tex]

The formula to calculate the mass of [tex]{\text{CuS}}{{\text{O}}_4}[/tex] is as follows:

[tex]{\text{Mass of CuS}}{{\text{O}}_{\text{4}}}=\left( {{\text{Moles of CuS}}{{\text{O}}_{\text{4}}}} \right)\left( {{\text{Molar mass of CuS}}{{\text{O}}_{\text{4}}}} \right)[/tex]       ......(3)

Substitute 0.045 mol for the moles of [tex]{\text{CuS}}{{\text{O}}_4}[/tex] and 159.609 g/mol for the molar mass of [tex]{\text{CuS}}{{\text{O}}_4}[/tex] in equation (3).

[tex]\begin{aligned}{\text{Mass of CuS}}{{\text{O}}_{\text{4}}}&= \left({{\text{0}}{\text{.045 mol}}} \right)\left( {\frac{{{\text{159}}{\text{.609 g}}}}{{{\text{1 mol}}}}}\right)\\&= 7.1824{\text{05 g}}\\&\approx {\text{7}}{\text{.182 g}}\\\end{aligned}[/tex]

Therefore the mass of [tex]{\mathbf{CuS}}{{\mathbf{O}}_{\mathbf{4}}}[/tex]  is 7.182 g.

Learn more:

1. Calculation of volume of gas: https://brainly.com/question/3636135

2. Determine the moles of water produced: https://brainly.com/question/1405182

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Concentration terms

Keywords: molarity, CuSO4, dilution, moles of CuSO4, volume, solution, 0.045 mol, 150 mL, 0.300 M, 7.182 g, 159.609 g/mol, 0.15 L.

The number of molecules in  12.5 g water is equal to 4.18 × 10²³ molecules.

Avogadro’s constant can be defined as the proportionality constant that uses to count the number of constituents such as ions, molecules, and atoms in the amount of substance in a sample.

Avogadro's constant can be defined as the approximate number of nucleons per gram of substance. The value of the Avogadro number is the mass of 1 mole of a compound, in grams, and is equal to the number of nucleons in 1 constituent particle.

The value of Avogadro’s constant is experimentally found to be approximately equal to 6.022×10²³ per mole.

The mass of the water = 12.5 g

The molar mass of the water = 18 g

The number of moles of the water = 12.5/18 = 0.694 mol

The number of molecules of water in one mole = 6.022 × 10²³

Number of molecules of water in 0.694 mol = 6.022 × 10²³× 0.694

= 4.18 × 10²³ molecules

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Answer:

B. The ionization energy increases because the ratio of the protons to electrons increases.

Explanation:

edg 2021

Core science provides a basic understanding of key scientific concepts, while double science goes further in depth and grants two GCSE qualifications upon completion. The choice between the two often depends on a student's academic and career aspirations in the field of science.

The main difference between core science and double science as part of the England GCSE OCR exam board involves the extent of the curriculum covered and the number of GCSE qualifications granted upon completion.

Core Science is a single award course which delivers one GCSE qualification. This course provides a broad and basic understanding of key scientific concepts, covering aspects of Biology, Chemistry, and Physics.

On the other hand, Double Science, also known as Combined Science, awards two GCSE qualifications. It covers a more extensive curriculum, diving deeper into the subjects of Biology, Chemistry, and Physics. This might be the preferred choice for students wishing to pursue sciences at A-level or beyond, as it provides a more comprehensive foundation in these subject areas.

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The new volume of the gas can be calculated using Boyle's law of gases. The volume of the gas when pressure drops from 90 kpa to 20 kpa, increases from 4 L to 18 L.

Boyle's law states that, at constant temperature, the volume of a gas is inversely proportional to the pressure of the gas.

hence, PV = a constant.

Let P1 and V1 be the initial pressure and volume and P2 and V2 be the final pressure and volume, then

P1 V1 = P2V2.

Given that,

P1 = 90 kPa

P2 = 20 kPa

V1 = 4 L

V2 = P1 V1/P2

     = (90kPa  × 4 L)/20 kPa

     = 18 L.

Therefore, the final volume of the gas will be 18 L.

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