Can someone help mee, pls show the works.. Thx

Sugar is a pure substance, specifically, it is classified as a compound composed of carbon, hydrogen, and oxygen atoms. As such, the answer to the multiple-choice question is (a) pure substance compound.

Sugar is a type of substance that is considered to be a pure substance compound. A compound is a chemical substance composed of many identical molecules composed of atoms from more than one element. In the case of sugar, specifically sucrose, it is composed of carbon, hydrogen, and oxygen atoms.

A pure substance is a material that has a constant composition and cannot be separated into its constituent parts without undergoing a chemical reaction. Sugar meets this definition as it is composed of the same type of molecule throughout the entire substance.

Therefore, the answer is (a) pure substance-compound.

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Liquid freezing is an  endothermic reaction  and all other statements are exothermic,exothermic,endothermic,exothermic reactions respectively.

An endothermic reaction is defined as a chemical reaction which is a thermodynamic process accompanied by an increase in enthalpy of the system.In this process, a system absorbs energy from the surroundings which is mainly thermal energy.

Thus an endothermic reaction leads to an increase in the temperature of the system with a decrease in the temperature of the surroundings.Endothermic reactions usually involve the formation of bonds which requires input of energy.In endothermic reactions, entropy of the surrounding decreases.

Many endothermic processes involve the physical changes rather the chemical changes.In an endothermic reaction ,the potential energy of products is greater than that of reactants.

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Final answer:

An exothermic process releases heat, while an endothermic process absorbs heat. Liquid freezing, gas cooling and condensing, and a warm beaker after mixing chemicals are exothermic. Solid melting and liquid turning into gas are endothermic.

Explanation:

We can label each process as either endothermic or exothermic based on whether the process absorbs or releases heat, respectively. Here is the labeling for each of the given processes:

The transition of substances between different phases and the chemical reactions that release or absorb heat are classified as either exothermic or endothermic.

3 is the number of water molecules associated with each [tex]Al_2(SO_4)_3[/tex] unit.

Molecules are made up of one or more atoms.

The molecular mass of Al₂(SO₄)₃·xH₂O

(27×2)+(32×3)+(16×12)+(x×18)

= 342 + 18x g

Molecular mass of Al₂:

27×2 = 54 g

54g contains 13.63% Al by mass.

(342+18x)g contains 100%

So,

0.1363 (342+18x) = 54

46.6146 + 2.4534x = 54

2.4534x = 7.3854

x ≈ 3

Hence, 3 is the number of water molecules associated with each [tex]Al_2(SO_4)_3[/tex] unit.

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The right answer is:

*Hydrogen bonding occurs when a hydrogen atom is covalently bonded to an N, O, or F atom.

*A hydrogen bond is possible with only certain hydrogen-containing compounds.

*A hydrogen atom acquires a partial positive charge when it is covalently bonded to an F atom.

Watch the animation and identify the correct conditions for forming a hydrogen bond. check all that apply..

This animation showing the transient hydrogen bonding between water molecules.Each water molecule (H2O) has two hydrogens and two lone pairs of electrons on the oxygen, therefore it can make up to four hydrogen bonds with neighbouring molecules.

Grade:  9

Subject:  Chemistry

Chapter:  hydrogen bond

Keywords: hydrogen bond, covalent bond, hydrogen-containing compounds, partial positive charge, compounds

Hydrogen bonding occurs when a hydrogen atom is covalently bonded to an n, o, or f atom.

A hydrogen bond is possible with only certain hydrogen-containing compounds.

A hydrogen atom acquires a partial positive charge when it is covalently bonded to an f atom.

Hydrogen bonding occurs when a hydrogen atom is covalently bonded to an nitrogen, oxygen, or fluorine atom in which hydrogen shares its electron with these atoms and as a result both atoms get stability. In this type bonding, no complete transfer of electron occurs.

But the electron moves to the atom that have the highest electronegativity value which results in bearing of partial positive charge on hydrogen and partial negative charge on the atom which attracts that electron so we can conclude that hydrogen atom acquires a partial positive charge when it is covalently bonded to nitrogen, oxygen, or fluorine atom atom.

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Answer:

Average in size 100% Im not sure about mass, I think it's small correct me if not.

Explanation:

just had this

The d sublevel holds two more atomic orbitals than the p sublevel, with the p subshell having three orbitals and the d subshell having five orbitals.

The question is about the number of atomic orbitals in different sublevels of an atom, specifically comparing d and p sublevels. In any atom, the sublevels, denoted by s, p, d, and f, have a specific number of orbitals where an electron can most probably be. The p subshell contains three orbitals, while the d subshell contains five orbitals. Therefore, the d sublevel holds two more atomic orbitals than the p sublevel.

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Kepler discovered the laws of planetary motion, including orbits being ellipses, equal areas swept out in equal times, and the period of revolution being related to the semi-major axis.

Kepler discovered that:

Each planet moves around the Sun in an orbit that is an ellipse, with the Sun at one focus.

The radius vector from Sun to planet sweeps out equal areas in equal times.

The planet's period of revolution squared is proportional to the cube of the semi-major axis of the ellipse.

There are 1.08 grams of co2 contained in 550 ml of the gas at stp

Given that    Volume of gas   =550 ml   = 0. 550  L

                 Standard Temperature  =  T  = 273.15 K

                 Standard Pressure  =  P  =  1 atm

                 Gas Constant  =  R  =  0.08205 L⋅atm⋅K⁻¹⋅mol⁻¹

        Mass=?

From the question,    the CO₂ gas is acting ideally so we will apply Ideal Gas equation;

                              P V  =  n R T

Solving for n,

                             n  =  P V / R T

Putting values,

               n  =  1 atm × 0.55 L / 0.08205 L⋅atm⋅K⁻¹⋅mol⁻¹ × 273.15 K

               n  =  0.0245 moles

Remember that  

Number of Moles  =  Mass / Molar.Mass

Solving for Mass,

Mass  =  Moles × M.Mass

Mass  =0.0245 mol × 44.01 g/mol

Mass = 1.08 grams of CO₂

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Answer : Option A) [tex] NH_{4}^{+} and NH_{3} [/tex]

Explanation : [tex] NH_{4}^{+} and NH_{3} [/tex] are considered as an acid-conjugate base pair, because[tex] NH_{4}^{+}[/tex] is an acid with a proton extra in its compound which makes it more acidic and rich in proton, while [tex] NH_{3} [/tex] is found to be the conjugate base of [tex] NH_{4}^{+} [/tex] as it does not contains the [tex]H^{+}[/tex] ions.

[tex] NH_{4}^{+} and H_{3}O^{+} [/tex] both are acids, and the last option where both [tex] H_{2}O and NH_{3} [/tex] can be considered as bases.

The reaction which is an acid-conjugate base pair is NH4+. This is the conjugate acid of NH3

An acid-conjugate base pair is a pair of substances that would have been similar in chemical composition but for the presence of one proton (H+).

To form a conjugate Acid, one proton must be added to a base. To create a conjugate Base on the other hand, one proton must be removed from an acid.

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To find the final volume of a gas when the temperature increases at constant pressure, apply Charles's Law. The final volume of the 500 ml gas sample that is heated from 150 K to 350 K is calculated to be 1166.67 ml.

The problem relates to Charles's Law, which states that for a fixed amount of gas at constant pressure, the volume is directly proportional to its temperature in Kelvin. If we know the initial volume and temperature of a gas sample and the temperature changes, we can use Charles's Law (V1/T1 = V2/T2) to find the final volume of the gas.

To calculate the final volume of the 500 ml sample of gas that increases in temperature from 150 K to 350 K while keeping the pressure constant, we use the formula:

V1/T1 = V2/T2

Substituting in the given values:

500 ml / 150 K = V2 / 350 K

We solve for V2:

V2 = 500 ml × (350 K / 150 K)

V2 = 500 ml × (7/3)

V2 = 1166.67 ml

The final volume of the gas will be 1166.67 ml.

Answer: The molecular formula for this compound is [tex]Na_3PO_4[/tex]

Explanation:

We are given a chemical compound known as sodium phosphate. It is formed by the interaction of oppositely charged ions.

The ions forming this compound are sodium ion [tex](Na^+)[/tex] and phosphate ion [tex](PO_4^{3-})[/tex]

To know the chemical formula for a compound, we use criss-cross method, in which the charge of the ion becomes the subscript of the other ion.

Hence, the molecular formula for given compound will be [tex]Na_3PO_4[/tex]

Answer:

O2- is an anion

Explanation:

An atom or molecule is said to be neutral when it has a zero net charge. In contrast, if the system has a net charge it is termed as an ion.

A cation is an atom or a molecular system with a net positive charge whereas an anion carries a net negative charge.

In the given examples:

Ca2+ : net positive, cation

Ag+: net positive, cation

O2-: net negative, anion

K+: net positive, cation

Final answer:

The statement is true; substitute natural gas can be synthesized by passing carbon monoxide and hydrogen over a nickel or cobalt catalyst at 400°C, as part of the process of producing syngas, which can be further converted into other hydrocarbons.

Explanation:

The statement that substitute natural gas can be synthesized by passing carbon monoxide (CO) and hydrogen (H₂) over Ni (nickel) or Co (cobalt) at 400°C is true. This process is part of producing syngas (synthesis gas), which primarily consists of CO and H₂. When these gases are passed over a Ni or Co catalyst at the temperature mentioned, it can lead to the production of a mixture suitable for further conversion into substitute natural gas or other hydrocarbons.

The efficiency of this process and the resulting H₂/CO ratio is influenced by the catalytic material and operation conditions. It is important to note that syngas, obtained by reacting methane with steam over a Ni catalyst at high temperatures (700 - 1100 °C), can then be used as a precursor to produce a wide range of fuels when combined in the correct ratios over a suitable catalyst.

The change in reaction rate when doubling the concentration of [b] is dependent on the rate law of the reaction. For one-to-one stoichiometry, the reaction rate should double. However, reaction orders for more complex reactions may alter the rate differently.

In changing the concentration of reactant [b] in any reaction, the change in reaction rate is dependent on what is known as the 'rate law,' and cannot be predicted without knowledge of this law. In simple reactions, typically found in elementary chemistry, if the reaction has a one-to-one stoichiometry, like aA → bB, doubling the concentration of a reactant, in this case [b], will double the rate of reaction. This means, if changes in concentration of [b] only affect the reaction rate, then doubling [b] should double the reaction rate. However, for more complex reactions, we use the concept of reaction orders. The exponent on the concentration term in the rate law, sometimes referred to as 'n' in this context, dictates how a change in [b] alters the reaction rate. If n=1, doubling [b] would indeed double the reaction rate, but if n=2, doubling [b] would quadruple the rate, and so forth.

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The reaction rate of the provided rate law changes by a factor of the square root of two, or approximately 1.41, when the concentration of reactant B is doubled, all else remaining constant.

It refers to the change in reaction rate given a rate equation when the concentration of one reactant (B) is doubled, with the other reactant concentrations held constant. According to the provided rate law,

Rate=k [B][tex]^{\frac{1}{2}}[/tex] [C]²,

when the concentration of B is doubled, the reaction rate changes by the square root of two. Since the order of reaction concerning B is 1/2, the effect of doubling the concentration of B can be represented mathematically as:

New rate when [B] is doubled:

[tex]k(2[B])^{\frac{1}{2}} [C]^{2}[/tex] = 2[tex]^{ \frac{1}{2} }[/tex]R

The factor changes in rate = 1.41R

Therefore, the reaction rate changes by a factor of [tex]\sqrt{2}[/tex] or approximately 1.41, when the concentration of B is doubled.

The enthalpy change for the combustion of ethanol can be calculated using the enthalpies of formation and applying Hess's law. It's determined by the difference in the products and reactants enthalpy of formation. The enthalpy change for the combustion of ethanol is -1366 kJ per mole of ethanol burned.

To determine the enthalpy change for the combustion of ethanol C₂H5OH(l) + 3 O2(g) → 2 CO2(g) + 3 H2O(g), we need to apply the concept known as Hess's law. In simple terms, Hess's law states that the total enthalpy change of a chemical reaction is the sum of the enthalpy changes for the steps of the process.

Here, we know the enthalpies of formation for the reactants and products involved. Enthalpies of formation are defined for one mole of a substance formed from its elements in their standard states. The enthalpies of formation for the substances involved are ethanol (C₂H5OH(l)) -278 kJ/mol, water (H₂O(l)) -286 kJ/mol, and carbon dioxide (CO2(g)) -394 kJ/mol.

The enthalpy change of the reaction ΔH = Σ[ (products moles x products enthalpy of formation) - (reactants moles x reactants enthalpy of formation) ]

On substituting the numbers we get ΔH = [ (2 mol CO₂ x -394 kJ/mol CO₂) + (3 mol H2O x -286 kJ/mol H2O) ] - [ (1 mol C2H5OH x -278 kJ/mol C2H5OH) + (3 mol O2 x 0 kJ/mol O2) ].

So, ΔH = [ -788 kJ + -858 kJ ] - (-278 kJ) = -1366 kJ

Thus, the enthalpy change for the combustion of ethanol is -1366 kJ per mole of ethanol burned.

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Answer: The correct answer is metals.

Explanation:

Ions are formed when an atom gains or looses electrons.

When an atom looses electrons, it tends to form positive ions known as cations.

When an atom gains electrons, it tends to form negative ions known as anions.

Metals are the elements which looses electrons to form positive ions. For Example: Sodium will loose 1 electron to form [tex]Na^+[/tex] ions.

Non-metals are the elements which gains electrons to form negative ions. For Example: Chlorine will gain 1 electron to form [tex]Cl^-[/tex] ion.

Hence, the correct answer is metals.

Answer : The number of moles of oxygen atoms are 135 moles.

Explanation : Given,

Moles of [tex]Fe(NO_3)_3[/tex] = 15.0 mole

The given chemical formula is, [tex]Fe(NO_3)_3[/tex]

By the mole concept:

In [tex]Fe(NO_3)_3[/tex], there are 1 mole of iron (Fe) atom, 3 moles of nitrogen (N) atoms and 9 moles of oxygen (O) atoms.

As, 1 mole of [tex]Fe(NO_3)_3[/tex] contains 9 moles of oxygen atoms

So, 15.0 moles of [tex]Fe(NO_3)_3[/tex] contains [tex]15.0\times 9=135[/tex] moles of oxygen atoms.

Hence, the number of moles of oxygen atoms are 135 moles.

Answer:

c. destruction of the ozone layer

Explanation:

The destruction of the Ozonoe Layer is causing for example that the world starts to heat, and global warming is a direct consequence of the destruction of the ozone layer, but the acid precipitation is cause by certain gases that are emitted by human activity like industries, that get trapped in the drops of rain fall and make acidic rain.

Answer:

The percent of oxalic acid in a solid is 48.87%.

Explanation:

Mass of the solid sample = 0.7984 g

[tex]H_2C_4O_4+2NaOH\rightarrow Na_2C_2O_4+2H_2O[/tex]

Volume of NaOH solution = 37.98 mL = 0.03798 L

Concentration or molarity of the NaOH solution = 0.2283 M

Moles of NaOH :

[tex]Molarity\times \text{Volume of the solution} = 0.0086708 moles[/tex]

According to reaction,  2 moles of sodium hydroxide reacts with 1 mole of oxalic acid .

Then 0.0086708 moles of sodium hydroxide will react with:

[tex]\frac{1}{2}\times 0.0086708 moles=0.0043354 moles[/tex] of oxalic acid.

Mass of oxalic acid neutralized = 0.0043354 moles × 90 g/mol =0.390186 g

Percentage of oxalic acid in solid sample :

[tex]\%=\frac{\text{Mass of oxalic acid}}{\text{Mass of sample}}\times 100[/tex]

[tex]\%=\frac{0.390186 g}{0.7984 g}\times 100=48.87 \%[/tex]

The percent of oxalic acid in a solid is 48.87%.

A precipitate is an insoluble product formed, when two solutions are mixed, this reaction is called precipitation reaction.

The balanced equation for this reaction is:

2 AgNO3 + K2CrO4 (aq)------->Ag2CrO4 (s) + 2 KNO3

so when silver nitrate and potassium chromate solutions are mixed, precipitates of silver nitrate are formed.

Explanation:

When we obtain insoluble solid from a liquid solution, then this insoluble solid is known as precipitate.

When silver nitrate and potassium chromate solutions are mixed together then there is formation of silver chromate and potassium nitrate.

The reaction is as follows.

     [tex]2AgNO_{3}(aq) + K_{2}CrO_{4}(aq) \rightarrow Ag_{2}CrO_{4}(s) + 2KNO_{3}(aq)[/tex]

This insoluble solid [tex]Ag_{2}CrO_{4}[/tex] is the precipitate and it has a red-brown color.