A combination reaction occurs when one reactant forms two or more products true or false

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.

Answer:Primary

Explanation:

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.

Final answer:

In the decay of iodine-131 to xenon-131, a beta particle and gamma rays are emitted as the nucleus transitions from an unstable to a stable state.

Explanation:

When the radioactive nucleus of iodine-131 (131I_53) decays, it emits a beta particle (an electron, β) and transforms into an unstable form of xenon-131 (131Xe_54m), which is then followed by a gamma decay. The gamma decay involves the emission of gamma rays as the nucleus transitions from its excited state (131Xe_54m) to its ground state, resulting in a stable isotope of xenon-131 (131Xe_54). This process can be written as follows:

This type of decay is common in nuclear reactions and is one method of radioactive decay wherein unstable nuclei transition to a more stable form.

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 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.

The wave-mechanical model of the atom was proposed by Erwin Schrodinger that combined the works of Bohr and de Broglie. The electron was a three dimensional wave circling the nucleus in a whole number of wavelengths allowing the waveform to repeat itself as a stable standing wave (it can absorb energy form a nearby source which is oscillating at a proper frequency) representing the energy levels of Bohr model. He also said that Broglie’s model was correct about the matter waves and the electrons are located in the atomic space according to standing wave frequencies.

It's the 3rd option sis

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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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

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.

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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Answer:

0.23 = 23% O by mass

Explanation:

Hi! Let's solve this!

We have the percentage data of each component in the air and its masses.

Nitrogen 0.78084 28.013

Oxygen 0.20948 31.998

Argon 0.00934 39.948

Carbon dioxide 0.000375 44.0099

Neon 0.00001818 20.183

Helium 0.00000524 4.003

Methane 0.000002 16.043

Krypton 0.00000114 83.80

Hydrogen 0.0000005 2.0159

Nitrous oxide 0.0000005 44.0128

Now we have to calculate a molar fraction.

(0.20948 * 31.998) = (0.78084 * 28.013)

+ (0.20948 * 31.998) + (0.00934 * 39.948) + (0.000375 * 44.0099) + (0.00001818 * 20.183) + (0.00000524 * 4.003) + (0.000002 * 16.043) + (0.00000114 * 83.80) + (0.0000005 * 2.0159) + ( 0.0000005 * 44.0128) = 0.23 = 23% O by mass

The process by which hydrogen and oxygen combine to form water can be classified as Combination reaction.

A combination reaction is a reaction where two or more elements or compounds combine to form a single compound.

Such reactions are represented by equations of the following form :

X + Y → XY.

The combination of two or more elements to form one compound is called a combination reaction.

Therefore, The process by which hydrogen and oxygen combine to form water can be classified as Combination reaction.

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In the Lewis dot structure for nitrogen (N), the symbol is surrounded by five dots, representing its five valence electrons. Three of these are unpaired and available for bonding.

In the Lewis dot structure, the symbol for the element is surrounded by dots representing its valence electrons. Nitrogen (N) has five valence electrons. Therefore, in the Lewis dot structure for nitrogen, the symbol N, is surrounded by five dots.

There are three unpaired electrons and one electron pair in terms of bonding. The three unpaired electrons are available to form bonds with other atoms (most often seen in compounds like ammonia - NH3), while the pair of electrons remains as a lone pair on nitrogen in its compounds.

The Lewis dot symbol for nitrogen is a convenient way to visualize the valence electrons and helps predict the number of bonds formed by the element in its compounds.

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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: check explanation

Explanation:

Complete question: When liquid phosphorus trichloride is added to water, it reacts to form aqueous phosphorous acid, h3po3(aq), and aqueous hydrochloric acid. express your answer as a balanced chemical equation. Identify all the phases in your answer?

SOLITION:

The solution to the question we have here is to balance the chemical reaction. But before we do that, let us take some notes on one of the REACTANTS, Phosphorus trichloride. Phosphorus trichloride is also known as trichlorophosphine. Phosphorus trichloride is a yellow fuming liquid that has a pungent smell. The smell of Phosphorus trichloride is very similar to that of Hydrogen chloride.

Phosphorus trichloride has a molecular weight of 137.33 g/mol.

Phosphorus trichloride can react with water to form HP0(OH)2 with HCl or H3PO3 and HCl.

The balanced equations of Reaction are given below;

(1). PCl3 (l)+ 3H2O (l) --------> H3PO3 (aq) + 3HCl (aq).

(2). PCl3 (l) + 3H2O (l) ------> HPO(0H)2 (aq) + 3HCl (aq).

For the question, the reaction to use is the equation (1).

Phosphorus trichloride,PCl3 is in liquid phase, water,H2O is in liquid phase two( both reactants are in liquid phase).

H3PO4 are both in aqeous phase.

Final answer:

Liquid phosphorus trichloride reacts with water to form aqueous phosphorous acid and aqueous hydrochloric acid through hydrolysis, showcasing its application in producing phosphorous acid.

Explanation:

When liquid phosphorus trichloride (PCl3) is added to water, it reacts to form aqueous phosphorous acid, H3PO3(aq), and aqueous hydrochloric acid. This reaction is an example of hydrolysis, a chemical process by which a compound reacts with water, leading to the decomposition of the original compound and the formation of new compounds. In this particular reaction, the phosphorus trichloride undergoes hydrolysis to yield phosphorous acid and hydrochloric acid, as represented by the chemical equation PCl3(l) + 3H2O(l) → H3PO3(aq) + 3HCl(g). Phosphorous trichloride is thus a valuable precursor for generating phosphorous acid, a compound that finds application in various chemical syntheses and industries.

Answer:

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

Explanation:

just had this

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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The statement of element has the same number of valence electrons as phosphorus is "Bi."

The electrons present in an atom's outermost energy level, are known as valence electrons. The number of valence electrons in neutral atoms is equal to the main group number of the atom. Valence electrons have a higher energy than inner orbit electrons and therefore involved in the majority of chemical reactions. They help us figure out an element's chemical properties, such as its valency and how it forms bonds with other elements.

An atom with a closed valence electron shell is usually chemically inert. In the outermost energy orbitals, Group 5A elements have five valence electrons (ns2np3). Bismuth (Bi) is positioned in group 5, and hence does have the same number of valence electrons as phosphorus (P), which is 5, since they both belong to the nitrogen family. Rubidium, on the other hand, is an s-block element with one valence electron.

Hence the correct answer is Bi.

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