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Ulleksa [173]
3 years ago
8

What is the mass number of 207Pb ? A: 289 B: 207 C: 125 D: 82

Chemistry
1 answer:
Sergio [31]3 years ago
3 0
207 is the mass number. 82 would be the atomic number
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PLZ HELP For the reaction: 2NO2(g) → N2O4(l),
Furkat [3]

Answer: \Delta H_{rxn}=-20kJ/mol-(+66kJ/mol)

Explanation:

Heat of reaction or enthalpy change is the energy released or absorbed during the course of the reaction.

It is calculated by subtracting the enthalpy of reactants from the enthalpy of products.

\Delta H=H_{products}-H_{reactants}

\Delta H = enthalpy change = ?

H_{products} = enthalpy of products

H_{reactants} = enthalpy of reactants

For the given reaction :

2NO_2(g)\rightarrow N_2O_4(l)

\Delta H=H_{N_2O_4}-2\times H_{NO_2}

\Delta H=-20kJ/mol-(+66kJ/mol)

6 0
3 years ago
What is element Na in a periodic table
Bess [88]

Answer:

Sodium.  

Explanation:

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isotope is ²³Na.

7 0
3 years ago
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Why must every redox reaction involve an oxidizing agent and a reducing agent?
vagabundo [1.1K]

A reduced element (which gains electrons) and an oxidized element are required for redox reactions (gives electrons). It is not a redox reaction if we lack both of them (an element can not receive electrons if no element gives electrons and vice versa).

A reduced half and an oxidized half, which always occur together, make up redox processes. While the oxidized half experiences electron loss and an increase in oxidation number, the reduced half obtains electrons and the oxidation number declines. The mnemonic devices OIL RIG, which stand for "oxidation is loss" and "reduction is gain," are simple ways to memorize this. In a redox process, the total number of electrons stays constant. In the reduction half reaction, another species absorbs those that were released in the oxidation half reaction.

In a redox reaction, two species exchange electrons, and they are given unique names:

  • The ion or molecule that accepts electrons is called the oxidizing agent - by accepting electrons it oxidizes other species.
  • The ion or molecule that donates electrons is called the reducing agent - by giving electrons it reduces the other species.

Hence, what is oxidized is the reducing agent and what is reduced is the oxidizing agent.

<h3>What is the purpose of oxidizing agents and reducing agents?</h3>

By reducing other compounds and shedding electrons, a reducing agent raises its oxidation state. An oxidizing agent gets electrons by oxidizing other compounds; as a result, its oxidation state lowers.

<h3>What is a redox reaction?</h3>

Oxidation-reduction (or "redox") reactions are chemical processes in which electrons are exchanged between two substances. An oxidation-reduction reaction is any chemical process in which a molecule, atom, or ion alters the number of electrons it has, hence increasing or decreasing its oxidation state.

Learn more about redox reaction:  brainly.com/question/13293425

#SPJ4

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When Na2O is mixed with Mn(NO3)4 it forms NaNO3 and MnO2. We start with 25.0 g
coldgirl [10]
I don’t know what have you heard that with na20
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Which nuclear energy releases the most energy
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Fission and fusion Releases the most energy
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