Are new atoms made during a chemical reaction?

How many of the following are oxidation-reduction reactions? I. reaction of a metal with a nonmetal II. synthesis III. combustio

nadezda [96]

Answer : The oxidation-reduction reactions are:

I. reaction of a metal with a nonmetal

II. synthesis

III. combustion

Explanation :

Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.

Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.

Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.

I. Reaction of a metal with a nonmetal :

When sodium react with chlorine gas then it react to give sodium chloride.

$2Na+Cl_2\rightarrow 2NaCl$

In this reaction, the oxidation state of sodium changes from (0) to (+1) and shows oxidation and the oxidation state of chlorine changes from (0) to (-1) and shows reduction. So, It is an oxidation-reduction reaction.

II. Synthesis reaction :

A chemical reaction where multiple substances or reactants combine to form a single product.

When hydrogen react with oxygen then it react to give water.

$2H_2+O_2\rightarrow 2H_2O$

In this reaction, the oxidation state of hydrogen changes from (0) to (+1) and shows oxidation and the oxidation state of oxygen changes from (0) to (-2) and shows reduction. So, It is an oxidation-reduction reaction.

III. Combustion reaction :

A chemical reaction in which a hydrocarbon reaction with the oxygen to give product as carbon dioxide and water.

When methane react with oxygen gas then it react to give carbon dioxide and water.

$CH_4+2O_2\rightarrow CO_2+2H_2O$

In this reaction, the carbon of methane gain oxygen and shows oxidation and the oxygen gas gain hydrogen and shows reduction. So, It is an oxidation-reduction reaction.

IV. Precipitation reaction :

It is defined as the reaction in which an insoluble salt formed when two aqueous solutions are combined.

The insoluble salt that settle down in the solution is known an precipitate.

It is a double displacement reaction. So, it is not an oxidation-reduction reaction.

V. Decomposition reaction :

A chemical reaction in which the the larger molecule decomposes to give two or more smaller molecules.

The oxidation state remains same on reactant and product side. So, it is not an oxidation-reduction reaction.

3 0

3 years ago

In a heat engine, 700 J of heat enters the system, and the piston does 400 J of work. What is the final internal (thermal) energ

Vitek1552 [10]

The first law of thermodynamics characterises the two types of energy transfer, as heat and as thermodynamic. The final internal (thermal) energy of the system is 1,500 J.

<h3>What is internal energy?</h3>

The energy present in a system itself for conducting reactions is called internal energy.

Given,

Heat entering system (Q) = 700 J
Work done by the piston (W) = 400
Initial energy $(\rm U_{1})$ = 1200 J

According to the <u>first law of thermodynamics</u>:

$\rm Q = \Delta U + W$

Substituting values in the above equation:

$\begin{aligned}\rm Q &= \rm U_{2} - U_{1} + W\\\\\rm U_{2} &= \rm Q - W + U_{1}\\\\\rm U_{2} &= 700 - 400 + 1200\\\\&= 1500 \;\rm J\end{aligned}$

Therefore, option D. 1500 J is the final energy.

Learn more about internal energy here:

brainly.com/question/2602565

4 0

2 years ago

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When sodium is put in water, the metal floats on the surface and reacts to form sodium

mrs_skeptik [129]

Answer: Sodium also floats on the surface, but enough heat is given off to melt the sodium (sodium has a lower melting point than lithium and the reaction produces heat faster) and it melts almost at once to form a small silvery ball that dashes around the surface.

Explanation:

8 0

3 years ago

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How many atoms are in 5.2 moles of Na ?

Nastasia [14]

One mole of a substance is defined by Avogadro as consisting of 6.022 x 1023 atoms. This is Avogadro's number. To calculate the number of atoms in two moles of sodium, use dimensional analysis. 2.0 moles Na x 6.022⋅1023g1mol=1.20⋅1024 atoms of Na

8 0

3 years ago

In which cell structure does MOST of the process of cellular respiration take place?

ahrayia [7]

Mitochondria are rod-shaped organelles are basically considered the power producers of the cell, it converts oxygen and nutrients into adenosine triphosphate or ATP, which is the chemical energy,also known as "currency" of the cell which powers the metabolic actions of the cell. This process is called aerobic respiration and it is the reason animals breathe oxygen. Cellular repiration happens in the mitochodrion. The 3 phases of cellular respiration are Krebs Cycle, Electron Transport and Glycolysis (Fermentation). Glycolysis takes place in the cytoplasm while the Krebs cycle and electron transport take place in the mitochondria.

6 0

3 years ago