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Trava [24]
3 years ago
9

State whether the following is an example of a physical or chemical change:! 21. Burning a log: ________________________________

! 22. Folding a piece of paper: _________________________! 23. Freezing water: _________________________! 24. Bending a copper wire. _________________________!
Chemistry
2 answers:
lyudmila [28]3 years ago
6 0

Answer:

Physical change

Explanation:

Because it doesn't require any chemical to change

Ivan3 years ago
5 0

Answer:

Physical change

Physical change

Physical change

Physical change

Explanation:

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Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one letter
maksim [4K]

Answer : The only reaction (C) that shows that the same reactant undergoes both oxidation and reduction.

Explanation :

Disproportionation reaction : It is defined as the reaction in which the same reactant undergoes both oxidation and reduction reaction. It is a redox reaction.

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.

(A) The given balanced reaction is,

H_2SeO_4(aq)+2Cl^-(aq)+2H^+(aq)\rightarrow H_2SeO_3(aq)+Cl_2(g)+H_2O(l)

This reaction is a redox reaction but not disproportionation reaction because in this reaction there are two reactants in which chlorine shows oxidation and selenium shows reduction.

(B) The given balanced reaction is,

S_8(s)+8O_2(g)\rightarrow 8SO_2(g)

This reaction is a redox reaction but not disproportionation reaction because in this reaction there are two reactants in which sulfur shows oxidation and oxygen shows reduction.

(C) The given balanced reaction is,

3Br_2(aq)+6OH^-(aq)\rightarrow 5Br^-(aq)+BrO_3^-(aq)+3H_2O(l)

This reaction is a disproportionation reaction because in this reaction only one reactant bromine that shows both oxidation and reduction reaction.

(D) The given balanced reaction is,

Ca^{2+}(aq)+SO_4^{2-}(aq)\rightarrow CaSO_4(s)

This reaction is a combination reaction in which the two reactant react to give a single product. There is no changes in the oxidation state of calcium and sulfate.

(E) The given balanced reaction is,

PtCl_4(s)+2Cl^-(aq)\rightarrow PtCl_6^{2-}(aq)

This reaction is a combination reaction in which the two reactant react to give a single product. There is no changes in the oxidation state of platinum and chlorine.

Hence, the only reaction (C) that shows that the same reactant undergoes both oxidation and reduction.

6 0
3 years ago
What mass of silver ag which has an atomic mass of 107.87 amu contains the same number of atoms contained in 10.0g of boron b wh
Masteriza [31]

To contain the same number of atoms also mean to contain the same number of moles. So let us say that X is the mass of Silver Ag required, so that:

X / 107.87 = 10 / 10.81

<span>X = 99.79 g</span>

6 0
3 years ago
Read 2 more answers
What is the balanced chemical equation when an aqueous solution of calcium hydroxide reacts with liquid water?
Dmitrij [34]

Explanation:

Equation for Calcium Hydroxide Dissolving in Water | Ca(OH)2 + H2O

7 0
3 years ago
How many atoms are in 6.3 moles of lead
densk [106]

Answer:

3.79 x 10²⁴atoms

Explanation:

Given parameters:

Number moles of lead  = 6.3moles

Unknown:

Number of atoms  = ?

Solution:

To solve this problem,

              1 mole of a substance contains  6.02 x 10²³ atoms

            6.3 mole of Pb  will contain 6.3  x 6.02 x 10²³ = 3.79 x 10²⁴atoms

4 0
3 years ago
Photosynthesis was another biological phenomenon that occupied the attention of the chemists of the late 18th century. The demon
balu736 [363]

Answer:

In the 1770s, the English clergyman Joseph Priestley (who is credited with the discovery of O2) established the production of oxygen by vegetables recognizing that the process was, apparently, the inverse of animal respiration, which consumed such chemical element.

Explanation:

In 1772, Joseph Priestley in his Recherches sur diversces especes d'air differentiated the air of animal respiration from that emitted by vegetables in the presence of light. Of the latter, which he called "dephlogistic air", he highlighted his purifying property of the environment indicating that: plants far from affecting the air in the same way as animal respiration, produce the opposite effects, and tend to preserve the sweet and healthy atmosphere , when it becomes harmful as a result of the life and breathing of the animals or their death and their rot.

In 1780, Jean Ingeshousz in his Experiences sur les vegetaux completed and reaffirmed the observations of Joseph Priestley. At the same time, he could deny Charles Bonnet's hypothesis, by demonstrating that the air expelled from the leaves comes from inside, and that the stimulating factor of the gaseous emission was not the heat produced by the sun, but the intensity of the light .

It was, finally, Jean Senebier that between 1782 and 1784, found that the "fixed air" dissolved in the water favors the vegetation. From these observations, he hypothesized that "fixed air" (carbon dioxide) is absorbed by the plants, which take it from the atmosphere with the humidity it has and in which it is mixed. Once this gas has been captured, both from the atmosphere and from the ground, it is decomposed in the presence of light by the leaves, releasing the "vital air" (oxygen) and leaving the carbon in the plant.

Thus, at the end of the century the participation of the atmosphere in plant dynamics was already seated, although the how and why of this participation were still unknown and no theory had been formulated to explain the nutritional process as a whole.

3 0
3 years ago
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