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Paladinen [302]
3 years ago
8

A student carefully drops a 9.0 g solid Zn pellet initially at 50.0°C into an insulated cup containing 30.0 g of water at 27.8°C

. The student predicts that the temperature of the water will increase after the pellet is added. Which of the following statements is the best justification for the student's prediction? (A) The metallic bonds between Zn atoms will break when the Zn is exposed to the water molecules, releasing energy that will be absorbed by the water molecules. (B) Collisions between the water molecules and the surface of the Zn pellet will result in the transfer of energy, increasing the average kinetic energy of the water molecules. (C) The strength of the hydrogen bonds between the water molecules will increase when the Zn pellet is added, decreasing the average kinetic energy of the water molecules. (D)Collisions between Zn atoms in the solid will increase in frequency when the Zn is exposed to the water molecules, resulting in the transfer of energy to the surroundings.
Chemistry
2 answers:
melisa1 [442]3 years ago
6 0

Answer:

(B) Collisions between the water molecules and the surface of the Zn pellet will result in the transfer of energy, increasing the average kinetic energy of the water molecules.

Explanation:

The question above shows a case of energy transfer and movement of molecules in the generation of heat. Which can be explained as follows:

As you can see, in the question, the solid Zn pellet has a higher temperature than water. There is a physical concept that states that when two bodies of different temperatures come into contact, there is a transfer of energy between them that seeks to equal the temperature of the two bodies. For this reason, when the Zn pellet comes into contact with water, collisions will occur between the water molecules and the surface of the Zn sediment that will result in energy transfer.

However, instead of causing the temperature balance between the water and the Zn tablet, this allows the water to get a higher temperature, because the energy transmitted by zinc increases the kinetic energy of the water molecules. In this case, these tomboys start to move very fast, generating heat.

jekas [21]3 years ago
3 0

Answer: choice B

Explanation: Heat flows from high to low. After you convert the Celsius into kelvin the Zn pellet has 323K and the water has 301K which results the transfer of the heat energy of the pallet to the water. ( you don’t have to convert, but it just make it easier) hope this helped you :)

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Which of the following solutions contains the greatest number of ions?
Elden [556K]

Answer : The correct option is, (A) 300.0 mL of 0.10 M CaCl₂

Explanation :

<u>(a) 300.0 mL of 0.10 M CaCl₂</u>

The dissociation reaction will be:

CaCl_2(aq)\rightarrow Ca^{2+}(aq)+2Cl^-(aq)

To calculate the number of moles of CaCl₂ as :

\text{Moles of }CaCl_2=\text{Concentration of }CaCl_2\times \text{Volume of solution in L}

\text{Moles of }CaCl_2=0.10M\times 0.3L=0.03mol

As, 1 mole of CaCl₂ contains ions = 3

So, 0.03 mole of CaCl₂ contains ions = 0.03 × 3 = 0.09 ions.

<u>(b) 400.0 mL of 0.10 M NaCl</u>

The dissociation reaction will be:

NaCl(aq)\rightarrow Na^{+}(aq)+Cl^-(aq)

To calculate the number of moles of NaCl as :

\text{Moles of }NaCl=\text{Concentration of }NaCl\times \text{Volume of solution in L}

\text{Moles of }NaCl=0.10M\times 0.4L=0.04mol

As, 1 mole of NaCl contains ions = 2

So, 0.04 mole of NaCl contains ions = 0.04 × 2 = 0.08 ions.

<u>(c) 200.0 mL of 0.10 M FeCl₃</u>

The dissociation reaction will be:

FeCl_3(aq)\rightarrow Fe^{3+}(aq)+3Cl^-(aq)

To calculate the number of moles of FeCl₃ as :

\text{Moles of }FeCl_3=\text{Concentration of }FeCl_3\times \text{Volume of solution in L}

\text{Moles of }FeCl_3=0.10M\times 0.2L=0.02mol

As, 1 mole of FeCl₃ contains ions = 4

So, 0.02 mole of FeCl₃ contains ions = 0.02 × 4 = 0.08 ions.

<u>(d) 800.0 mL of 0.10 M sucrose</u>

The dissociation of sucrose is not possible because it is a non-electrolyte.

To calculate the number of moles of sucrose as :

\text{Moles of }sucrose=\text{Concentration of }sucrose\times \text{Volume of solution in L}

\text{Moles of }sucrose=0.10M\times 0.8L=0.08mol

As, 1 mole of sucrose contains ions = 1

So, 0.08 mole of sucrose contains ions = 0.08 × 1 = 0.08 ions.

Hence, the solutions contains the greatest number of ions is, 300.0 mL of 0.10 M CaCl₂

3 0
3 years ago
A radioactive isotope of potassium (k) has a half-life of 20 minutes. if a 43 gram sample of this isotope is allowed to decay fo
Ksenya-84 [330]

Hello!

The half-life is the time of half-disintegration, it is the time in which half of the atoms of an isotope disintegrate.

We have the following data:

mo (initial mass) = 43 g

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x (number of periods elapsed) = ?

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Let's find the number of periods elapsed (x), let us see:

T = x*P

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80 = 20\:x

20\:x = 80

x = \dfrac{80}{20}

\boxed{x = 4}

Now, let's find the final mass (m) of this isotope after the elapsed time, let's see:

m =  \dfrac{m_o}{2^x}

m =  \dfrac{43}{2^{4}}

m = \dfrac{43}{16}

\boxed{\boxed{m = 2.6875\:g}}\end{array}}\qquad\checkmark

I Hope this helps, greetings ... DexteR! =)

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