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sleet_krkn [62]
2 years ago
11

A sample of water is cooled from 45°C to 35°C by the removal of 84 Joules of heat. What is

Chemistry
1 answer:
muminat2 years ago
4 0

Answer:

m = 2 g

Explanation:

Given data:

Initial temperature = 45°C

Final temperature = 35°C

Heat evolved = 84 j

Mass of water = ?

Solution:

Formula:

Q = m.c. ΔT

Q = amount of heat absorbed or released

m = mass of given substance

c = specific heat capacity of substance

ΔT = change in temperature

specific heat capacity of water is 4.18 J/g.°C

ΔT = 35°C - 45°C

ΔT = - 10°C

84 j = m ×4.18 J/g.°C ×- 10°C

84 j = m × -41.8 J/g

m = 84 j / -41.8 J/g

m = 2 g

negative sign shows heat is evolved.

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4 0
3 years ago
Why does hot water freeze faster than cold water?
weeeeeb [17]
<h2>Answer:</h2>

<u>Temperature dependency is responsible for the process that hot water freeze faster than cold water.</u>

<h2>Explanation:</h2>

The effect given above is called Mpemba Effect. According to this idea hot water freezes more quickly as compared to cold water. But until now there is no convincing explanation for this strange phenomenon.  One idea is that hot containers make better thermal contact with a refrigerator and so conduct heat more efficiently because a good conductor is good fro the transfer of heat. Another idea about this effect is that warm water evaporates more quickly and since this is an endothermic process, it cools the water making it freeze more quickly.

7 0
3 years ago
Read 2 more answers
Complete the balanced neutralization equation
lbvjy [14]

Answer:

2 HC₂H₃O₂(aq) + Sr(OH)₂(aq) ⇒ Sr(C₂H₃O₂)₂(aq) + 2 H₂O

Explanation:

Let's consider the reaction between acetic acid and strontium hydroxide. This is a neutralization reaction, in which an acid reacts with a base to form salt and water. The unbalanced equation is:

HC₂H₃O₂(aq) + Sr(OH)₂(aq) ⇒ Sr(C₂H₃O₂)₂(aq) + H₂O

We have 1 acetate ion to the left and 2 to the right, so we will multiply HC₂H₃O₂(aq) by 2.

2 HC₂H₃O₂(aq) + Sr(OH)₂(aq) ⇒ Sr(C₂H₃O₂)₂(aq) + H₂O

Finally, we multiply water by 2 to get the balanced equation.

2 HC₂H₃O₂(aq) + Sr(OH)₂(aq) ⇒ Sr(C₂H₃O₂)₂(aq) + 2 H₂O

8 0
3 years ago
Four properties of water are listed. It reacts with halogens to form oxygen gas as one of the products. It is transparent and ta
Bezzdna [24]

Chemical property is the property of the substances that describes the ability of the substance to involve in chemical reactions. Physical property is that which does not change the chemical composition of the substances. The following properties of water that it is transparent and tasteless in its pure form and it freezes at a temperature of 0^{0}C are physical properties as they simply indicate the change in physical state without any change in chemical composition of water.

The other two properties that water reacts with halogens to form oxygen gas as one of the products and water decomposes to form hydrogen and oxygen are chemical properties as the chemical composition of water changes in the given reaction.

Therefore the correct answer is b. 1 and 4

8 0
3 years ago
What is the E°cell for the cell represented by the combination of the following half-reactions? ClO4–(aq) + 8H+(aq) + 8e– Cl–(aq
Vinvika [58]

Answer:

The E°cell for the cell represented by the combination of the given half-reactions is 0.398 V

Explanation:

Oxide-reduction reactions, also called redox, involve the transfer or transfer of electrons between two or more chemical species. In these reactions two substances interact: the reducing agent and the oxidizing agent.

The gain of electrons is called reduction and the loss of electrons oxidation. That is to say, there is oxidation whenever an atom or group of atoms loses electrons (or increases its positive charges) and in the reduction an atom or group of atoms gains electrons, increasing its negative charges or decreasing the positive ones.

The species that supplies electrons is the reducing agent (that is, it is that species that oxidizes, yielding electrons and increasing its positive charge, or decreasing the negative one causing the reduction of the other species) and the one that gains them is the oxidizing agent ( that is, it is that species that is reduced, capturing electrons and increasing its negative charge, or decreasing its positive charge, causing oxidation of the other species).

This is the type of reaction that occurs in this case.

ClO₄⁻(aq) + 8 H⁺ (aq) + 8 e⁻ ⇔ Cl⁻ (aq) + 4 H₂O(l) E° = 1.389 V

VO₂⁺(aq) + 2 H⁺(aq) + e⁻ ⇔ VO⁺(aq) + H₂O(l) E° = 0.991 V

In this case both are written as reductions, and their E ° values ​​as well. The species that has the greatest potential for reduction will be the species that will be reduced, that is, it will be the oxidizing agent. In this case, it will be the first half-reaction expressed.  Therefore, to obtain a reaction, the second semi-reaction must be reversed to be an oxidation, maintaining its constant value. Then:

Reduction: ClO₄⁻(aq) + 8 H⁺ (aq) + 8 e⁻ ⇔ Cl⁻ (aq) + 4 H₂O(l) E° = 1.389 V

Oxidation: VO⁺(aq) + H₂O(l) ⇔ VO₂⁺(aq) + 2 H⁺(aq) + e⁻ E° = 0.991 V

<em>E°cell=Ereduction - Eoxidation</em>

E°cell=1.389 V - 0.991 V

<em>E°cell=0.398 V</em>

Then <u><em>the E°cell for the cell represented by the combination of the given half-reactions is 0.398 V.</em></u>

Another way of thinking is that, by inverting the second semi-reaction to be an oxidation, the value of E ° is reversed in the sign, unlike the previous case in which it was constant. Then:

Reduction: ClO₄⁻(aq) + 8 H⁺ (aq) + 8 e⁻ ⇔ Cl⁻ (aq) + 4 H₂O(l) E° = 1.389 V

Oxidation: VO⁺(aq) + H₂O(l) ⇔ VO₂⁺(aq) + 2 H⁺(aq) + e⁻ E° = -0.991 V

In this case:

E°cell=Ereduction + Eoxidation=

E°cell=1.389 V + (-0.991 V)=1.389 V-0.991 V

<em>E°cell=0.398 V</em>

Note that the result obtained is the same. This indicates that either of the two ways proposed is correct, and you will use the one that is most comfortable for you.

4 0
3 years ago
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