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3 years ago

Calculate ∆E for the following case:

Chemistry

1 answer:

NARA [144]3 years ago

5 0

Answer:

The internal energy(ΔE) of a substance is calculated below:

From the first law of thermodynamics;

ΔE=q+w

Explanation:

ΔE=q+w

here;

+q=endothermic reaction

-q=exothermic reaction

+w=work done on the system

-w=work done by the system

Given:

q=+1.62kJ=1620J

w=-874J

To solve:

the internal energy(ΔE)

We know:

ΔE=q+w

according to the problem;

ΔE=q-w

since;

w=-874J (i.e.)work is done by the system.

ΔE=1620-874

ΔE=+746J

Therefore the internal energy is +746J

i.e. the option is "c"(+746J)

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The following physical constants are for water, H2O.

Delicious77 [7]

Answer:

$Q\approx6.4~kJ$

Explanation:

Quantity of heat required by 10 gram of ice initially warm it from -5°C to 0°C:

$Q_1=m.C_s.\Delta T$

here;

mass, m = 10 g

specific heat capacity of ice, $C_s=2.09~J.g^{-1}.^{\circ}C^{-1}$

change in temperature, $\Delta T=(5-0)=5^{o}C$

$Q_1=10\times2.09\times 5$

$Q_1=104.5~J$

Amount of heat required to melt the ice at 0°C:

$Q_2=m.\Delta H_{fus}$

where, $\Delta H_{fus}=6020~J/mol$

we know that no. of moles is = (wt. in gram) $\div$ (molecular mass)

$Q_2=\frac{10}{18} \times 6020$

$Q_2=3344.44~J$

Now, the heat required to bring the water to 70°C from 0°C:

$Q_3=m.C_L.\Delta T$

specific heat of water, $C_L=4.18~J/g/^oC$

change in temperature, $\Delta T=(70-0)=70^oC$

$Q_3=10\times 4.18\times 70$

$Q_3=2926~J$

Therefore the total heat required to warm 10.0 grams of ice at -5.0°C to a temperature of 70.0°C:

$Q=Q_1+Q_2+Q_3$

$Q=104.5+3344.44+2926$

$Q=6374.94~J$

$Q\approx6.4~kJ$

8 0

3 years ago

Which of the following reagents is/are likely to be used to form the Britton–Robinson buffer solution used in the experiment?

Ierofanga [76]

Answer:

I. A polyprotic, weak acid

II. Na2HPO4

Explanation:

Buffer solutions are those that, upon the addition of an acid or base, are capable of reacting by opposing the part of the basic or acid component to keep the pH fixed.

Buffers consist of hydrolytically active salts that dissolve in water. The ions of these salts are combined with acids and alkalis. These hydrolytically active salts are the products that result from the reaction between weak acids and strong alkalis such as calcium carbonate (from carbonic acid and calcium hydroxide) or between strong acids and weak alkalis such as ammonium chloride (a from hydrochloric acid and ammonium hydroxide).

A buffer acid reacts when a weak acid or weak base is combined with its corresponding hydrolytic salt in a water solution, a buffer system called a buffer is formed. As in this case a weak polyrotic acid with Na2HPO4, which allows the solution to be maintained at a pH of 3.8 against small aggregate amounts of both acid and base, thus favoring the reaction at a pH of 3.8

A buffer system is not always appropriate, because the ions of some hydrolytic salts can, for example, damage organisms that come into contact with it.

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3 years ago

Sometimes the respiratory system and the cardiovascular system (the heart and blood vessels) are grouped as one system called th

tino4ka555 [31]

Answer:

The regrouping of the two systems affect the components because they either don't work together or other...

Explanation:

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3 years ago

Read 2 more answers

A chemist must prepare of hydrochloric acid solution with a pH of at . He will do this in three steps: Fill a volumetric flask a

Eva8 [605]

Answer:

1.7 mL

Explanation:

A chemist must prepare 550.0 mL of hydrochloric acid solution with a pH of 1.60 at 25 °C. He will do this in three steps: Fill a 550.0 mL volumetric flask about halfway with distilled water. Measure out a small volume of concentrated (8.0 M) stock hydrochloric acid solution and add it to the flask. Fill the flask to the mark with distilled water. Calculate the volume of concentrated hydrochloric acid that the chemist must measure out in the second step. Round your answer to 2 significant digits.

Step 1: Calculate [H⁺] in the dilute solution

We will use the following expresion.

pH = -log [H⁺]

[H⁺] = antilog - pH = antilog -1.60 = 0.0251 M

Since HCl is a strong monoprotic acid, the concentration of HCl in the dilute solution is 0.0251 M.

Step 2: Calculate the volume of the concentrated HCl solution

We want to prepare 550.0 mL of a 0.0251 M HCl solution. We can calculate the volume of the 8.0 M solution using the dilution rule.

C₁ × V₁ = C₂ × V₂

V₁ = C₂ × V₂/C₁

V₁ = 0.0251 M × 550.0 mL/8.0 M = 1.7 mL

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3 years ago

Describe the orbital notation and electron configuration notation to describe the placement of all of the electrons in an atom o

andriy [413]

The arrangement of the electrons on the orbitals is governed by the principles of quantum energy. To be able to draw the correct electronic configuration of an element, they should follow these three principles.

1. Aufbau's Principle. The electrons of an element should be filled up from the highest energy level. You can use the periodic table as a guide for this. In decreasing order, the energy of the orbitals are 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d and 7p. Each 'box' of these orbital must be filled with two electrons from 1s before moving on to the next.

2. Hund's rule. This states that you must fill all boxes of one orbital with one electron first. For example, 2p has 3 boxes. You fill one electron for each box first before going back to fill it to two electrons if there are still excess.

3. Pauli's Exclusion Principle. This states that no electrons of the same element should have the same quantum numbers. To achieve this, the two electrons in each box should have opposite spins, one facing up, and the other facing down.

Using these three rules, you will be able to draw the electronic configuration of Fluorine with 9 electrons as shown in the picture.

7 0

3 years ago