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3 years ago

Which process is exothermic?

Chemistry

2 answers:

Sav [38]3 years ago

5 0

Answer: c. condensation of ethanol vapor

Explanation: An endothermic reaction is a type of of chemical reaction in which energy is absorbed from the surrounding. The temperature of the surrounding decreases.

An Exothermic reaction is a type of of chemical reaction in which energy is released into the surrounding. The temperature of the surrounding increases.

a.boiling of water: This involves conversion of liquid to gas and thus require energy and is endothermic.

b.melting of copper: This involves conversion of solid to liquid and thus require energy and is endothermic.

c. condensation of ethanol vapor: This involves conversion of vapor to liquid and thus release energy and is exothermic.

d.sublimation of iodine: This involves conversion of solid to gas and thus require energy and is endothermic.

valkas [14]3 years ago

4 0

The exothermic process is a process or reaction that involves a release of energy from the system to its surroundings in various forms usually through heat, light, electricity or sound. In the four given choices, when melting a copper, you try to immerse the metal in heaping coals of fire. The metal will absorb the thermal energy coming from the coal, thus, once you retrieve the metal back, light will be emitted from it as well as heat.

Therefore, the answer is B. MELTING OF COPPER

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What is the number of electron and neutron protons in atom 35?

Fittoniya [83]

The mass number = protons + neutrons. Bromine has a mass number of 80 and 35 protons so 80-35 = 45 neutrons. b) How many electrons does the neutral atom of bromine have? The neutral atom of bromine has 35 electrons because the number of electrons equals the number of protons.

6 0

3 years ago

What particle decay is this? 210 83 Bi→210 84 Po

sesenic [268]

Answer:

Beta emission

Explanation:

In beta emission, a neutron is converted into a proton thereby emitting an electron and a neutrino. A neutrino is a particle that serves to balance the spins.

When a nucleus undergoes beta emission, the mass number of the parent and daughter nuclei remain the same while the atomic number of the daughter nucleus is greater than that of its parent by one unit.

Hence, in beta emission, the daughter nucleus is found one pace to the right of the parent in the periodic table.

3 0

3 years ago

Phenolphthalein has a pKa of 9.7 and is colorless in its acid form and pink in its basic form. calculate [In-}/{HIn} for the fol

zvonat [6]

Answer:

1.58x10⁻⁵

2.51x10⁻⁸

0.0126

63.10

Explanation:

Phenolphthalein acts like a weak acid, so in aqueous solution, it has an acid form HIn, and the conjugate base In-, and the pH of it can be calculated by the Handerson-Halsebach equation:

pH = pKa + log[In-]/[HIn]

pKa = -logKa, and Ka is the equilibrium constant of the dissociation of the acid. [X] is the concentrantion of X. Thus,

i) pH = 4.9

4.9 = 9.7 + log[In-]/[HIn]

log[In-]/[HIn] = - 4.8

[In-]/[HIn] = $10^{-4.8}$

[In-]/[HIn] = 1.58x10⁻⁵

ii) pH = 2.1

2.1 = 9.7 + log[In-]/[HIn]

log[In-]/[HIn] = -7.6

[In-]/[HIn] = $10^{-7.6}$

[In-]/[HIn] = 2.51x10⁻⁸

iii) pH = 7.8

7.8 = 9.7 + log[In-]/[HIn]

log[In-]/[HIn] = -1.9

[In-]/[HIn] = $10^{-1.9}$

[In-]/[HIn] = 0.0126

iv) pH = 11.5

11.5 = 9.7 + log[In-]/[HIn]

log[In-]/[HIn] = 1.8

[In-]/[HIn] = $10^{1.8}$

[In-]/[HIn] = 63.10

6 0

3 years ago

The following thermochemical equation is for the reaction of nitrogen(g) with oxygen(g) to form nitrogen dioxide(g). N2(g) + 2O2

Rzqust [24]

Answer: The mass of nitrogen gas reacted to produce given amount of energy is 5.99 grams.

Explanation:

The given chemical reaction follows:

$N_2(g)+2O_2(g)\rightarrow 2NO_2(g);\Delta H=66.4kJ$

We know that:

Molar mass of nitrogen gas = 28 g/mol

We are given:

Enthalpy change of the reaction = 14.2 kJ

To calculate the mass of nitrogen gas reacted, we use unitary method:

When enthalpy change of the reaction is 66.4 kJ, the mass of nitrogen gas reacted is 28 grams.

So, when enthalpy change of the reaction is 14.2 kJ, the mass of nitrogen gas reacted will be = $\frac{28}{66.4}\times 14.2=5.99g$

Hence, the mass of nitrogen gas reacted to produce given amount of energy is 5.99 grams.

8 0

3 years ago

A student is using a coffee-cup calorimeter to determine the enthalpy change of the endothermic reaction of two aqueous solution

Liula [17]

Answer:

See the answer below

Explanation:

First, it should be understood that an endothermic reaction is one that absorbs energy in the form of heat from the surrounding. The products of endothermic reactions usually have higher energy than their reactants. Hence, the ΔH° which is referred to as the enthalpy change is usually positive.

Forgetting to cover the coffee-cup calorimeter means some of the heat energy absorbed by the reactants would be exchanged back to the surroundings - a loss. It also means that the enthalpy change would be smaller compared to if the cup had been covered because some of the heat has been lost to the surrounding.

8 0

3 years ago