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3 years ago

What is the definition for exothermic and endothermic energy?

1 answer:

8 0

Exothermic- the word describes a process that releases energy in the form of heat. Forming a chemical bond releases energy and therefore is an exothermic process. Exothermicreactions usually feel hot because it is giving heat to you. Endothermic - a process or reaction that absorbs energy in the form of heat.

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One question for chem?? Image attached? please help ! :)

lana [24]

The only bond that involves the complete transfer of electrons is ionic bonding.

A metal that does not have much care for its electrons, such as Sodium, Na, is willing to give up its electron more freely. And an atom that really cares about having electrons might be a gas such as chlorine, Cl. The Chlorine atom takes the electron from Sodium, and then the newly formed ions of Na+ and Cl- bond because they have equal and opposite charges and opposites attract. NaCl is formed.

Hydrogen bonds aren’t actually real bonds (I know, the name is deceptive)

Covalent bonds involve the sharing of electrons.

I’m pretty sure metallic bonds is a made-up term.

7 0

3 years ago

What information is needed to calculate the average atomic mass of an element?(1 point)

g100num [7]

Answer:

Taking into account the definition of average atomic mass and isotopes of an element, the information that you need is the masses of its isotopes and their percent abundances.

Each chemical element is characterized by the number of protons in its nucleus, which is called the atomic number Z.

But in the nucleus of each element it is also possible to find neutrons, whose number can vary. The atomic mass (A) is obtained by adding the number of protons and neutrons in a given nucleus.

The same chemical element can be made up of different atoms, that is, their atomic numbers are the same, but the number of neutrons is different. These atoms are called isotopes of the element.

The atomic mass of an element is the weighted average mass of its natural isotopes. Therefore, the atomic mass of an element is not a whole number.

The weighted average means that not all isotopes have the same percentage.

In other words, the atomic masses of chemical elements are usually calculated as the weighted average of the masses of the different isotopes of each element, taking into account the relative abundance of each of them.

Explanation:

7 0

3 years ago

How many moles of NaCl are created as a result of decomposing 12 grams of NaClO3? (molar mass of Na=23, Cl=35, O=16)

Harman [31]

Answer: 0.113 moles of NaCl are created as a result of decomposing 12 grams of $NaClO_3$ .

Explanation:

To calculate the moles :

$\text{Moles of solute}=\frac{\text{given mass}}{\text{Molar Mass}}$

$\text{Moles of} NaClO_3=\frac{12g}{106.5g/mol}=0.113moles$

The balanced chemical equation for decomposition of $NaClO_3$ is:

$2NaClO_3\rightarrow 2NaCl+3O_2$

According to stoichiometry :

2 moles of $NaClO_3$ give = 2 moles of $NaCl$

Thus 0.113 moles of $NaClO_3$ give = $\frac{2}{2}\times 0.113=0.113moles$ of $NaCl$

Thus 0.113 moles of NaCl are created as a result of decomposing 12 grams of $NaClO_3$ .

8 0

3 years ago

Stearic acid (C18H36O2) is a fatty acid, a molecule with a long hydrocarbon chain and an organic acid group (COOH) at the end. I

Paha777 [63]

Answer:

There is 9671 Kj of heat released

Explanation:

Step 1: The balanced equation:

C18H36O2(s) + 26O2(g) --> 18CO2(g)+18H2O(g)

This means for 1 mole of C18H36O2 consumed there is 26 moles of O2 needed to produce 18 moles of CO2 and 18 moles of H2O.

Step 2: Calculate the heat of combustion

ΔH (combustion) = [18*(ΔHf of CO2) + 18*(ΔHf of H2O)] - [1*(ΔHf of C18H36O2) + 26*(ΔHf of O2)]

ΔH (combustion) = [18*(-394 kJ/mol) + 18*(-242 kJ/mol)] - [1*(-948 kJ/mol) + 26*(0 kJ/mol)]

ΔH (combustion) = [(-7092 kJ/mol) + (-4356 kJ/mol)] - (-948 kJ/mol)

= -10500 kJ/mol

ΔH (combustion) = heat released / number of moles of stearic acid

Step 3: Calculate moles of stearic acid

moles of stearic acid = mass / Molar mass of stearic acid

moles of stearic acid = 262g / 284.48 g/mole = 0.921 moles

Step 4: Calculate moles of oxygen

moles of O2 = 914.5 / 32g/mole

moles of O2 = 28.578125 moles

Stearic acid is the limiting reactant: it will completely react

There will react 26*0.921 mole = 23.946 mole of O2

This means there will remain 4.63 moles of O2

Step 5: Calculate heat released

q = (ΔH combustion) * (moles of stearic acid) = (-10500 kJ/mol) * (0.921 moles) = 9671 Kj

There is 9671 Kj of heat released

6 0

3 years ago

A) Calculate the molar mass of ethanol, C2H5OH and water, H20. C2H5OH = H2O = I

Mrrafil [7]

Answer:

1-46

2-18

Explanation:

c=12 H=1 O=16

ethanol (12×2)+(6×1)+(16)=46

water (2×1)+(16)=18

7 0

3 years ago