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3 years ago

Aluminum is an element. Which best describes what makes up a sample of aluminum?

Chemistry

2 answers:

Ksivusya [100]3 years ago

8 0

Answer:

One kind of atom.

Step-by-step explanation:

An element consists of one kind of atom.

Al is an element, so Al consists of one kind of atom.

C and D are wrong , because Al contains only atoms of aluminium.

Alinara [238K]3 years ago

3 0

Answer: one kind of atom

Explanation:

Element is a pure substance which is composed of similar atoms.It can not be decomposed into simpler constituents using chemical reactions.Example: Aluminium $Al$

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: water $H_2O$

Thus as aluminium is made up of one kind of atom , it is considered as an element.

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Use bond enthalpy values to calculate the enthalpy change for the following reaction. Then, label if the reaction is endothermic

Mila [183]

Based on the bond energies given, the enthalpy change for the reaction of is -33 kJ and the reaction is exothermic.

<h3>What is the change in bond energy of a reaction?</h3>

The change in bond energy of a reaction is calculated using the formula below:

change in bond energy = sum of energies of bonds broken - sum of energies of bonds formed

A reaction is exothermic if the change in bond energy is negative.

A reaction is endothermic if the change in bond energy is positive.

Given the bond enery values above:

sum of energies of bonds broken = 4 × C-H + Br-Br

sum of energies of bonds broken = 4 × 413 + 193 = 1845 kJ

sum of energies of bonds formed = 3 × C-H + C-Br + H-Br

sum of energies of bonds formed = 3 × 413 + 276 + 363 = 1878 kJ

Thus;

change in bond energy = 1845 - 1878 = -33 kJ

The reaction is exothermic because the change in bond energy is negative.

Therefore, the enthalpy change for the reaction of is -33 kJ and the reaction is exothermic.

Learn more about enthalpy change at: brainly.com/question/11628413

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2 years ago

At elevated temperatures, molecular hydrogen and molecular bromine react to partially form hydrogen bromide:

gayaneshka [121]

Answer: The moles of bromine gas at equilibrium is 0.324 moles.

Explanation:

To calculate the molarity of solution, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}$ .......(1)

Calculating the initial moles of hydrogen and bromine gas:

For hydrogen gas:

Moles of hydrogen gas = 0.682 mol

Volume of solution = 2.00 L

Putting values in equation 1, we get:

$\text{Molarity of solution}=\frac{0.682mol}{2.00L}=0.341M$

For bromine gas:

Moles of bromine gas = 0.440 mol

Volume of solution = 2.00 L

Putting values in equation 1, we get:

$\text{Molarity of solution}=\frac{0.440mol}{2.00L}=0.220M$

Now, calculating the molarity of hydrogen gas at equilibrium by using equation 1:

Equilibrium moles of hydrogen gas = 0.566 mol

Volume of solution = 2.00 L

Putting values in equation 1, we get:

$\text{Molarity of solution}=\frac{0.566mol}{2.00L}=0.283M$

Change in concentration of hydrogen gas = 0.341 - 0.283 = 0.058 M

This change will be same for bromine gas.

Equilibrium concentration of bromine gas = $(\text{Initial concentration}-\text{Change in concentration})=0.220-0.058=0.162M$

Now, calculating the moles of bromine gas at equilibrium by using equation 1:

Molarity of bromine gas = 0.162 M

Volume of solution = 2.00 L

Putting values in equation 1, we get:

$0.162M=\frac{\text{Moles of bromine gas}}{2.00L}\\\\\text{Moles of bromine gas}=(0.162mol/L\times 2.00L)=0.324mol$

Hence, the moles of bromine gas at equilibrium is 0.324 moles.

5 0

3 years ago