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3 years ago

13. Which statement best describes an element? *

Chemistry

1 answer:

Natasha2012 [34]3 years ago

4 0

Explanation:

Distinguish chemical substances from mixtures

Key Points

Matter can be broken down into two categories: pure substances and mixtures. Pure substances are further broken down into elements and compounds. Mixtures are physically combined structures that can be separated into their original components.

A chemical substance is composed of one type of atom or molecule.

A mixture is composed of different types of atoms or molecules that are not chemically bonded.

A heterogeneous mixture is a mixture of two or more chemical substances where the various components can be visually distinguished.

A homogeneous mixture is a type of mixture in which the composition is uniform and every part of the solution has the same properties.

Various separation techniques exist in order to separate matter, including include distillation, filtration, evaporation and chromatography. Matter can be in the same phase or in two different phases for this separation to take place.

Terms

substanceA form of matter that has constant chemical composition and characteristic properties. It is composed of one type of atom or molecule.

elementA chemical substance that is made up of a particular kind of atom and cannot be broken down or transformed by a chemical reaction.

mixtureSomething that consists of diverse, non-bonded elements or molecules.

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Read 2 more answers

How many grams of zinc metal will react completely with 7.8 liters of 1.6 M HCl? Show all of the work needed to solve this probl

Andru [333]

Answer:

For 1: The correct answer is 407.97 grams.

For 2: The correct answer is 76.72 grams.

Explanation:

For 1:

We are given the molarity of HCl, to find the moles of HCl, we use the formula:

$Molarity=\frac{\text{Moles}{\text{Volume}}$

We are given:

Molarity = 1.6 M

Volume = 7.8 L

Putting values in above equation, we get:

$1.6mol/L=\frac{\text{Moles of HCl}}{7.8L}\\\\\text{Moles of HCl}=12.48mol$

For the given reaction:

$Zn(s)+2HCl(aq.)\rightarrow ZnCl_2(aq.)+H_2(g)$

By Stoichiometry of the reaction:

2 moles of HCl reacts with 1 mole of zinc metal.

So, 12.48 moles of HCl react with = $\frac{1}{2}\times 12.48=6.24mol$ of Zinc metal.

To calculate the mass of zinc metal, we use the formula:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

Molar mass of Zinc metal = 65.38 g/mol

$6.24=\frac{\text{Mass of zinc metal}}{65.38g/mol}\\\\\text{Mass of zinc metal}=407.97g$

For 2:

We are given that 298 grams of 83.1 % by mass of iron (II) nitrate solution are present.

So, mass of Iron (II) nitrate solution will be = $\frac{83.1}{100}\times 298=247.638g$

Molar mass Iron (II) nitrate = 180 g/mol

Putting values in equation 1, we get:

$\text{Moles of }Fe(NO_3)_2=\frac{247.638g}{180g/mol}=1.37mol$

For the following reaction:

$2Al(s)+3Fe(NO_3)_2(aq.)\rightarrow 3Fe(s)+2Al(NO_3)_3(aq.)$

By Stoichiometry of the reaction:

3 moles of $Fe(NO_3)_2$ produces 3 moles of iron metal.

So, 1.37 moles of $Fe(NO_3)_2$ will produce = $\frac{3}{3}\times 1.37=1.37mol$ of iron metal.

To calculate the mass of zinc metal, we equation 1:

$1.37=\frac{\text{Mass of iron metal}}{56g/mol}\\\\\text{Mass of iron metal}=76.72g$

5 0

3 years ago

How many moles of N2 are in a flask with a volume of 0.5 L at a pressure of 400.0 kPa and a temperature of 300.0 K?

mylen [45]

Answer:

0.08moles

Explanation:

Given parameters:

Volume of gas = 0.5L

Pressure of gas = 400kPa

Temperature of gas = 300K

Unknown:

Number of moles of N₂ = ?

Solution:

Applying the ideal gas law which is a combination of the three gas law: Boyle's law, Charles's law and Avogadro's law will solve this problem.

The ideal gas law is stated as;

PV = nRT

P is the pressure of the gas

V is the volume of the gas

n is the number of moles

R is the gas constant

T is the temperature of the gas

We need to convert kPa of the pressure to atm which is a more comfortable unit to work with.

400kPa will be $\frac{400}{101.325}$ = 3.95atm

Input the variables in the equation;

3.95 x 0.5 = n x 0.082 x 300

n = 0.08moles

5 0

3 years ago