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3 years ago

describe the difference between a physical and chemical change explain what happens during a checmical reaction

Chemistry

1 answer:

Over [174]3 years ago

7 0

Explanation:

A physical change is a change that alters the physical properties of matter particularly the form and state.

In many cases the change is easily reversible. Examples are changes of state such as freezing, boiling, melting e.t.c

A chemical change is a change in which a new kind of matter is formed. It is always accompanied by energy changes which can either be evolution or absorption of heat or light or both.

The process is not easily reversible. Examples are combustion, rusting of iron, precipitation, e.t.c

During a chemical reaction, the reactants undergo a chemical change.

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How many moles are there in 45.6 grams of yttrium?

leva [86]

Number of moles = mass/ molar mass
= 45.6g / 88.90g/mol
= 0.512 moles

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3 years ago

What does c3h8 equal

Svetradugi [14.3K]

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3 years ago

Which term below represents a pure substance that can be separated chemically but cannot be separated physically that is made up

Nastasia [14]

C.molecules- made up of more than one atom and can only be broken by chemical means

8 0

3 years ago

Please please help!

ratelena [41]

The mass percent of potassium chloride is 1.386%

calculation

mass percent = actual mass/ Theoretical mass x 100

Actual mass = 9.35 g

Theoretical mass is calculated as below

Step 1 : write the equation for reaction

KCl + H₂O → KOH + HCl

Step 2: find the moles of H₂O

moles = mass÷ molar mass

The molar mass of H₂O = (2 x1 ) +(16) = 18 g/mol

moles is therefore = 162.98 g÷ 18 g/mol =9.054 moles

Step 3: use the mole ratio to determine the moles of KCl

KCl: H₂O is 1:1 therefore the moles of KCl is also = 9.054 moles

Step 4: find the theoretical mass of KCl

mass = moles x molar mass

from periodic table the molar mass of KCl = 39 +35.5 =74.5 g/mol

mass = 9.054 moles x 74.5 g/mol =674.5 g

Theoretical mass is therefore = 9.35 g/ 674.5 g x 100 = 1.386%

3 0

4 years ago

Different phases of water have different densities. True or false?

Art [367]

Answer: True

Explanation:

Indeed, different phases of water have diffferent densities.

The different phases, solid, liquid, and gas, of water are characterized by the separation of the molecules.

The density is a measure of concentration of the mass of a substance. Mathematically, density is the ratio of the mass to the volume:

density = mass / volume

A high density means a high ratio of mass to volume, and a low density means a low ratio of mass to volume.

The volume is the space occupied by the substance and the space occupied is related to the separation among the particles (atoms, molecules or ions).

Since, each state is characterized by certain separation of the particles, you can conclude that the different phases of water have different densities.

The densities of the gases are low and highly dependent on the temperature and pressure. So, the water vapor is the phase with the lowest densities.

Liquid water in the range of 5°C - 100°C has densities in the range 0.9998°C to 0.9587 g/cm³.

The density of water at 4 °C (liquid phase) is 1.000 g/cm³.

Due to the special interactions of hydrogen bonds, the density of water starts to decrease at temperatures below 4 °C ( 0.9999 g/cm³ - 0.9839 g/cm³), causing the frozen water (ice) to be less dense and float in the water.

5 0

3 years ago