Answer:
Substances can change phase—often because of a temperature change. At low temperatures, most substances are solid; as the temperature increases, they become liquid; at higher temperatures still, they become gaseous.
The process of a solid becoming a liquid is called melting. (an older term that you may see sometimes is fusion). The opposite process, a liquid becoming a solid, is called solidification. For any pure substance, the temperature at which melting occurs—known as the melting point—is a characteristic of that substance. It requires energy for a solid to melt into a liquid. Every pure substance has a certain amount of energy it needs to change from a solid to a liquid. This amount is called the enthalpy of fusion (or heat of fusion) of the substance, represented as ΔHfus. Some ΔHfus values are listed in Table 10.2 “Enthalpies of Fusion for Various Substances”; it is assumed that these values are for the melting point of the substance. Note that the unit of ΔHfus is kilojoules per mole, so we need to know the quantity of material to know how much energy is involved. The ΔHfus is always tabulated as a positive number. However, it can be used for both the melting and the solidification processes as long as you keep in mind that melting is always endothermic (so ΔH will be positive), while solidification is always exothermic (so ΔH will be negative).
A sample of helium has a temperature of 450 K. The gas is cooled to 248.9 K at which time the gas occupies 103.4 L? Assume pressure is constant at 3 atm. What was the original volume of the gas?
A. 186.94 L
B. 304.5 L
C. 57.19 L
D. 361.07 L
Answer:
[tex]\boxed {\boxed {\sf A. \ 186.94 \ L}}[/tex]
Explanation:
We are asked to find the original volume of a gas given a change in temperature. Since pressure remains constant, we are only concerned with volume and temperature, so we use Charles's Law. This states the volume of a gas is directly proportional to the temperature. The formula for this law is:
[tex]\frac {V_1}{T_1}= \frac{V_2}{T_2}[/tex]
The gas begins with a temperature of 450 Kelvin, but the volume is unknown.
[tex]\frac {V_1}{450 \ K }= \frac{V_2}{T_2}[/tex]
The gas is cooled to 248.9 Kelvin and the gas occupies a volume of 103.4 liters.
[tex]\frac {V_1}{450 \ K }= \frac{103.4 \ L}{248.9 \ K}[/tex]
Since we are solving for the original volume, we must isolate the variable V₁. It is being divided by 450 Kelvin. The inverse operation of division is multiplication, so we multiply both sides of the equation by 450 K.
[tex]450 \ K \frac {V_1}{450 \ K }= \frac{103.4 \ L}{248.9 \ K}* 450 \ K[/tex]
[tex]V_1= \frac{103.4 \ L}{248.9 \ K}* 450 \ K[/tex]
The units of Kelvin cancel.
[tex]V_1= \frac{103.4 \ L}{248.9 }* 450[/tex]
[tex]V_1= 0.4154278827 \ L *450[/tex]
[tex]V_1= 186.9425472 \ L[/tex]
Round to the nearest hundredth. The 2 in the thousandths place tells us to leave the 4 in the hundredth place.
[tex]V_1 \approx 186.94 \ L[/tex]
The original volume is approximately 186.94 liters and Choice A is correct.
If an atom of chlorine (CI) were to ionize, it would
electron(s).
Answer:
Explanation:
As per being a Group 7 element, it would gain one electron, which changes it's charge to 1-. It is therefore negatively charged, having a full outer shell of 8, having its electronic structure to be at 2,8,8.
What general term is used to describe the pure liquid (such as a pure water) obtained in such a process
What’s the name of this compound?
What do the solid white and red balls in this model represent?
H
H— — О
A. Planets and
the Sun
B. Electrons
C. Molecules
D. Atoms
PREVIOUS
Answer:
C. Molecules
Explanation: Water is a compound that conatins molecules hydrogen and oxygen.
Answer: Atoms
Explanation:
precautive measures taken when using pooter
I guess ensuring that you don't suck the insects or specimen collected by ensuring there is a net in the pooter
How can the percentage of air be determined
Answer:
The composition of air can be determined by an experiment which includes passing a known volume of air, measured at a known temperature and pressure, over sufficient amount heated copper granules/powder, and measuring the volume gas remaining after the gas cools down to the temperature at which the first measurement was taken
Oxygen reacts with copper according to the following chemical reaction
2Cu (s) + O₂ (g) → 2CuO (s)
Cupper does not react with the other constituents of air
Whereby the initial volume of air was 100 cm³, we have;
Percentage of oxygen in air = 100 - The final volume reading of the container initially holding the air
When done using am appropriate experimental setup, the percentage of gases remaining equals 79% to 80%, therefore, the percentage composition of oxygen in air is between 20 and 21 percent
Explanation:
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Answer:
P¹V¹/T¹=P²V²/T² here
P²= 1.25- atm
V²=?
T²=345K
P¹=0.75-atm
V¹=120
T¹=295K
So V²= (0.75 x120/295)x(345/1.25)
Volume of the gas V²= 84.20- ml
Answer:
Solution given:
at first
volume[tex]V_{1}=120.0ml[/tex]
pressure [tex]P_{1}=0.75atm[/tex]
temperature [tex]T_{1}=22+273=295°K[/tex]
after increasing temperature and pressure
volume[tex]V_{2}=xml[/tex]
pressure [tex]P_{2}=1.25atm[/tex]
temperature [tex]T_{2}=70+273=343°K[/tex]
now
By using Combined gas equation[tex]\frac{P_{1}V_{1}}{T_{1}}=\frac{P_{2}V_{2}}{T_{2}}[/tex]
substituting value
[tex]\frac{0.75*120}{295}=\frac{1.25*x}{343}[/tex]
0.305=5x/1372
Doing criss cross multiplication
5x=0.305*1372
x=418.46/5
x=83.69ml
x=84ml
the volume will be 84ml
Do different color lights (RBG) use additive or subtractive properties to bring light of a certain color to our eyes?
Answer:
The lighting filters use subtractive properties to bring light of a color to the eye because subtractive color mixing uses white light source with a series of filter to eliminate certain wavelengths of light.
Different colour lights (RBG) uses additive properties to bring light of a certain color to our eyes.
What is color synthesis?Color synthesis is the art of forming different types of colours from small number of primary colours. The color formed is called a secondary color.
Color synthesis is carried out through the following means:
Additive color synthesis andSubtractive color synthesis.In additive color synthesis, the three primary colours lights that are combined is Red(R), Blue (B) and Green(G).
The wavelength from the various color light combine to generate white light which is visible to the eye.
Therefore, different colour lights (Red, Blue and Green) uses additive properties to bring light of a certain color(white) to our eyes.
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Consider the terms elements, compounds, and mixtures. What do you think each of
these is?
Answer:
Explanation:
Element -
It is the basic unit of matter, which cannot be broken down into substances by any way but can be combined to form new substances.
It is a pure substance.
It classifies into metals, non-metals, metalloids and noble gases.
Example - Hydrogen, Carbon, Oxygen
Compounds -
It is a combination of two or more elements.
It is a pure substance.
Through chemical reactions, they can be broken down into metals.
Example - Water, Carbon dioxide
Mixtures -
It is a combination of two or more elements or compounds or both.
The substances combined in a mixture are in a particular ratio.
Example - Chalk powder, Washing Soda
(True or false) Two or more atoms combine to form a molecule ____
Answer:
false tjytyjiy
Explanation:
cnruujrkyrryyrkkurk
Which is the best term to use when describing the energy of motion? chemical kinetic potential thermal
Answer:
Kinetic energy
Explanation:
Kinetic energy is the energy associated with an object's motion. It is mass and velocity dependent by a directly proportional relationship.
Potential energy is the energy associated with an object's position.
Thermal energy is the energy associated with heat addition or withdrawal.
Kinetic energy is the energy that a body possesses because of its movement, that is, it is the energy that arises when objects are in motion.
What is kinetic energy?It is that energy that a body or system possesses due to its movement.The amount of work done by all the forces acting on a body with a given mass, depends on the said mass and the speed of the body.Therefore, we can conclude that kinetic energy is the energy produced by its movements that depends on its mass and speed.
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Urgent please help
A.Ca
B. CaO
C.CO
In Rutherford experiment some alpha particles fired at a gold foil bounced backward as a result of ... A.reflection from the surfaces of gold atoms B.electrostatic repulsion by gold nuclei C.electrostatic repulsion by electronsD.all of the aboveE.none of the above
Answer:
B.electrostatic repulsion by gold nuclei
Explanation:
According to Rutherford's experiment, a thin gold foil was bombarded with alpha particles. Some of the particles passed through the foil undeviated, some were scattered through large angles while some bounced backwards.
It follows that the particles that bounced backwards must have encountered a massive particle of like charge.
The atom is composed of a nucleus which contains positively charged particles. Some of the alpha particles which are positively charged particles bounced back when they encountered the positively charged particles in the nucleus.
Answer: The correct option is B (electrostatic repulsion by gold nuclei).
Explanation:
In the Rutherford's experiment, he used positively charged particles called alpha particles to bombard an atom in order to find out what is inside the atom. Together with two other scientists, Geiger and Marsden, they used a narrow beam of alpha particles emitted from a radioactive source to bombard a thin gold foil. The scattering of the particles from the gold foil was detected by a movable zinc sulphide screen which could be rotated to various positions around the foil.
Each time an alpha particle hit the screen, a visible flash of light or scintillation was produced. This was observed by a microscope attached to the screen. It was then observed that some of the particles followed a straight path through the gold foil while a few where scattered in a backward direction. This was as a result of electrostatic repulsion by gold nuclei which occurs due to the greater part of the mass of the atom was concentrated in a minute nucleus with positive charge.
What is the correct equilibrium constant expression for the following reaction?
2NCl3(g) Û N2g) + 3Cl2g
Answer:
K = [N2] [Cl2]³ / [NCl3]²
Explanation:
The equilibrium expression, K, of a reaction:
aA + bB ⇄ cC + dD
Is defined as the ratio between the multiplication of concentrations of products powered to its reaction coefficient and the multiplication of concentrations of reactants powered to its reaction coefficient as follows:
K = [C]^c[D]^d / [A]^a[B]^b
Now, for the reaciton:
2NCl3 ⇄ N2(g) + 3Cl2(g)
K is:
K = [N2] [Cl2]³ / [NCl3]²
Which redox reaction would most likely occur if silver and zinc metal were
added to a solution that contained silver and zinc ions?
Click for a reduction potential chart
O A. Zn2+ + 2Ag → Zn + 2Agt
B. Zn2+ + 2Agt → Zn + 2Ag
C. Zn + 2Ag → Zn2+ + 2Ag+
D. Zn + Ag? → Zn2+ + 2Ag
Answer:
Zn²⁺ + 2Ag → Zn + 2Ag⁺
Explanation:
According to the reduction potential chart, silver ion (Ag⁺) is a stronger oxidizing agent than zinc (Zn), which is a reducing agent the compared to silver
Therefore, the redox reaction that will occur is that the zinc, Zn, will be oxidized to Zn²⁺ ion, while the silver, Ag²⁺ ion will be reduced to silver deposits Ag, therefore, the zinc will displace the silver in the solution containing silver and zinc ions because zinc is higher than silver in the reactivity series
The reduction potential Zn → Zn²⁺ + 2e⁻ = +0.76
The reduction potential for Ag⁺ + e⁻ → Ag = +0.8
Given that redox reactions are reversible, we get the following likely redux reaction:
Zn(s) + 2Ag⁺(aq) ⇄ 2Ag(s) + Zn²⁺(aq)
Zn²⁺(aq) + 2Ag(s) → Zn(s) + 2Ag⁺(aq) is the reaction most likely to occur.
****URGENT****
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the answers are there, i need someone to explain please!
Explanation:
your answer was correct
What is the principle of simple machine?
Convert the following absolute temperatures to centigrade.
i) 0 K
ii) 298 K
iii) 323 K
iv) 423 K
SHOW STEP BY STEP
Answer:
0 K
[tex]{ - \bf{273 \degree C}}[/tex]
298 K
[tex]{ \tt{ = 298 - 273}} \\ = { \bf{25 \degree C }}[/tex]
323 K
[tex]{ \tt{ = 323 - 273}} \\ = { \bf{50 \degree C}}[/tex]
423 K
[tex]{ \tt{ = 423 - 273}} \\ = { \bf{150 \degree C}}[/tex]
1.T=[£+273]
=273
It is because kelvin temperature is absolute zero.
1.One gram-atom of Nitrogen is heavier than one gram-atom of Oxygen.
True or false
2.Measurements of a physical quantity. can be very precise but not accurate
True or False
Answer:
1 . statement is false
2. statement is true
What do Van der Waals forces do?
Answer:
they are weak forces that attract neutral molecules to one another
Explanation:
particles in liquid or air vibrate and move constantly thus they collide
15. How many moles of CaCl are in 250. mL of 3.00 M of CaCl solution?
a. 750. mol
b. 1.33 mol
C. 83.3 mol
d. 0.750 mol
e. 3.00 mol
Describe how a constant volume calorimeter can be used to measure the heat transferred from a burning piece of coal to cool water.
thank you <3
Answer:
A Calorimeter is a device used to measure the amount of heat involved in a chemical or physical process.
Explanation:
Ex- when an exothermic reaction ( accompanied by or requiring absorption of heat)occurs in solution in a calorimeter, the heat produced by the reaction is absorbed by the solution increasing its temperature.
- When an endothermic reaction (Heat evolving reaction) occurs, the heat required is absorbed from the thermal energy of the solution, decreasing its temperature.
A burning piece of coal which is releasing heat due to its combustion and is transferred to water.
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the solubility of sugar is 250 at 60° what does it mean. please helpp anyone please help
I don't know I am having the same problem
PLZ HELP what is a sign that a chemical change has happened
Answer:
Some signs of a chemical change are a change in color and the formation of bubbles. The five conditions of chemical change: color change, formation of a precipitate, formation of a gas, odor change, temperature change.
describe the process to electroplating with the help of an activity
Answer:
process of depositing a thin layer of any superior metal over an object of a cheaper metal, with the help of electric current
Explanation:
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what is bonding in chemistry
Explanation:
A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the electrostatic force of attraction between oppositely charged ions as in ionic bonds or through the sharing of electrons as in covalent bonds.
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Answer:
Check Down
Explanation:
A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the electrostatic force of attraction between oppositely charged ions as in ionic bonds or through the sharing of electrons as in covalent bond.
Nal+ pb(SO4) 2 Pbl4 + Na2SO4 explain how to balance the chemical equation and classify its reaction type
Explanation:
because there are 4 Iodines on the left, we'll put. 4 in front of NaI to balance it. This would result in 4 Na on the left, so we'll put a 2 in front of Sodium Sulfate to balance the right side. Now we have 4 Na and I on both side, as well as 2 Sulfate on both sides. Pb is already balanced. The equation is now complete.
is zinc a basic radical or acid radical?
Answer:
depends on the element it's reacting with..
Explanation:
if the another element requires less energy to loose electron then zinc will become negatively charged and hence becomes acidic radical..
normally if it is reacting with element with valency 4 and Atomic number less than it(Ti,Si,C) then it will lose electron and gain positive sign and henve becomes basic radical..
If a pile of a deson of Buttons has a height of 2cm 4mm, what is the thickness of one to button.
The thickness of one button will be 2mm
According to this question, a pile of a dozen buttons has a height of 2cm 4mm. A dozen means 12, hence, 12 buttons has a height of 2cm 4mm.* N.B: We convert the height of the 12 buttons to same unit (mm)
Since 1cm = 10mmThen, 2cm = 2 × 10 = 20mm
20mm + 4mm = 24mm
That is, twelve buttons (a dozen) has a thickness of 24mm, one button will therefore, be:24/12 = 2mm thick
Hence, one button is 2mm thick.
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