Instant hot and cold packs are found in many common stores and work when two substances react. Depending on the substances that react, the reaction either absorbs heat or gives off heat. The enthalpy of a hot pack is negative because the reaction gives off heat. If The enthalpy of a hot pack is positive because the reaction absorbs heat.
Define enthalpy?A thermodynamic system's internal energy and the product of its pressure and volume are added to form enthalpy, which is one of the system's properties. It is a state function that is frequently used to monitor chemical, biological, and physical systems at a constant pressure that is conveniently given by the sizable surrounding environment.In a thermodynamic system with constant pressure, the total amount of heat is measured in terms of enthalpy. It is shown to be. H is equal to E + P + V, where E denotes internal energy, P denotes pressure, and E denotes energy. In a thermodynamic system, entropy represents the degree of chaos.The measurement of energy in a thermodynamic system is called enthalpy.To learn more about enthalpy refer to:
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PLS HELP ME THIS IS DUE TODAY BRO ILL BRAINLIST U JUST DO THE ONES U KNOW WAJDHWNDIGB!
Answer: Helium: atomic number 2. EC 2
Neon: atomic number 10. EC 2,8
hydrogen: atomic number 1. EC 1
magnesium: atomic number 12. EC 2,8,2
chlorine: atomic number 17. EC 2,8,7
Aluminum: atomic number 13. EC 2,8,3
Explanation: hope this helped
When talking about the products of photosynthesis, why is it a HUGE issue when a vast amount of the rainforests is dying along with vast acres of forests from fires/deforestation? Remember, we know that this hurts the ecosystems of animals living there, but what else does it effect? Question 5 options: the creation of too much water the creation of oxygen the creation of to much heat the creation of carbon monoxide
Answer:d
Explanation:because im really really sure thats the answer
iron (ii) hydroxide + sodium nitrate. Name the precipitate formed in reaction
In the formula XS04, the symbol X could represent the element*
O (1) AI
O (2) Ar
O (3) Mg
0 (4) Na
the empirical formula is C6H6O.vapour density is 47.find the molecular formula
Answer: The molecular formula will be [tex]C_6H_6O[/tex]
Explanation:
Molecular formula is the chemical formula which depicts the actual number of atoms of each element present in the compound.
Empirical formula is the simplest chemical formula which depicts the whole number of atoms of each element present in the compound.
The empirical formula is [tex]C_6H_6O[/tex]
The empirical weight of [tex]C_6H_6O[/tex] = 6(12)+6(1)+1(16) = 94 g.
The molecular weight = [tex]2\times \text{vapour density}=2\times 47=94[/tex]
Now we have to calculate the molecular formula.
[tex]n=\frac{\text{Molecular weight}}{\text{Equivalent weight}}=\frac{94}{94}=1[/tex]
The molecular formula will be=[tex]1\times C_6H_6O=C_6H_6O[/tex]
Is barium hydroxide Ba(OH)2 or is BaOH?
Answer:
What is the charge on the barium ion and what is the charge of the hydroxide ion.
Explanation:
To get the correct formula they have to add to zero over all.
How much heat is absorbed in the complete reaction of 3.00 grams of SiO2 with excess carbon in the reaction SiO2(g) + 3C(s) → SiC(s) + 2CO(g) ΔH° = 624.7 kJ/mol?
Answer:
31.24 kJ
Explanation:
SiO₂(g) + 3C(s) → SiC(s) + 2CO(g) ΔH° = 624.7 kJ/molFirst we convert 3.00 grams of SiO₂ to moles, using its molar mass:
3.00 g SiO₂ ÷ 60.08 g/mol = 0.05 molNow we calculate the heat absorbed, using the given ΔH°:
If the complete reaction of 1 mol of SiO₂ absorbs 624.7 kJ, then with 0.05 mol:
0.05 mol * 624.7 kJ/mol = 31.24 kJ of heat would be absorbed.The heat absorbed by 3.00 grams of SiO2 is 31.17 kJ/mol.
The thermochemical equation is;
SiO2(g) + 3C(s) → SiC(s) + 2CO(g) ΔH° = 624.7 kJ/mol
The number of moles of SiO2 = 3.00 g/60.08 g/mol = 0.0499 moles
From the reaction equation;
1 mole of SiO2 absorbs 624.7 kJ/mol
0.0499 moles SiO2 absorbs 0.0499 moles × 624.7 kJ/mol/1 mole
= 31.17 kJ/mol
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he distance from Earth to the North Star is about 430 light-years. Which of the following statements describes why scientists use the light-year unit to measure distances in space?
A light-year unit is very small and distances in space are very small.
A light-year unit is very small and distances in space are very large.
A light-year unit is very large and distances in space are very small.
A light-year unit is very large and distances in space are very large.
Answer:
D
Explanation:
because the rest don’t make any sense
A light-year unit is very large and distances in space are very large. Therefore, the correct option is option D.
What is distance?No matter the direction of the journey, distance is the overall path that an item in motion has traveled. Since just the length of the path travelled is calculated as well as the motion's direction is ignored, distance is referred to as a scalar number. The distance can only ever be positive; it can never be 0 or negative.
Displacement generally defined as the overall alteration of an object's location and motion direction. Displacement is recognized as a vector quantity since it takes into consideration both the directions of the motion and the amount of the changing position. Displacement may be zero, positive, or negative. A light-year unit is very large and distances in space are very large.
Therefore, the correct option is option D.
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Which of the following examples is a chemical property?
Answer:
Examples of chemical properties include flammability, toxicity, acidity, reactivity (many types), and heat of combustion. Iron, for example, combines with oxygen in the presence of water to form rust; chromium does not oxidize (Figure 2).
Explanation:
Select the correct answer.
When a substance changes from one phase to another, which of the following occurs?
OA. The substance loses or gains heat.
shoes
OB. The average kinetic energy of the substance changes.
OC. The temperature of the substance changes.
OD. The molecular motion of the substance changes.
Reset
Next
D. The molecular motion of the substance changes.
At sea level, a kilogram welghs approximately
2 pounds
10 pounds
5 pounds
1 pound
Answer:
1 kilogram weight at sea level would be the equivalent of 2 pounds.
Explanation:
hey guys i dont want to beg for help but i just am stuck in this q please help
I try this before but for me is letter C
Answer:
C
Explanation:
i took the test
Does anybody know how to find the theoretical yield? you can just do 1 equation
Answer:
its the first part in mass of sodium
Explanation:
:)
Now molecules: Choose... molecules of H 2 + Choose... molecules of O 2 → Choose... molecules of H 2 O
Answer:
2 H2 + 1 O2 → 2 H2O
Explanation:
Which group (family) of non-metals does not form ions?
Answer:
Noble gasses
Explanation:
nobled gasses
all elements want to loose or gain electrons to be like the noble gasses in bonding but the noble gasses do not bond.
Do you think personality
traits are primarily inherited
from your parents or
influenced by the
environment? What is your
evidence you researched?
Personality traits are influenced by a combination of genetic and environmental factors. Research suggests that both genetics and the environment play significant roles in shaping an individual's personality.
Studies on twins and adoption give proof that genetics affect personality. When opposed to fraternal twins, who only share 50% of their genetic makeup, identical twins, who share 100% of their genetic material, frequently show stronger similarities in personality traits. This shows that certain personality traits are influenced by hereditary factors.
Yet, environmental influences also have a considerable impact on personality. Despite having comparable DNA, studies on non-twin siblings reared in the same home have found that they frequently display personality differences.
This shows that the environment, including parental practices, cultural influences, and life events, has a significant impact on personality development.
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Explain why the metals conduct electricity
write in your own words please, don't copy-paste from internet
Answer:
Metals conduct electricity because the electrons inside the metal are relatively free to move. So when electricity is pass through metals, electrons carry electricity and spread it all over the metal. The mobility of electrons is the reason why metals conduct electricity.
4 points
What is the volume of an object with a density of 5.20 g/cm3 and a mass
of 6.00 x 10^2? g?
9. This type of bond consists of closely packed cations and loosely held valence e- rather than
neutral atoms.
a. lonic
b. Covalent
c. Metallic
d. polyatomic
Determina la densidad de una barra dd hierro cuya masa ed de 160gr y su volumen es de 20,35cm³ ¿que volumen ocuparan 12g de hierro?
Answer:
15.26 cm³
Explanation:
La densidad de una sustancia se define como su masa por unidad de volumen:
densidad = masa/volumen
Tenemos los siguientes datos de la barra de hierro:
masa = 160 g
volumen = 20,35 cm³
Por lo tanto, la densidad de la barra de hierro es:
densidad = 160 g/20,35 cm³ = 0.786 g/cm³
El volumen de 12 gramos de hierro se calcula utilizando el dato de masa (12 g) y la densidad calculada:
densidad = masa/volumen ⇒ volumen = masa/densidad
= 12 g/(0.786 g/cm³)
= 15.26 cm³
The purpose of mitosis is to produce
A. Sex cells
B. Body cells
C. DNA
can someone please explain this i will give brainliest
All elements in this series are radioactive
Answer:
you did not posted the series
Explanation:
Why doesn't the Earth usually feel solar winds?
A. because of the aurora borealis
B. because of its strong magnetic field
C. because of strong magnetic activity inside the Sun
D. because they contain electromagnetic radiation
C6H12O6 O3 NF3 Co KNO3 H2 CO
Which one of these are molecules list all that apply
You're leaving a carnival and you're pumped because a clown just handed you a red, helium- filled balloon. But then, something tragic occurs. You hear the ice cream truck, jump with joy doing a 180 degrees in the air, and you lose grip of your beautiful balloon. Upward it flies as you stare speechless into the sky. Why did this helium balloon fly away instead of falling to the ground like a balloon filled with your breath usually does?
Question 4 of 20
A student is performing experiments on a particular substance. Which
statement is an observation of a chemical property of the substance?
A. Its viscosity decreases.
B. It boils.
C. Electricity passes through it.
D. It reacts with acid.
SUBMIT
Answer:
D
Explanation:
Reacting with acid is the only chemical property out of the 4 options. The rest are physical
If sodium (Na) bonds with chlorine (Cl), which statement is true?
An electron is transferred from sodium to chlorine and an ionic bond is
formed.
An electron is shared between sodium and chlorine and an ionic bond is
formed.
An electron is transferred from sodium to chlorine and a covalent bond is
formed.
An electron is shared between sodium and chlorine and a covalent bond is
formed.
Answer:
First Statement is correct
Explanation:
An electron is transferred from sodium to chlorine and ionic bond is formed.
Hope it help!!
If sodium ( Na ) bonds with chlorine ( Cl ), then an electron is transferred from sodium to chlorine and an ionic bond is formed. Therefore, option A is correct.
What is ionic bond ?The main interaction taking place in ionic compounds is ionic bonding, a form of chemical bonding that includes the electrostatic attraction between two atoms or ions with dramatically differing electronegativities.
When the ionic character is larger than the covalent character, i.e., when there is a significant difference in the electronegativity between the two atoms, the bond is more polar than when the electrons are divided more evenly in covalent bonding.
The ionic bond found in the salt sodium chloride is an illustration of this type of connection. The valence electron from sodium is transported to chloride's outer electron shell.
Thus, option A is correct.
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how many moles of water are required to produce 2.15 mol oxygen gas in this reaction
What is the momentum of a car with a mass of 1,300 kg traveling north at a speed of 28 m/s?
Answer:
p = 36400 kg·m/s
Explanation:
p=mv
p= Momentum
m= mass (1300 kg)
v= 28
1300 × 28
= 36400 kg·m/s
The Momentum of the car is 36400 kg-m/s.
What is Momentum ?Momentum is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. m is an object's mass and v is its velocity
Given that,
Mass of the car, m = 1300 kgSpeed of the car, v = 28 m/s (towards north)(m is an object's mass and v is its velocity)
To find :
The momentum of car, p
Solve :
Let p is the momentum of an object. It can be calculated by the product of mass and its velocity. The formula to find it is given by :
p = m x v
= 1300 x 28
= 36400 kg-m/s.
Therefore, the momentum of the car is 36400 kg-m/s.
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