The calorific capacity of a substance related to the temperature when specific heat of a substance ∆Q changes.
What is specific heat?Specific heat is defined as the heat required to raise the temperature of 1 gram of a substance by one degree.
Specific heat = q/(∆T × mass of the substance)
What is Heat capacity?Heat Capacity is defined as the amount of heat required to raise the temperature of the system by one degree.
Units of heat capacity :
The unit of heat capacity are joule/kelvin or joule/Celsius.
Heat capacity at constant volume = dU/dTHeat capacity at constant pressure = dH/dTThus, we concluded that the calorific capacity of a substance related to the temperature when specific heat of a substance ∆Q changes.
learn more about heat capacity:
https://brainly.com/question/13411214
#SPJ13
Copper metal has a density of 8.96 G/cm^3. What volume (in cm) does a 26.0 g piece of Cu occupy?
The volume (in cm) does a 26.0 g piece of Cu is 2.90 cm³.
Density is the substance's mass in keeping with a unit of volume. The image most often used for density is ρ, despite the fact that the Latin letter D also can be used. Mathematically, density is defined as mass divided by volume.
Mass, extent, and density are three of an object's maximum simple residences. Mass is how heavy something is, quantity tells you how big it is, and density is mass divided through volume. although mass and extent are houses you deal with each day, the concept of density is a little much less obvious and takes a cautious idea.
The components for density are the mass of an object divided by means of its volume. In equation shape, it is d = m/v, in which d is the density, m is the mass and v is the volume of the object. the standard devices are kg/m³.
Density = mass / volume
Volume = mass/density
= 26/8.96
= 2.90 cm³
Learn more about density here:-https://brainly.com/question/1354972
#SPJ1
Wine goes bad soon after opening because the ethanol CH3CH2OH in it reacts with oxygen gas O2 from the air to form water H2O and acetic acid CH3COOH, the main ingredient of vinegar.
What mass of water is produced by the reaction of 6.5g of ethanol?
Round your answer to 2 significant digits.
The mass of water produced in the oxidation reaction is 2.5 g.
What is oxidation reaction of ethanol?
Oxidation reaction of ethanol occurs when ethanol comes in contact with oxygen, producing water and acetic acid. This type of reaction can also produce carbon dioxide and water.
The oxidation reaction of ethanol and oxygen is given as;
CH₃CH₂OH + O₂ -----------> H₂O + CH₃COOH
Molecular mass of ethanol;
CH₃CH₂OH = (12) + (3 x 1) + (12) + (2 x 1) + (16) + (1) = 46 g/mol
Molecular mass of water;
H₂O = (2 x 1) + (16) = 18 g/mol
From the reaction above, we can infer the following;
46 g of ethanol ---------> 18 g of water
6.5 g of ethanol ---------?
= (6.5 x 18) / 46
= 2.54 g of water
Thus, the mass of water that is produced by the reaction of 6.5g of ethanol is 2.5 g.
Learn more about oxidation reaction here: https://brainly.com/question/27239694
#SPJ1
Seawater contains roughly 28.0 g of NaCl per liter. How many moles of NaCl is in each liter of seawater?
Answer:
About 0.479 moles
Explanation:
Balance the equation KO2(s)+CO2(g)→K2CO3(s)+O2(g)
The balanced equation is
4 KO2(s) + 2 CO2(g) = 2 K2CO3(s) + 3 O2(g).
What is the are balanced equation?The law of conservation of mass states that the mass of the reactants and products of a chemical reaction should be equal. The amount of atoms for each element doesn't really increase as a consequence of the chemical reaction. Thus, the chemical equation illustrating the chemical process must be balanced. A chemical equation is said to be balanced when the number of atoms involved on the reactants and products sides are equal.
Here are the steps we need to do in order to balance an equation:
Each element's atoms in the reactants and products should be counted.Use coefficients and add them before the compounds as necessaryTo know more about balanced equation , visit:
https://brainly.com/question/28777563
#SPJ9
Practice
5. The Republic of China presented one of the world's largest flags to the city of
Kaohsiung in 1989. The flag of the Republic of China measured 1.26 × 10^4 cm
by 8.40 x 10³ cm. What is the area of this flag in square centimeters?
The area of this flag in square centimeters is 10.58 × [tex]10^{7} cm^{2}[/tex].
What is the area of a rectangle?The quantity of unit squares that fit inside a shape determines its area. A unit square is a square having a side of one unit, as "unit" here denotes one (1). The total number of unit squares that are contained within a rectangle's perimeter is hence its area. Or, you can refer to the area of the rectangle as the region included within the rectangle's envelope. The rectangular tiles that make up your home are a fantastic illustration of form. The number of tiles on the floor makes it simple to calculate how much area it takes up. You may calculate the rectangle's area using this as well. A number of unit squares equal the area of a rectangle.
Area of flag = area of a rectangle
= l × b
= 1.26 × [tex]10^{4}[/tex] × 8.40 ×[tex]10^{3}[/tex]
= 10.58 × [tex]10^{7}[/tex] [tex]cm^{2}[/tex]
To know more about the area of a rectangle, visit:
https://brainly.com/question/2607596
#SPJ9
how many molecules O2 has in 32 oxygen?
Answer:
One mole of oxygen gas, which has the formula O2, has a mass of 32 g and contains 6.02 X 1023 molecules of oxygen but 12.04 X 1023 (2 X 6.02 X 1023) atoms, because each molecule of oxygen contains two oxygen atoms.
How many moles of N are in 0.179 g of N₂O?
0.008134 moles of N are in 0.179 g of N₂O.
1mole = 6.022 ×1023 number of moles of atoms or molecules or ions
Number of moles = Mass /molar mass
Number of moles of N2O = 0.179g/44.014g/mol = 0.004067mol
one mole of N2O contains two moles of N
Number of moles of N = 2× 0.004067 = 0.008134 moles.
What is mole fraction ?
The mole fraction can be calculated by dividing the number of moles of one factor in the reaction by the total number of moles of all impurities in the solution. It should be noted that the sum of the mole fractions of all components of the solution must be equal to one.
A mole fraction is a unit of attention. the relative amount of solute and solvent in the reaction is measured as a mole fraction and reported. Mole fraction is the wide range of moles of a given substance in solution divided by the total range of moles.
To learn more about mole fraction, visit;
https://brainly.com/question/28196871
#SPJ13
Compare the behavior of the mixture of gases with each solitary gas in the presence of flame.
The heat made by a mixture of gases is less than that produced by solitary gases of hydrogen or oxygen.
How are the gases behave in the mixture?The property becomes a solution of a homogeneous mixture. Some of the effects of gas mixtures are easy to control. if we know the composition of the gases in the mix. In gas mixtures, all components in the gas phase can be used separately. The atmosphere is a mixture of different gases. The part, usually present in solution, first has to be atomized in a flame. Premixed combustion flame, a mixture of fuel and oxidant gas, and diffusion. compared to liquid streams, is relatively simple because the bulk characterization of a single phase is implicit. However, when gas. The heat produced by a mixture of gases is less than that produced by solitary gases. of hydrogen or oxygen.
so we can conclude that the flame appears yellow if there are impurities in the air whereas a pure hydrogen gas flame will not produce any smoke.
Learn more about gases here: https://brainly.com/question/25736513
#SPJ1
How much heat does it take to raise the
temperature of 225 g of water from 25.0°C to 100.0°C?
Answer:
7.06 x 10⁴ J
Explanation:
To find the amount of heat necessary to heat the water, you need to use the following equation:
Q = mcΔT
In this equation,
-----> Q = heat (J)
-----> m = mass (g)
-----> c = specific heat capacity (J/g°C)
-----> ΔT = change in temperature
The specific heat capacity of water is 4.186 J/g°C. You can plug the given values into the equation and simplify to find "Q".
Q = ? J c = 4.186 J/g°C
m = 225 g ΔT = 100.0°C - 25.0°C = 75.0°C
Q = mcΔT <----- Given equation
Q = (225 g)(4.186 J/g°C)(75.0°C) <----- Insert values
Q = 7.06 x 10⁴ J <----- Multiply
If 150 grams of N2H4 and 200 grams of N2O4 are mixed what is the limiting reactant
Answer: N2O4
Explanation:
N2H4 molecular weight is 32 150g/32 = 4.7 mol
N2O4 Molecular weight is 92 200/92 = 2.2 mol
So the N2O4 has less moles present and will be the limiting reactant.
5. What is the volume of 10 moles of a gas at 300 K held at a pressure of 3.5 atm?
70.33 L is the volume of 10 moles of a gas at 300 K held at a pressure of 3.5 atm.
What is volume?Volume is the percentage of a liquid, solid, or gas's three-dimensional space that it occupies.
Liters, cubic metres, gallons, millilitres, teaspoons, and ounces are some of the more popular units used to express volume, though there are many others.
We will use ideal gas law to find the volume
PV = nRT
Can also be written as
V = (nRT)/P
Where,
P = pressure
V = volume
n = amount of substance
R = ideal gas constant
T = temperature
Here, we have given
P = 3.5 atm
V = to find
n = 10 moles
R = 0.08206 L⋅atm/K⋅mol
T = 300k
Lets substitute the values
V = (10 × 0.08206 × 300)/3.5
V = 70.33 L
Learn more about volume
https://brainly.com/question/463363
#SPJ10
A titration procedure between H2SO4 and LiOH required a volume of 15.50 ml of 0.1000 M LIOH solution to reach the end point. If this titration utilized 20.00 ml. of H2SO4
what is the molarity of this H2SO4 solution?
Express your answer using four sig figs
The molarity of the 20 mL H₂SO₄ solution required for the titration is 0.0388 M
How do I determine the molarity of H₂SO₄We can obtain the molarity of the H₂SO₄ solution by doing the following:
H₂SO₄ + 2LiOH —> Li₂SO₄ + 2H₂O
The mole ratio of the acid and base obtained from the equation is:
The mole ratio of the acid, H₂SO₄ (nA) = 1The mole ratio of the base, LiOH (nB) = 2From the question given, we obtained the following:
Volume of base, LiOH (Vb) = 15.50 mLMolarity of base, LiOH (Mb) = 0.1000 MVolume of acid, H₂SO₄ (Va) = 20 mLMolarity of acid, H₂SO₄ (Ma) =?MaVa / MbVb = nA / nB
(Ma × 20) / (0.1 × 15.5) = 1 / 2
(Ma × 20) / 1.55 = 1 / 2
Cross multiply
Ma × 20 × 2 = 1.55
Ma × 40 = 1.55
Divide both side by 40
Ma = 1.55 / 40
Ma = 0.0388 M
Learn more about titration:
https://brainly.com/question/28041246
#SPJ1
Interpret the following equation for a chemical reaction using the coefficients given: N2(g) + 2 O2 (g) = 2 NO2 (g)
Interpretation of equation for a chemical reaction using the coefficients
On the particulate level: 1 molecule of N₂(g) reacts with 1 molecule of 2O₂(g) to form 2 molecules of NO₂(g).
On the molar level: 1 mole of N₂(g) reacts with 1 mole of 2O₂(g) to form 2 moles of NO₂(g).
What is a chemical reaction?chemical reaction: a process in which one or more substances—the reactants—are changed into one or more additional substances—the products. Chemical elements and compounds are both substances. To produce different substances as products, a chemical reaction rearranges the atoms that make up the reactants. Technology, culture, and life itself are all influenced by chemical reactions.
Numerous activities that involve chemical reactions have been known and used for thousands of years, including burning fuels, smelting iron, creating glass and pottery, brewing beer, and producing wine and cheese.
Numerous intricate processes that take place in all living systems, as well as the Earth's geology, atmosphere, and oceans, involve chemical reactions.
We have given the following chemical reactions
N₂(g) + 2O₂(g) → 2NO₂(g)
The changes in two levels, the particulate level and the molar level, can be interpret using the balanced equation.
On the particulate level, we always consider discrete molecules.
On the particulate level: 1 molecule of N₂(g) reacts with 1 molecule of 2O₂(g) to form 2 molecules of NO₂(g).
We think in terms of moles On the molar level, considering 1 mole of particles = 6.02 × 10²³ particles.
On the molar level: 1 mole of N₂(g) reacts with 1 mole of 2O₂(g) to form 2 moles of NO₂(g).
Learn more about Chemical reactions
https://brainly.com/question/14120101
#SPJ9
Classify each compound/molecule based on its ability to form a "Strong Electrolyte", "Weak Electrolyte", or "Nonelectrolyte" aqueous solution.
© (NH)2CO (Urea)
Urea is a nonelectrolyte.
What is a nonelectrolyte?A material that conducts electricity poorly and does not easily ionize when dissolved or melted.
Chemical substances that don't conduct electricity in any condition are called non-electrolytes. As a result, current does not flow through the solution since it does not add ions to it. Naphthalene, latex, and sugar solution are a few examples of covalent compounds that are not electrolytes. An object is an electrolyte if it is electrically conductive when it is liquid or dissolved. It is a nonelectrolyte if it does not conduct electricity while it is a liquid. In an aqueous solution, nonelectrolytes—such as sugar, alcohol, and many organic compounds—occur as uncharged molecules and do not conduct electrical current.
To know more about nonelectrolyte ,visit:
https://brainly.com/question/15079452
#SPJ9
A mineral is dropped into a weak acid and bubbles form.
What type of property does this demonstrate?
A 8.54 g solid sample of sodium hydroxide is dissolved in 111.5 g of water in a coffee cup calorimeter. By how many degrees will the temperature of the solution rise? The heat of solution for solid sodium hydroxide is 44.5 kJ/mol.
Based on the heat of solution, the increase in temperature rise when an 8.54 g solid sample of sodium hydroxide is dissolved in 111.5 g of water in a coffee cup calorimeter is 95.48 K.
What is the temperature rise when an 8.54 g solid sample of sodium hydroxide is dissolved in 111.5 g of water in a coffee cup calorimeter?The increase in temperature rise when an 8.54 g solid sample of sodium hydroxide is dissolved in 111.5 g of water in a coffee cup calorimeter is determined using the formula below:
ΔH = m * c * ΔTmass of water = 111.5 g
c = 4.18 J/g.K
Heat of solution, ΔH = 44.5 kJ/mol
ΔT = ?
Mole of NaOH in 8.54 g NaOH = 8.54/40
Mole of NaOH in 8.54 g NaOH= 0.2135 mol of NaOH
Solving for ΔT;
44.5 kJ/mol = 111.5 * 4.18 * ΔT
44.5 kJ/mol = 466.07 * ΔT
ΔT = 44.5 / 466.07
ΔT = 95.48 K
Learn more about heat of solution at: https://brainly.com/question/28169738
#SPJ1
• When dissolved 1.93 g of HNO₂ acid (M.W = 47) and dilute
the volume to 500 ml the H concentration in the solution was
7.63X10³ M, calculate the dissociation constant of K
a?
The dissociation constant of Ka is 7.83 × 10³ .
What does molar mass mean?In chemistry, the molar mass of a chemical compound is determined by dividing its mass by the quantity of the material, or the number of moles in the sample, expressed in moles. A substance's molar mass is a bulk attribute, not a molecular one. Mass per mole is one way to define molar mass. Molar mass is, in other words, the total mass of all the atoms in a substance that makes up a mole. It is quantified in grams per mole.
Molar mass is shown for substances or molecules. The molar mass of a single element or atom would simply be that element's mass represented in atomic mass units.
Mass of HN[tex]O_{2}[/tex] = 1.93g
Volume of solution = 500 ml
[tex]H^{+}[/tex] equilibrium = 7.63 × [tex]10^{3}[/tex] m
Molarity of HN[tex]O_{2}[/tex] = mol [tex]HNO_{2}[/tex] /vol in2
mol [tex]HNO_{2}[/tex]
= mass(g) / molar mass
= 1.93/42.0129 g/mol
= 0.04105
Hence ,
molarity of HNO2
= 0.04105/0.5L
= 0.0821 M
Reaction
HNO2 ⇄ H+ NO2
x = [tex]H^{+[/tex] = 7.63 × [tex]10^{3}[/tex] M
= 0.0821 - 7.63 [tex]10^{3}[/tex]
= 0.0821 - 0.00763
= 0.0745 m
[tex]H^{+}[/tex] = 7.63 × [tex]10^{3}[/tex]
[tex]NO_{2}[/tex] = x = 7.63 × [tex]10^{}[/tex]³
Dissociation of constant ka
ka = [tex]H ^{+} NO_{2} ^{-}[/tex]/ HNO²
=[tex]10^{3}[/tex] × 7.83
To know more about molar mass , visit:
https://brainly.com/question/20552052
#SPJ9
a jar of crunchy butter contain 1.26 kg of peanut butter . if you use 7.7% of the peanut butter for a sandwich how many ounces of peanut butter did you take out of the container
The mass of the peanut butter that you took out of the container is 34.1 ounces
What is a conversion factor?The conversion factor is the manner in which we are able to change a value from one unit to another, Let us recall that there could be several units that could be used for a particular calculation and many times it is necessary to convert a value from one of the units to another for ease of calculation.
Mass of the crunchy butter = 1.26 kg
Percent used = 7.7%
Mass of the crunchy butter used = 7.7/100 * 1.26 kg = 0.97 Kg
To convert to ounces;
0.97 Kg * 35.247 ounces/1 Kg
= 34.1 ounces
Learn more about conversion factor:https://brainly.com/question/28366871
#SPJ1
) Describe five mechanisms that promote aggregation in soils.
Answer:
wetting and drying
cultivation
freezing and thawing
particle size
Earthworm
what us a bond between a positive and a negative ion called
Answer: ionic bond
Explanation:
I need help with this!
Answer:
1. Fe: 26, 26, 30
2. Rh: 45, 45, 58
3. Sr: 38, 38, 50
4. Li: 3, 3, 4
5. Bi: 83, 83, 126
Explanation:
Protons = electrons = atomic number
Atomic mass - atomic number = neutron
Calculate how many grams of Fe2O3 (molar mass 159.70 g/mol) are formed when 16.7 g of Fr react completely with O2.4 Fe + 3 O2—> 2 Fe2O3
The first step to solve this question is to convert the given amount of grams of Fe to moles using its molecular weight.
[tex]16.7gFe\cdot\frac{mol}{55.845gFe}=0.3molFe[/tex]According to the given reaction, 4 moles of Fe produce 2 moles of Fe2O3. Use this ratio to find how many moles of Fe2O3 are formed:
[tex]0.3molFe\cdot\frac{2molFe_2O_3}{4molFe}=0.15molFe_2O_3[/tex]Convert this amount of moles to grams using Fe2O3 molar mass:
[tex]0.15molFe_2O_3\cdot\frac{159.70g}{molFe_2O_3}=23.9g[/tex]It means that 23.9 grams of Fe2O3 are formed.
How will you apply the concept of biology,chemistry, and homeostasis in your future career
My ability to interconnect my understanding in biology, chemistry and homeostasis makes me a great scientist as I will apply all these in my future career by:
Making sure I feed on a healthy balance diet.Separating mixtures of insoluble solids from solutions by way of filtration.Recognizing my response to certain dangerous situation when the emergency hormones are released.What is meant by an emergency hormones?These are the hormones which are released when we suddenly find ourselves in a dangerous or life threatening situation such as we need manage risk or prevent accident. This hormone is known as adrenaline. They are known as flight or fight hormones.
So therefore, the knowledge I acquired from biology, chemistry and homeostasis will used to make my career more productive in the nearest future.
Read more on career:
https://brainly.com/question/6947486
#SPJ1
What quantity in moles of phosphorus atoms do you have if you have 2.40 × 10²² atoms of phosphorus. (The mass of one mole of phosphorus is 30.97 g.)
Answer:
0.04 mole or 1.23 g
Explanation:
1 mole of P has 6.02 x 10^23 atoms
so quantity in moles of P of 2.40 x 10^22 atoms equal
1 mole x (2.40 x 10^22)/(6.02 x 10^23)
= 0.03986710963 or 0.04 mole
1 mole of P = 6.02 x 10^23 atoms = 30.97 g
2.40 x 10^22 atoms weights
(30.97)(2.40 x 10^22)/(6.02 x 10^23)
= 1.23468438538 or 1.23 g
A student placed a sample of a food coloring that contains a mixture of a blue dye and a red dye at the top of a chromatography column filled with a nonpolar stationary phase. When water is poured through the column, two bands of colors are seen in the column, as shown in the diagram above.
A student collects a sample of the blue dye from the column in a cuvette. Which of the following is least useful to determine the concentration of the sample using a spectrophotometer set at 640nm?
A. The volume of a sample
B. The path length of the cuvette
C. The absorbance of the dye at 640nm
D. The solar absorptivity of the dye at 640nm
Based on the principles of spectrophotometry, the least useful to determine the concentration of the sample using a spectrophotometer set at 640nm is: the volume of a sample; option A.
What is spectrophotometry?Spectrophotometry is an analytical technique that is used to measure the concentration of a solution by measuring how much light the solution absorbs or transmits when a beam of light of a given wavelength is passed through it.
In spectrophotometry, the concentration of a solution is directly proportional to its absorptivity. This implies that the higher the concentration of a solution, the higher the amount of light absorbed by the solution.
The absorptivity of the solution is inversely proportional to the transmissivity of the solution.
The higher the concentration, the lesser the amount of light the solution will transmit.
The factors that are important in calculating the concentration of a solution are:
The path length of the cuvetteThe absorbance of the dye at a given wavelengthThe solar absorptivity of the dye at a given wavelengthLearn more about spectrophotometry at: https://brainly.com/question/14854785
#SPJ1
Which of the following statements concerning quantum mechanics is/are true?
1. The behavior of submicroscopic particles can sometimes be described as waves.
2. Quantum mechanics limits us to making statistical statements about the location of an electron in an atom.
3. The uncertainty principle is important only for particles of very small mass, such as the electron.
1. The behavior of submicroscopic particles can sometimes be described as waves - True
2. Quantum mechanics limits us to making statistical statements about the location of an electron in an atom - True
3. The uncertainty principle is important only for particles of very small mass, such as the electron - True
What is quantum mechanics?Quantum mechanics is the branch of science that deals with the particles that we have in the atom. The study of quantum mechanics led us to appreciate the position of the electrons that are found in the atom.
The spear head of the study of quantum approach to the atom was Erwin Schrodinger when he proposed the wave mechanical model of the atom.
Learn more about quantum mechanics;https://brainly.com/question/11855107
#SPJ1
When the solid and liquid phases of a substance are present. simultaneously, which phase, the solid or the liquid, contains the greater amount of energy per particle? In which phase are the particles moving faster? Explain your answer
To learn more about states of matter refer to :
https://brainly.com/question/16982523
#SPJ13
Butane gas (C4H10) burns in oxygen gas to produce carbon dioxide gas and water vapor. Balance the equation for this reaction (in the lowest multiple integers).What are the formulas for the reactants and products?
The balanced chemical equation for the reaction between butane gas and oxygen gas is as follows: 2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O
What is combustion reaction?Combustion reaction is a process wherein a fuel is combined with oxygen, usually at high temperature, releasing heat.
According to this question, a combustion reaction occurs between butane gas and oxygen gas to form carbon dioxide and water vapor.
2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O
The formula of the reactants of this combustion reaction are as follows; C₄H₁₀ and O₂ while the formula of the products are as follows; CO₂ and H₂O.
Learn more about combustion reaction: https://brainly.com/question/12172040
#SPJ1
86. Which electron configuration notation describes an
atom in an excited state?
A. [Ar]4s23d¹04p²
B. [Ne]3s23p5
C. [Kr]5s²4d¹
D. [Ar]4s²3d84p¹
Electron configuration notation describes an atom in an excited state as [Ar]4s²3d84p¹. Option D.
An electron is in an excited state when it temporarily occupies a higher energy state than its ground state. Electrons are excited when additional energy is supplied. When it absorbs a photon or packet of light or collides with a nearby atom or particle.
When an electron absorbs energy and shifts from a lower energy orbital to a higher energy atomic orbital the atom assumes an exciting electronic configuration. Usually an unstable electronic configuration. As a result, the electron returns to the ground state and releases a certain amount of energy. Ground state means the state with the lowest energy. When an electron absorbs energy and pops into an outer orbit, this state is called an excited state.
Learn more about An excited state here:-https://brainly.com/question/13752626
#SPJ1
look at the picture
The different types of neon with varied numbers of neutrons are best referred to as isotopes.
What are isotopes?In chemistry, isotopes are atoms of the same elements. These atoms have the same number of protons in their nuclei. Thus, they have the same atomic number.
However, isotopes of the same elements do not have the same number of neutrons in their nuclei. Thus, isotopes have the same number of protons but different mass numbers because of the difference in the number of neutrons.
Now consider different neon atoms with 10, 11, and 12 neutrons. These atoms are best described as isotopes of neon.
More on isotopes can be found here: https://brainly.com/question/11680817
#SPJ1