ΕΛΑ
1
a
C
Copper(II) nitrate decomposes on heating. The reaction is endothermic.
2Cu(NO),(s) → 2CuO(s) + 4NO2(g) + 0,(9)
Sketch a reaction pathway diagram for this reaction to include the
activation energy
[3]
b Draw an energy cycle to calculate the standard enthalpy change for
this reaction, using enthalpy changes of formation.
[3]
Calculate the enthalpy change for this reaction using the following
enthalpy changes of formation.
AH, [Cu(NO, ),(s)] = -302.9 kJ mol-'
AH, [CuO(s)] =-157.3 kJ mol-!
AH [NO,(g)] = +33.2 kJ mol-!
[3]
d Copper(II) sulfate is soluble in water. A student dissolved 25.0 g of
copper(II) sulfate in 100 cm of water in a polystyrene beaker stirring
all the time. The temperature of the water fell by 2.9 °C.
i Calculate the enthalpy change of solution of copper(II) sulfate.
(specific heat capacity of water = 4.18 Jg1 °C ; relative
molecular mass of copper(II) sulfate = 249.7 g mol-')
[3]
ii Suggest one source of error in this experiment and explain how
the error affects the results.
[2]
[Total: 14]

Un elemento químico, o un elemento, se define como un material que no puede descomponerse ni transformarse en otra sustancia por medios químicos. Cada elemento se identifica según la cantidad de protones que tiene en su núcleo atómico. Se puede crear un nuevo elemento agregando más protones a un átomo.

_________

Espero eso ayude ⚜

ITZY :)

Answer: 0.023 moles of CaO.

Explanation:

The balanced equation tells us that we'll get 2 moles of CaO for every one mole of O2.  Since we have 0.046 moles of O2, we'll get 0.023 moles of CaO.  (2 sig figs)

Answer:

One arrow is positioned in each box according to Hund's Rule which tells us to maximise the number of unpaired electrons in orbitals of the same subshell, and, to give those electrons the same "spin" (parallel spin).

Explanation:

In this exercise we want to calculate the amount of moles, so this is going to be:

[tex](4.6)(10^{-3}) \ mols \ CO_2[/tex]

Knowing that Henry's law is given by:

[tex]C = KHP[/tex]

Where constants are given by:

Before we can find the concentration of CO2 (and hence the moles of CO2), we first need to find its partial pressure.  We look up the vapor pressure of water at 25º and find it to be 0.03 atm.  Since the total pressure is equal to 0.1 atm, this mean the partial pressure of:

[tex]CO_2 = 0.1 \ atm - 0.03 \ atm = 0.07 \ atm[/tex]

Now using Henry's law, we find the concentration:

[tex]C = (0.033)*( 0.07) = (2.31)*(10^{-3})[/tex]

Converting to moles of CO2, we have:

[tex](2.31)*(10^{-3})*( 2) = (4.6)*(10^{-3})[/tex]

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Answer:

Unlike isopropanol, hydrogen peroxide is not a type of alcohol. You might recognize its chemical formula, H2O2, as being similar to that of water (H2O). The difference is that hydrogen peroxide has two oxygen atoms instead of one. That one extra oxygen atom makes it a strong oxidizer.

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Metals have tendency to loose electrons in order to get noble gas configuration, therefore they loose electrons to form Cations (positively charged ions)

for example ~ Sodium forms Na+

And

Non - metals have tendency to gain electrons in order to attain noble gas configuration , hence they gain electron from somewhere and bears a negative charge forming Anion.

for example ~ Chlorine forms Cl-

Answer:

Similar: both processes of cell division; both processes take place in the nucleus of the cell

Different: mitosis divides into 2, meiosis divides into 4; one is the division of body cells and the other is of specifically sex cells

Explanation:

https://byjus.com/biology/mitosis-and-meiosis/

^ this has more info!

Por definición de enlace iónico, covalente y regla del octeto, la relación existente entre la teoría del octeto de Lewis con los enlaces iónicos y  covalentes es que dichos enlaces se producen con el objetivo de completar la última capa de electrones y adquirir estabilidad.

Por un lado, se produce un enlace iónico entre átomos metálicos y no metálicos, donde los electrones se transfieren completamente de un átomo a otro. Durante este proceso, un átomo pierde electrones y otro los gana, formando iones. Por lo general, el metal cede sus electrones formando un catión al elemento no metálico, que forma un anión.

Por otro lado, el enlace covalente es el enlace químico entre átomos donde los electrones se comparten, formando una molécula. Se establecen enlaces covalentes entre elementos no metálicos. El par de electrones compartidos es común a los dos átomos y los mantiene unidos.

En ambos casos se cumple con la regla del octeto, que establece que los átomos de los elementos se enlazan unos a otros en el intento de completar su capa de valencia con ocho electrones. Es decir que los átomos van a tender a ceder o compartir electrones para completar ocho electrones en la capa de valencia mediante un enlace iónico, covalente o metálico.

En otras palabras, el objetivo es tener la configuración electrónica del gas noble más cercano, teniendo así la última capa de electrones completa y adquiriendo estabilidad.

En resumen, la relación existente entre la teoría del octeto de Lewis con los enlaces iónicos y  covalentes es que dichos enlaces se producen con el objetivo de completar la última capa de electrones y adquirir estabilidad.

Aprende más:

Explanation:

after learning more about the position and would

[tex]2\text{Cr(NO}_3\text{)}_3} + 3\text{CuCl}_2 \longrightarrow 2\text{CrCl}_3 + 3\text{Cu(NO}_3\text{)}_2[/tex]

According to the concept of solubility, boiling water and then adding sugar to it will take longer time to dissolve than adding water and sugar together to boil as thermal energy requires to dissolve sugar will be less.

Solubility is defined as the ability of a substance which is basically solute to form a solution with another substance. There is an extent to which a substance is soluble in a particular solvent. This is generally measured as the concentration of a solute present in a saturated solution.

The solubility mainly depends on the composition of solute and solvent ,its pH and presence of other dissolved substance. It is also dependent on temperature and pressure which is maintained.Concept of solubility is not valid for chemical reactions which are irreversible. The dependency of solubility on various factors is due to interactions between the particles, molecule or ions.

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Answer: Place a piece of white paper under the analyte flask throughout the titration

Explanation:

The end point of titration can be made easy by the use of indicators. But we have to be keenly observe for each drop from the burette because, the colour change will be sudden for a drop.

Titration is an analytical technique used to determine the unknown concentration using a standard reagent of known concentration. The standard reagent of known concentration is called titrant and the  one to be determined is called analyte.

Usually analyte is taken in a conical flask and titrant in a burette. The end point of titration is the point at which the reaction is completed in perfect stoichiometry.

In acid-base titrations, the indicators used having different colors in different pH. Hence, the indicator in the analyte will change in color when the acidity of the medium changes. We have to observe keenly for the color change because it happens for any drop.

The adding of titrant from the burette must be dropwise and thus we can get a time to notice the sudden colour change of indicator.

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Answer:

carbohydrates

Explanation:

or carbon dioxide

8%

Explanation:

In a DNA molecule the no. of Adenine bases equal to that of Thymine bases

The no. of Cytosine bases equal to that of Guamine bases.

If we take no. of Thymine bases as x and no. of Cytosine bases as y,

Adenine + Thymine + Cytosine + Guamine = 100

x + x + y+y = 100

2( x+y) = 100

x+y = 50

y=42

therefore x= 50-42 = 8%

Answer:

Explanation:

The new pressure can be found by using the formula for Boyle's law which is

[tex]P_2 = \frac{P_1V_1}{V_2} \\[/tex]

where

P1 is the initial pressure

P2 is the final pressure

V1 is the initial volume

V2 is the final volume

From the question we have

[tex]P_2 = \frac{125\times3.50 }{2.75} = \frac{437.5}{2.75} \\ = 159.090909...[/tex]

We have the final answer as

Hope this helps you

Answer:

mark me brainlest

Explanation:

Electronegativity values generally increase from left to right across the periodic table. Electronegativities generally decrease from top to bottom of a group. The highest electronegativity value is for fluorine.

Answer:

       "Electronegativity increases as you move from left to right across a period because the number of charges on the nucleus increases." (sstudy30 on Quizlet)

Explanation:

    It explains itself haha!

Have a nice day!

    I hope this is what you are looking for, but if not - comment! I will edit and update my answer accordingly. (ノ^∇^)

- Heather

The chemicals found at the crime scene although not mentioned must be Sodium zincate.

Discussion:

An interesting demonstration to show plating and alloys is the conversion of copper coins to silver look-alike coins.

A 'copper' coin when dipped into a solution of sodium zincate in contact with zinc. The coin is plated with zinc and appears silver in colour.

This is a common chemistry classroom trick.

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Answer:

Modern recorders are most commonly pitched at A=440 Hz, but among serious amateurs and professionals, other pitch standards are often found. For the performance of baroque music, A=415 Hz is the de facto standard, while pre-Baroque music is often performed at A=440 Hz or A=466 Hz.

Explanation:

This problem is referring to an anhydrous salt that is derive from a hydrated Epson salt (magnesium sulfate hydrate) and the atom economy is required. However, not enough information is provided, yet we can use the attached file as a reference to provide a methodology of calculation.

To begin with, we need to calculate the [tex]x[/tex] which refers to the degree of hydration of the salt, so that we use the mass before and after heating the sample to figure out the grams and subsequently moles of water that are in there:

[tex]m_w=3.648g-1.782g=1.866g\\\\n_w=0.103molH_2O[/tex]

Next, since 1.782g corresponds to the anhydrous salt, we calculate the moles in such a amount:

[tex]1.782gMgSO_4*\frac{1molMgSO_4}{120.4gMgSO_4}=0.0148mol[/tex]

Then, we divide the moles of water by those of the anhydrous salt to calculte [tex]x[/tex]:

[tex]x=\frac{0.103mol}{0.0148mol} =6.96=7[/tex]

This means the formula of the hydrate is:

[tex]MgSO_4\ 7H_2O[/tex]

Finally, for the atom economy we just divide the molar mass of the anhydrous salt by that of the hydrate:

[tex]A.E=\frac{120.4g/mol}{246.47g/mol} *100\%\\\\A.E=48.8\%[/tex]

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An observer in one of those galaxies see the other galaxy moving away at 400000 km/s.

Relative velocity is the velocity of an object with respect to another object, that is the time rate of change of relative position of one object with respect to another object.

Since two galaxy are moving in opposite directions with a velocity of 200,000 km/s. Hence the relative velocity between the two galaxies is 400000 km/s (200000 + 200000)

Therefore an observer in one of those galaxies see the other galaxy moving away at 400000 km/s.

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Answer:

D 400,000km/s

Explanation:

The orientation of the poles of the magnet on the cars and the large

magnet are like poles.

The correct responses are;

First question

Second question:

Third question:

Fourth question:

Reasons:

Potential energy is the energy an object has due to its location.

Energy is a product of force and distance, and therefore, if the force,

experienced by the object increase, the potential energy of the object

increases.

The strength of a magnetic field, B, is given by the formula;

[tex]\displaystyle B = \frac{\mu_0 \cdot I}{2 \cdot \pi \cdot d}[/tex]

Where;

B = The magnetic field strength

I = Current

d = The distance from the source of the magnet

μ₀ = The permeability of free space = 4·π × 10⁻⁷ T m/A

Therefore, the strength of the magnet is higher closer to the source.

First question

In a magnet, like poles push each other back, and given that the poles of the magnet adjacent to each other are like poles, to get the largest increase in she should move the cars towards the large magnet.

Second question:

The reason why the movement will result in the largest increase in potential energy is because like polls repel each other and the strength of a magnetic field increases closer to the magnet

Third question:

The magnetic force that will act on the roller coaster car moved towards the large magnet, pushes the car in the opposite direction.

Fourth question:

The green cart should be moved from point D to point C to get the largest potential energy

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Answer:

the average mass of the atoms of an element measured in atomic mass unit (amu, also known as daltons, D)

Explanation:

Answer:

Explanation:

Pencils are though formed of wood that acts as a bad conductor of electricity, quite strangely pencils can be electrically charged.

Here pencils have non-metal carbons present in its graphite tip and this makes the pencils charged.

When this pencil is held near the water of the tap, the hydrogen ions get attracted and thereby the water gets attracted to the pencil.

Water, however, is an excellent conductor of electricity and therefore water and electricity are a dangerous combination.

This problem is giving information about the proton concentrations of three solutions at 25 °C. Despite they are not numerically given, we can propose three scenarios to see how to approach the question.

Let the following solutions to come up:

[H⁺] = 2.63x10⁻³ M

[H⁺] = 1.00x10⁻⁷ M

[H⁺] = 4.511x10⁻⁹ M

The first step, will be the calculation of the pH for each solution via:

pH = -log([H⁺])

So that they turn out to be:

pH = -log(2.63x10⁻³ M) = 2.580

pH = -log(1.00x10⁻⁷ M) = 7.000

pH = -log(4.511x10⁻⁹ M) = 8.3457

In such a way, since acidic solutions have a pH below 7, neutral have a pH equal to 7 and basic have it above 7, we infer the first one is acidic, second one is neutral and third one is basic.

Thus, you can reproduce this methodology with the proton concentrations you are given.

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An exothermic process is one that gives off heat.

Explanation:

This heat is transferred to the surroundings. An endothermic process is one in which heat has to be supplied to the system from the surroundings.

Answer:

In chemistry: a pure substance consists only of one element or one compound. a mixture consists of two or more different substances, not chemically joined together.

Hope this helps :)

The general structure of a carboxylic acid is shown by option D.

In organic chemistry, a carboxylic acid is an organic acid that consists of a carboxyl group connected to an R-group. the overall components of carboxylic acid are R−COOH or R−CO₂H, with R referring to the alkyl, alkenyl, aryl, or other institution. Carboxylic acids arise broadly.

A carboxylic acid is a natural compound that incorporates a carboxyl group (C(=O)OH). the general formulation of a carboxylic acid is R–COOH, with R referring to the relaxation of the molecule. A carboxylic acid may be the concept of a mixture between functional corporations: an alcohol institution, related to hydrogen certain to oxygen, which attaches to a carbonyl institution, involving a carbon double sure to oxygen.

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Answer:

The ans is : A. Electron, proton, hydrogen atom, helium atom.

An atom consist of sub atomic particles. The order of particles from least massive to most massive is electron, proton, hydrogen atom, helium atom. The correct option is A.

The particles which are smaller in size than the atom are known as the sub atomic particles. An atom generally contains three sub atomic particles, they are protons, electrons and neutrons. The electrons revolve around the nucleus whereas the protons and neutrons are present at the center of the nucleus.

The protons are positively charged particles whereas the electrons are negatively charged. The neutrons are chargeless. The atomic number of 'H' atom is 1 and that of 'He' atom is 2.

The mass of e⁻ is 9.1 × 10⁻³¹ kg, proton is 1.67 × 10⁻²⁷ kg, 'H' atom is 1.66 × 10⁻²⁴ g, 'He' is 4 g. Thus the order is:

electron, proton, hydrogen atom, helium atom

Thus the correct option is A.

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Answer:

O-H

Explanation:

It is polar covalent bond, because the hydrogen atom has electronegativity about 2.6, and the oxygen atom, electronegativity about 3.6. When the difference in electronegativity of the atoms is between 0.4 and 1.7, the result is a polar covalent bond.