Which of these is an example of a chemical change?

Answer:

Los dos óxidos que forma el cobre son óxido de cobre (I) y óxido de cobre (II) (Cu₂O y CuO, respectivamente).

Explanation:

El cobre posee dos estados de oxidación más comunes, los cuales son +1 y +2.

En contacto con aire el cobre se puede oxidar para dar lugar al óxido cuproso u óxido de cobre (I):

4Cu + O₂ → 2Cu₂O

Dicha oxidación también puede dar lugar a la formación del óxido cúprico u óxido de cobre (II):

2Cu + O₂ → 2CuO

La formación del óxido cúprico se favorece a temperaturas mayores a la del ambiente (por encima de los 300 °C).

Por lo tanto, los dos óxidos que forma el cobre son óxido de cobre (I) y óxido de cobre (II) (Cu₂O y CuO, respectivamente).  

Espero que te sea de utlidad!

19. place moth balls in the closet and observe after several days.

20. whenever wax or a candle burns it turns from solid to liquid but again at room temperature it turns to solid

21. evaporation, condensation, precipitation

22. it produces new substances

23. vinegar Bubbles when baking soda is added

24. steam

Answer: A mass of 124457.96 g ammonia is produced by reacting a 450 L sample of nitrogen gas at a temperature of 450 K and a pressure of 300 atm.

Explanation:

Given: Volume = 450 L

Temperature = 450 K

Pressure = 300 atm

Using ideal gas equation, moles of nitrogen are calculated as follows.

PV = nRT

where,

P = pressure

V = volume

n = no. of moles

R = gas constant = 0.0821 L atm/mol K

T = tempertaure

Substitute values into the above formula as follows.

[tex]PV = nRT\\300 atm \times 450 L = n \times 0.0821 L atm/mol K \times 450 K\\n = \frac{135000}{36.945}\\= 3654.08 mol[/tex]

According to the given equation, 1 mole of nitrogen forms 2 moles of ammonia. So, moles of ammonia formed by 3654.08 moles of nitrogen is as follows.

[tex]2 \times 3654.08 mol\\= 7308.16 mol[/tex]

As moles is the mass of substance divided by its molar mass. So, mass of ammonia (molar mass = 17.03 g/mol) is as follows.

[tex]Moles = \frac{mass}{molar mass}\\7308.16 = \frac{mass}{17.03 g/mol}\\mass = 124457.96 g[/tex]

Thus, we can conclude that a mass of 124457.96 g ammonia is produced by reacting a 450 L sample of nitrogen gas at a temperature of 450 K and a pressure of 300 atm.

Answer:

heat energy to keep you warm and light energy to be able to read your book

Explanation:

Answer:

the reaction is spontaneous

Answer:

the answer is c kept in blue and with light

Answer:

sry I don't know the answer

Answer:

more

Explanation:

seems like you did not finish the questions

Answer:

5 kg of feather

Explanation:

Answer:

λ = 2.38 × 10^(-7) m

Explanation:

We are given the work function for palladium as 503.7 kJ/mol.

Now let's convert this to KJ/electron.

We know from avogadro's number that;

1 mole of electron = 6.022 × 10^(23) electrons

Thus,

503.7 kJ/mol = 503.7 × 1/(6.022 × 10^(23)) = 8.364 × 10^(-22) KJ/electron = 8.364 × 10^(-19) J/electron

Formula for energy of a photon is;

E = hv

Where;

h is Planck's constant = 6.626 × 10^(-34) J.s

v is velocity

Now, v = c/λ

Where;

c is speed of light = 3 × 10^(8) m/s

λ is wavelength of light.

Thus;

E = hc/λ

Making λ the subject, we have;

λ = hc/E

λ = (6.626 × 10^(-34) × 3 × 10^(8))/(8.364 × 10^(-19))

λ = 2.38 × 10^(-7) m

Answer:

Ca + Pb(NO3)2 → Pb + Ca(NO3)2

Explanation:

This is an oxidation-reduction (redox) reaction:

PbII + 2 e- → Pb0

(reduction)

Ca0 - 2 e- → CaII

(oxidation)

Pb(NO3)2 is an oxidizing agent, Ca is a reducing agent.

Answer:

8.3 × 10³ mL

Explanation:

Step 1: Calculate the mass of water that contains 100 mg of Pb

The concentration of Pb in the sample is 0.0012% by mass, that is, there are 0.0012 g of Pb every 100 g of water. The mass of water that contains 100 mg (0.100 g) of Pb is:

0.100 g Pb × 100 g Water/0.0012 g Pb = 8.3 × 10³ g Water

Step 2: Calculate the volume corresponding to 8.3 × 10³ g of water

Since the solution is diluted, we will assume the density of the sample is equal than the density of water (1 g/mL).

8.3 × 10³ g × 1 mL/1 g = 8.3 × 10³ mL

The volume of the water in milliliters contains 100 mg of Pb is;

V =  8.3 × 10³ mL

We are given the concentration of Pb in the sample as 0.0012% by mass.

That means that there are 0.0012 g of Pb in every 100 g of water.

Thus, the mass of water that contains 100 mg (0.100 g) of Pb is calculated as;

(0.100 g Pb × 100 g of Water)/0.0012 g of Pb = 8.3 × 10³ g of Water

Now, we know that the density of water (1 g/mL) but we are not given the density of the sample.

Thus, since the solution is diluted we can equally say that;

Density of sample = 1 g/mL

Formula for Volume is;

V = mass/density

Thus;

V = 8.3 × 10³ g/1 g/mL

V = 8.3 × 10³ mL

Read more about Volume of solution at; https://brainly.com/question/17055828

Answer:

Electric current

Hydrogen and oxygen gas

Explanation:

Electrolysis is defined as a method of separation whereby an electric current is introduced into compounds to separate them . The electric current used here is a direct electric current (DC) and it makes the compound to be spit into its' component elements.

Now, in the case of water like it says in the question. Water is a mixture of hydrogen and oxygen gas. Thus, when electric current is passed through water which has an Electrolyte, it makes the water to decompose into its compound elements which are hydrogen and oxygen.

Answer:

=0.15M

Explanation:

To get the moles of the unknown LiOH, calculate the number of moles of HCl in 12.3mL.

Using the stoichiometric coefficient, mole ratio 1:1.

This means that the number of moles is the same. This number of moles is contained in 18mL. Then Calculate the molarity (concentration) which is in 1000mL

See the explanation from the image I have shared with you for calculations.

Explanation:

Science, any system of knowledge that is concerned with the physical world and its phenomena and that entails unbiased observations and systematic experimentation. In general, a science involves a pursuit of knowledge covering general truths or the operations of fundamental laws.

Answer:

R2S this is because sodium has one 1 valence and sulfur has valence of 2 so when they combine theyinterchange their valence

Answer:

D. 450 J/kgK

Explanation:

Using the formula as follows:

Q = m × c × ∆T

Where:

Q = amount of heat absorbed/released (J)

m = mass of substance (g)

c = specific heat capacity

∆T = change in temperature (°C)

According to the information provided in this question:

Q = 267.3 kJ = 267300J

m = 18kg

∆T = 318K - 285K = 33K

c = ?

Q = m × c × ∆T

c = Q ÷ m∆T

c = 267300 ÷ 18 × 33

c = 267300 ÷ 594

c = 450 J/kgK

Answer:

D

Explanation:

The first ionization energy is the minimum energy required to remove the most loosely bound electron from an atom.

Good luck!

Answer:

Increased surface area - finely divided solute

like dissolves like - matching polarity

temperature - rate proportional to kinetic energy

stirring spreads - solute throughout solution

Answer:

80 m/s.

Explanation:

NOTE: This is a physics question. However, the solution to the question given below:

From the question given above, the following data were obtained:

Acceleration (a) = 2 m/s²

Initial velocity (u) = 20 m/s

Time (t) = 30 s

Final velocity (v) =?

The final velocity of the train can be obtained as shown below:

v = u + at

v = 20 + (2 × 30)

v = 20 + 60

v = 80 m/s

Therefore, the final velocity of train is 80 m/s.

Answer:

C. the energy used to hold the nucleus together

Answer: lysocline

Explanation:

Lysocline is the depth in the ocean at which calcareous skeletal material first begins to dissolve. It is the depth of the ocean whereby the dissolution rate of calcite has a dramatic rise.

Lysocline is also referred to as the transition zone upper bound where the CaCO3 content drops.

Answer:

i hope it will help you

Explanation:

there will be 7 electrons and 9 protons will have 2+ charge.

Answer:

melting, freezing, sublimation, deposition, condensation, and vaporization. These changes

Explanation:

hope it helps...i dont know if its right but i hope it helps

Answer:

name a food that contain an acid

1. nuts

2. dairy

3. grains

3. meat

these are the foods which contains acids.

hope its helps you

have a great day keep smiling be happy stay safe.

Answer:xl/ck xLKsx

Explanation:sl/cs c/ls

Answer:

0.241 M

Explanation:

We'll begin by writing the balanced equation for the reaction. This is given below:

HBr + NaOH —> NaBr + H₂O

From the balanced equation above,

The mole ratio of acid, HBr (nₐ) = 1

The mole ratio of base, NaOH (n₆) = 1

Finally, we shall determine the concentration of the NaOH solution. This can be obtained as follow:

Volume of base, NaOH (V₆) = 20 mL

Volume of acid, HBr (Vₐ) = 24.1 mL

Concentration of acid, HBr (Cₐ) = 0.2 M

Concentration of base, NaOH (C₆) =?

CₐVₐ / C₆V₆ = nₐ/n₆

0.2 × 24.1 / C₆ × 20 = 1/1

4.82 / C₆ × 20 = 1

Cross multiply

C₆ × 20 = 4.82

Divide both side by 20

C₆ = 4.82 / 20

C₆ = 0.241 M

Therefore, the concentration of the NaOH solution is 0.241 M

Answer:

The higher its electronegativity, the more an element attracts electrons.

Explanation:

Electronegativity is a property that describes the tendency of an atom to attract electrons (or electron density) toward itself. An atom's electronegativity is affected by both its atomic number and the size of the atom.

Answer:

use this formula it will help u .

Explanation:

If 60 ml of ethanol is diluted to a final volume of 400 ml, you create a 35 % ethanol solution.

First, realize that you creating a solution with that contains a polar solute (ethanol) with a polar solvent (water). Remember that "like dissolves like."

If you pour 60 ml of ethanol in a volumetric flask, you add 340 ml of water to dilute this solution to a final volume of 400 ml.

Volumetric flasks are designed to make or dilute solutions to specified final volume.

Since you have 60 ml of ethanol in a total solution of 400 ml, the percentage of ethanol is 35 %.

This result is obtained in the following manner.

ml/400. ml. = .35

.35 x 100% = 35 %