HELP please. Only if your POSITIVE

Answer:

b. 2.28 M

Explanation:

The reaction of neutralization of NaOH with H2SO4 is:

2NaOH + H2SO4 → Na2SO4 + 2H2O

Where 2 moles of NaOH react per mole of H2SO4

To solve the concentration of NaOH we need to find the moles of H2SO4. Using the chemical equation we can find the moles of NaOH that react and with the volume the molar concentration as follows:

Moles H2SO4:

45.7mL = 0.0457L * (0.500mol/L) = 0.02285 moles H2SO4

Moles NaOH:

0.02285 moles H2SO4 * (2moles NaOH / 1 mol H2SO4) = 0.0457moles NaOH

Molarity NaOH:

0.0457moles NaOH / 0.020L =

2.28M

Right option:

The concentration of the starting NaOH solution is:

b. 2.28 M

Neutralization reaction:

The reaction of neutralization of NaOH with H₂SO₄ is:

2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

We need to find the moles of H₂SO₄. Using the chemical equation we can find the moles of NaOH.

Moles of H₂SO₄:

45.7mL = 0.0457L * (0.500mol/L) = 0.02285 moles of H₂SO₄

Moles of NaOH:

0.02285 moles H₂SO₄ * (2moles NaOH / 1 mol H₂SO₄) = 0.0457moles NaOH

Molarity of NaOH:

0.0457moles NaOH / 0.020L =2.28M

Thus, the concentration of the starting NaOH solution is: 2.28 M.

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Answer:

0.5 M

General Formulas and Concepts:

Chemistry - Aqueous Solutions

Explanation:

Step 1: Define

2.0 mol glucose

4.0 L glucose solution

Step 2: Find Molarity

Answer:

M = 1.04 M

Explanation:

Given data

Molarity of solution = ?

Mass of HCl = 6.27 g

Volume of solution = 163 mL (163 mL× 1L /1000 mL = 0.163 L)

Solution:

Molarity is used to describe the concentration of solution. It tells how many moles are dissolve in per litter of solution.

Formula:

Molarity = number of moles of solute / L of solution

Number of moles of HCl:

Number of moles = mass/molar mass

Number of moles = 6.27 g / 36.5 g/mol

Number of moles = 0.17 mol

Molarity:

M = 0.17 mol/ 0.163 L

M = 1.04 M

Answer:

4.6

Explanation:

Answer:

B or the second answer.

Explanation:

It's heat transfer and the objects aren't directly touching. B is the only answer that fits.

Hope this helps!

Answer:

b

Explanation:

Answer: Climax Commuity.

Explanation: (hope it’s right! Good luck!)

Answer:

The forces are equal and applied in the opposite direction

Explanation:

Study island 100

Answer:

c

Explanation:

that is my dads answer

A pure substance composed of two or more different elements is a chemical compound.

When two or more atoms are chemically combined, we refer to such a combination as a chemical compound.

Since a chemical compound contains only a given set of elements which are chemically combined together, a chemical compound is also a pure substance.

Hence, a pure substance composed of two or more different elements is a chemical compound.

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The answer to the question, how many photons per second are emitted from the laser is d. 1.84 × 10¹⁵ photons/sec

Since the red laser pointer emits light of wavelength 488 nm, we need to find the energy of each photon from

E = hc/λ where h = Planck's constant = 6.63 × 10⁻³⁴ Js, c = speed of light = 3 × 10⁸ m/s and λ = wavelength of light = 488 nm = 488 × 10⁻⁹ m

Substituting the values of the variables into the equation, we have

E = hc/λ

E = 6.63 × 10⁻³⁴ Js × 3 × 10⁸ m/s ÷ 488 × 10⁻⁹ m

E = 19.89 × 10⁻²⁶ Jm ÷ 488 × 10⁻⁹ m

E = 0.04076 × 10⁻¹⁷ J per photon

E = 4.076 × 10⁻¹⁹ J per photon

Since the laser emits 7.5 × 10⁻⁴ J per second, the number of photons emitted from the laser per second = energy per second/energy per photon

= 7.5 × 10⁻⁴ J per second ÷ 4.076 × 10⁻¹⁹ J per photon

= 1.84 × 10¹⁵ photons/sec

The answer to the question, how many photons per second are emitted from the laser is d. 1.84 × 10¹⁵ photons/sec

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Answer:

Explanation:

To find the number of moles in a substance given it's number of entities we use the formula

[tex]n = \frac{N}{L} \\[/tex]

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question we have

[tex]n = \frac{2.3 \times {10}^{25} }{6.02 \times {10}^{23} } \\ = 38.20598...[/tex]

We have the final answer as

Hope this helps you

Answer:

A

an element made of carbon and oxygen atoms.

So I think the answer is going to be A An element made of carbon and oxygen atoms.

Answer:

2 molecules

Explanation:

I don't know how to explain it

The chemical formula of water is H₂O. Then 1 mole of water weighs 18 gram. Hence, 80 gram of water is equal to 4.4 mole.

Chemical element symbols, numbers, and occasionally other symbols like parentheses, dashes, brackets, commas, and plus and minus signs are used in a chemical formula to represent information about the chemical proportions of the atoms that make up a certain chemical compound or molecule.

It displays the constituent elements and how many atoms of each element are found in a single complex molecule. It also represents the compound's molecular weight.

Water has the chemical formula H₂O. Water weights 18 grams per mole. 80 grams of water are therefore equivalent to 4.4 moles.

Thus, The chemical formula of water is H₂O. 80 grams of H₂ contain 4.4 molecules of water.

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Answer:

40g

Explanation:

Given parameters:

Number of moles  = 1mol

unknown:

mass of Ca  = ?

Solution:

The number of moles of a substance is related to mass using the expression below;

    Mass = number of moles x molar mass

Molar mass of Ca = 40g/mol

     So;

          Mass of Ca = 1 mol  x 40g/mol  = 40g

Answer:

31. C

32. D

33. B

Explanation:

31. A plant cell is an eukaryotic cell i.e. it contains a membrane-bound nucleus, located CENTRALLY. The nucleus is the largest organelle in the plant cell. The cell/plasma membrane bounds the cell while the chloroplast organelle (site of photosynthesis) is also located in the plant cell. Based on this description, the image in OPTION C is correct.

32. Pottasium (K) is a highly reactive group 1 element. As stated in this question, pottasium reacts vigorously with water (H2O). This reactive property of K element is due to its valence electrons. However, elements in the same group as pottasium i.e same column on the periodic table will have the same number of valence electrons, hence, will behave chemically similar. Therefore, elements in the same column as pottasium will react the same way with water.

33. A reactant is a an element/compound in a chemical reaction that gets used up to form new products. They are usually the starting materials located on the left side of any equation. In this equation shown as:

2CuO + C → 2Cu + CO2

CuO and C are the REACTANTS while Cu and CO2 are the products.

Answer:

when the Moon moves into the Earth's shadow

when the Sun, Earth, and Moon are exactly or very closely aligned with the Earth between the other two, and only on the night of a full moon

Explanation:

digestion

does that answer it?

Answer:

The correct answer is - (a) isobutene.

Explanation:

A 1° or primary hydrogen atom is one that is bonded to a 1° carbon atom; a 2° hydrogen atom is one that is connected to a 2° carbon atom; In isobutene only among all the all option having only primary hydrogen atoms. rest have secondary or teritary hydrogen atoms in them

C1∘H3≡CH: (only 1∘ hydrogen atoms)

Answer:

A) To get the pure sawdust u can filter it..

B) The muddy sagment that will form .

C) The clear liquid can divide into 3 layers on the top there will be pure water in middle there will be muddy or dark layer of water and in lower layer there will be the stones or heavy particles of water .

Answer:

4.75 moles of oxygen would be consumed by water

Explanation:

Given data:

Mass of water produced = 68.1 g

Number of moles of oxygen consumed = ?

Solution:

Chemical equation:

C₃H₈ + 5O₂      →    3CO₂ + 4H₂O

Number of moles of water:

Number of moles = mass/molar mass

Number of moles = 68.1 g/ 18 g/mol

Number of moles = 3.8 mol

Now we will compare the moles of water with oxygen.

                H₂O         :            O₂

                  4            :              5

                 3.8          :           5/4×3.8 = 4.75 mol

Answer: 4.75 moles of oxygen

Explanation:

Answer:

E = -0.76 V

Explanation:

The potential between the anode and the cathode is called standard reduction potential. It gives the tendency of the species to get reduced.

The given half reaction is :

[tex]Zn^{2+}(aq)+2e^{-}\rightarrow Zn(s)[/tex]

Zn²⁺ is the reduced form of Zn.

It is a stronger reducng agent.

Its standard reduction potential (E) has a sandard value.

E = -0.76 V

Hence, the correct option is (c).

Periodic table is divided into three metals, non metals and metalloids. The metals are kept on the left side of the periodic table. Gold is a metal which exist in d block.

Metals are those elements which is hard, conduct electricity, ductile, lustrous and malleable.

The properties of gold are:

1.Gold have free electrons that's why they can conduct electricity

2. Since atoms in Gold are very closely packed in a definite crystal so gold is solid. It is not brittle that is it can not be broken down easily

3. Gold does not react with water easily.

4.Gold is denser than water hence it sink in water.

Gold is a transition element. Gold is found in d block of periodic table. Its symbol is Au.

Therefore, Gold is a metal which exist in d block.

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Answer:

The correct answer is 0.3582 M.

Explanation:

Based on the given information, the volume of KOH given is 19.55 ml, the volume of sulfuric acid given is 20.20 ml, and the molarity of sulfuric acid is 0.3467 M. There is a need to find the molarity of KOH.

The formula to use in the given case is,

M1V1 = M2V2

Here M1 is the molarity of KOH, V1 is the volume of KOH, M2 is the molarity of sulfuric acid, and V2 is the volume of H2SO4.

Here V1 is 19.55 ml, M2 is 0.3467 M, and V2 is 2020 ml.

Now putting the values in the equation we get,

M1 * 19.55 = 0.3467 * 20.20

M1 * 19.55 = 7.00334

M1 = 7.00334/19.55

M1 = 0.3582 M

Hence, the molarity of the given KOH is 0.3582.

The molarity of a solution of potassium hydroxide is 0.3582M

To get the molarity of the solution of potassium hydroxide KOH, we will apply the formula;

[tex]C_1V_1=C_2V_2[/tex]

Given the following parameters;

C₂ = 0.3467M

V₂ = 20.20mL

V₁ = 19.55mL

C₁ = ?

Substitute the given parameters into the formula:

C₁ × 19.55 = 0.3467× 20.20

C₁ × 19.55 = 7.00334

C₁ = 7.00334/19.55

C₁ = 0.3582M

Hence the molarity of a solution of potassium hydroxide is 0.3582M

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Answer:

0.2330 grams of solid KCl

Explanation:

In order to find KCl in grams, we need to convert from moles to moles to grams..

However, we are given the volume and the molarity, so first we will use that to convert to moles of AgNO3 (silver nitrate) and then use that to convert to moles of KCl and finally to grams of KCl..

-----------------------------------------------------------------------------------------------------------------

Step 1 -> We need to convert milliliters to liters

(25.0 ml)([tex]\frac{1 L}{1000 mL}[/tex]) = 0.025 L

Step 2 -> Convert from liters and molarity to just moles of AgNO3

(0.025 L)(0.125 [tex]\frac{moles AgNO_{3} }{1 ln soln}[/tex])  =  0.003125  moles [tex]AgNO_{3}[/tex]

**Liters cancel out, so just multiply across...

Step 3 -> Now that we have moles of AgNO3, we will convert to moles of KCl

We will do this using the balanced equation

We see that in the balanced equation, for every mol of AgNO3 that reacts, one mol of KCl will react too. So we will set the dimensional analysis up like the following:

(0.003125 moles AgNO3) * [tex]\frac{1 mol KCl}{1 mol AgNO3}= 0.00312 mol KCl[/tex]

Step 4-> So now that we have moles of KCl, we will just convert to grams

We will do this using the molar mass (atomic mass) of KCl to convert to grams

0.00312 mol KCl * [tex]\frac{74.5513 grams KCl}{1 mol KCl} = 0.2329728125 grams of KCl[/tex]

This can be rounded to 0.2330 grams of KCl

Answer:

Both diseases affect the control of voluntary muscles.

Explanation:

Parkinson's disease is a progressive brain disease that affects movement. It affects the nerve cells that produce dopamine in the part of the brain called substantia nigra. The symptoms include shaking, stiffness, and difficulty with walking, balance, and coordination. Symptoms get worse with time, often leaving people with difficulty walking and talking.

ALS (amyotrophic lateral sclerosis) is a progressive nervous system disease that affects nerve cells in the brain and spinal cord. The first symptoms usually involve muscle weakness, and as the disease progresses, it results in the loss of muscle control.

Scientists don't know the exact cause of these diseases. As the cause is not known, there is no exact way to prevent them. There is no cure for them, either. The treatment is focused on the management of symptoms.

This is why the third option is the correct one.

Answer:

4.5 °C

Explanation:

According to the law of conservation of energy, the sum of the heat lost by the iron and the heat gained by the water is zero.

Qi + Qw = 0

Qi = -Qw   [1]

We can calculate each heat using the following expression.

Q = c × m × ΔT   [2]

where,

Replacing [2] in [1], we get

ci × mi × ΔTi = -cw × mw × ΔTw

ΔTw = -ci × mi × ΔTi / cw × mw

ΔTw = -0.108 cal/g.°C × 700 g × (-30 °C) / 1 cal/g.°C × 500 g

ΔTw = 4.5 °C

Answer:

The particles in the water are always moving

Explanation:

The free energy change(Gibbs free energy-ΔG)=-8.698 kJ/mol

Given

Ratio of the concentrations of the products to the concentrations of the reactants is 22.3

Temperature = 37 C = 310 K

ΔG°=-16.7 kJ/mol

Required

the free energy change

Solution

Ratio of the concentration : equilbrium constant = K = 22.3

We can use Gibbs free energy :

ΔG = ΔG°+ RT ln K

R=8.314 .10⁻³ kJ/mol K

[tex]\tt \Delta G=-16.7~kJ/mol+8.314.10^{-3}\times 310\times ln~22.3\\\\\Delta G=-8.698~kJ/mol[/tex]

a) f2 loses electrons and is oxidised. li gains electrons and is reduced

c)sn2+ loses electrons and is oxidised.Al gains electrons and is reduced

b)br2 loses electrons and is oxidised. I- in KI gains electrons and is reduced