How much of a sample remains after five half-Iives have occurred?
1/5 of the original sarmple
1/25 of the original sarmple
1/32 of the original sample
1/64 of the original sample

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:

4^4, or 256

Explanation:

When dividing numbers with exponents and the same base, you will subtract from the exponents and keep the base the same.

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:

The correct answer is - S- configuration.

Explanation:

Placing the numbers in order of the priorities of each reactant in the reaction is essential to determining the configuration of the reactant and product in the biological oxidation of isotopically labeled ethane.

CH3 - T- D is the correct order of the increasing of the priorties. so this is moving from CH3 to D which is Anti-clockwise which means the configuartion is S as we know clockwise movement is R configuarion and anti-clockwise in S configuartion.

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).

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:

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.

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]

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:

Measurement helps in buying and selling goods

Measurement helps in doing various science

experiment

Measurement is used in our daily life

Measurement is essential for making roads, bridge etc

Answer:

a.) x = 5

Explanation:

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:

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:

Answer:

Decyne: C10H18

Hope it helps! please mark me brainliest..

Merry Christmas good day

The general formula for alkynes is CnH2n-2

the number of carbon atoms is 10 so the number of hydrogen atoms will be 10*2-2=20-2=18hydrogen atoms

the molecular formula for this alkyne is :

C₁₀H₁₈ which is called decyne

Answer:

Explanation:

The volume of a substance when given the density and mass can be found by using the formula

[tex]volume = \frac{mass}{density} \\[/tex]

From the question we have

[tex]volume = \frac{20}{4} \\ [/tex]

We have the final answer as

Hope this helps you

Answer: Climax Commuity.

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

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:

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:

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:

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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digestion

does that answer it?

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:

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:

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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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:

860 cm/s

Explanation:

Let P = momentum of wrench-man system before throwing the wrench and P' = momentum of wrench-man system before throwing the wrench.

From the law of conservation of momentum,

P = P'

P = 0 (since both Astronaut and wrench were initially stationary) and P' = m₁v₁ + m₂v₂ where m₁ = mass of wrench = 4g = 0.004 kg v₁ = velocity of wrench after releasing the wrench = -15 m/s m₂ = mass of Astronaut = 70 kg and v₂ =  velocity of Astronaut after releasing the wrench.

So, P = P'

0 = m₁v₁ + m₂v₂

-m₁v₁ = m₂v₂

dividing both sides by m₂, we have

v₂ = -m₁v₁/m₂

substituting in the values of the variables, we have

v₂ = -0.004 kg × (-15 m/s)/70 kg

= 0.06 kgm/s ÷ 70 kg

= 8.6 × 10⁻⁴ m/s

= 860 × 10⁻² m/s

= 860 cm/s

Answer:

The forces are equal and applied in the opposite direction

Explanation:

Study island 100