define what is halflife​

Answer:

[tex]pH=3.95[/tex]

Explanation:

Hello,

In this case, by using the Henderson-Hasselbach equation we can compute the pH as follows:

[tex]pH=pKa+log(\frac{[base]}{[acid]} )[/tex]

Whereas the concentration of the acid (HCNO) and the base (NaCNO) are computed by considering the given volume:

[tex][base]=\frac{0.410mol}{2.0L}=0.205M[/tex]

[tex][acid]=\frac{0.130mol}{2.0L}=0.065M[/tex]

Therefore, the pH turns out:

[tex]pH=-log(3.5x10^{-4})+log(\frac{0.205M}{0.065M} )\\\\pH=3.95[/tex]

Regards.

Answer:

Coarse and fine adjustment The coarse adjustment knob should only be used with the lowest powerobjective lens. Once it is in focus, you will only need to use the fine focus. Using the coarse focus withhigher lenses may result in crashing the lens into the slide.

Answer:

Metaphase - this is when the chromosomes align

During Metaphase of mitosis, the chomosomes align at the middle part of the cell. Henc ethe correct option is (C).

In cell biology, mitosis is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei.

Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maintained. Therefore, mitosis is also known as equational division.

During metaphase, the nucleus dissolves and the cell's chromosomes condense and move together, aligning in the center of the dividing cell.

At this stage, the chromosomes are distinguishable when viewed through a microscope.

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Answer:

A They are attracted to a magnet

Answer:

not sure but I think it's c

Answer:

Sounds great

Explanation:

Probably fake but you never know do you

Answer:

0.000399316  g

Explanation:

We can start with the molar fraction for each isotope:

We can say that the abudandance of [tex]^2^3Na[/tex] is an unknow value "X" and the molar fraction of [tex]^2^2Na[/tex] is "Y". We have to keep in mind that the molar fractions can be added:

Y + X = 1

So, we can put the molar fraction of [tex]^2^2Na[/tex] in terms of [tex]^2^3Na[/tex], so:

Y=1-X

So, we will have the molar fraction of each isotope:

[tex]^2^2Na[/tex]: X-1

[tex]^2^3Na[/tex]: X

And the atomic mass:

[tex]^2^2Na[/tex]: 21.9944

[tex]^2^3Na[/tex]: 22.9898

If we multiply the molar mass by the each atomic mass of each isotope we will have:

[tex] 22.9898*(X)~+~21.9944*(X-1)~=~22.9785[/tex]

Now we can solve for "X" :

[tex]22.9898X~+~21.9944X~-21.9944~=~22.9785[/tex]

[tex]44.9842X-21.9944~=~22.9785[/tex]

[tex]44.9842X~=~22.9785~+~21.9944 [/tex]

[tex]44.9842X~=~44.9729 [/tex]

[tex]X~=~\frac{44.9729}{44.9842}[/tex]

[tex]X~=~0.999749 [/tex]

The molar fraction of [tex]^2^3Na[/tex] is 0.999749. Now we can calculate the molar fraction of [tex]^2^2Na[/tex], so:

[tex]Y~=~1-0.999749~=~0.000251 [/tex]

Now, if we multiply the molar fraction by the mass we can find the mass of [tex]^2^2Na[/tex], so:

[tex]mass~of~^2^2Na~=~1.5909~g*0.000251~=~0.000399316~ g[/tex]

The mass of [tex]^2^2Na[/tex] is 0.000399316  g

I hope it helps!

Answer:

33600 J

Explanation:

From the question,

ΔH = cm(t₂-t₁)..................... Equation 1

Where, ΔH = Enthalpy change of water, c = specific heat capacity of water, m = mass of water, t₂ = Final temperature of water, t₁ = Initial temperature of water

Given: c = 4200 J/kg.°C, m = 100 g = 0.1 kg, t₂ = 50°C, t₁ = -30°C

Substitute these values into equation 1

ΔH = 4200(0.1)(50+30)

ΔH = 420(80)

ΔH = 33600 J

Answer:

True

Explanation:

The correct option is; True.

Unimolecular elementary steps in a reaction requires only one reactants, they are usually decomposition reactions. They take the general form;

A --> B + C

Answer:

a. O₂ is limiting reactant

b. 5.68g P₄O₁₀ are produced

c. 5.83g P₄O₆ are left in the reaction container

Explanation:

Based in the first reaction,

P₄ + 3O₂ → P₄O₆

1 mole of P₄ reacts with 3 moles of oxygen

Initial moles of P₄ and O₂ are:

Moles P₄ (Molar mass: 124g/mol):

5.77g P₄ * (1mol / 124g) = 0.0465 moles P₄

Moles O₂ (32g/mol):

5.77g O₂ * (1mol / 32g) = 0.180 moles O₂

For a complete reaction of 0.0465 moles P₄ are required:

0.0465 moles P₄ * (3 moles O₂ / 1 mol P₄) = 0.140 moles of O₂

That means will remain 0.040 moles of O₂ and there are produced 0.0465 moles of P₄O₆

For the second reaction:

P₄O₆ + 2O₂ → P₄O₁₀

2 moles of oxygen reacts per mole of P₄O₆

For a complete reaction of P₄O₆ are required:

0.0465 moles P₄O₆ * (2 moles O₂ / 1mol P₄O₆) = 0.093 moles of O₂. As there are just 0.040 moles of O₂,

b. There are produced:

0.040 moles O₂ * (1 mole P₄O₁₀ / 2 moles O₂) = 0.020 moles P₄O₁₀

In mass (Molar mass: 284g/mol):

0.020 moles * (284g / mol) =

c. Also, 0.020 moles P₄O₆ are reacting and will remain:

0.0465 mol - 0.020 mol = 0.0265 moles P₄O₆

In mass (Molar mass: 220g/mol):

0.0265 moles P₄O₆ * (220g / mol) =

Answer:

200x

Explanation:

The total magnification of a microscope depends on the power of the eyepiece and that of the objective lens. It is obtained by multiplying the two factors together.

The total magnification of a microscope can be mathematically expressed as:

Total Magnification = ocular/eyepiece magnification x objective magnification

In the illustration, eyepiece magnification = 10 and objective magnification = 20. Hence,

Total Magnification = 10 x 20 = 200x

The magnification power of the microscope has been 200X. Thus, option B is correct.

A microscope has been the instrument used for the analysis of the magnified image of micro-sized or small objects.

The microscope has been consisted of the objective lens and eyepiece that adjusts the level of magnification of the microscope.

The magnification of the microscope has been the product of the power of the eyepiece and objective lens.

Magnification power = Objective lens power [tex]\times[/tex] Eyepiece power

The given power of objective lens = 20

The power of the eyepiece = 10

Magnification power = 20 × 10

Magnification power = 200X.

The magnification power of the microscope has been 200X. Thus, option B is correct.

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Answer:

The answer to your question is "Displacement " reaction. Here in the reach Zn +HCl ⇒ZnCl2 + H2 zinc replaces the hydrogen to make the zinc chloride and hydrogen gas is produced as the result and liberated.

Answer:the answer is hypothesis

Explanation: that’s the answer

Answer:

435 mL

Explanation:

Step 1: Given data

Step 2: Calculate the final volume of the solution

We want to prepare a diluted solution from a concentrated one. We can calculate the final volume of the solution using the dilution rule.

C₁ × V₁ = C₂ × V₂

V₂ = C₁ × V₁ / C₂

V₂ = 0.500 M × 87.0 mL / 0.100 M

V₂ = 435 mL

Answer:

See explanation

Explanation:

XeF4 has a square planar structure. There are six electron pairs on the valence shell of the central atom. This gives rise to an octahedral geometry based on valence shell electron pair repulsion theory.

There are two lone pairs of electrons present on the central atom, hence the four bond pairs are found to occupy the corners of a square thereby giving a square planar compound. The two lone pairs are found above and blow the plane of the square.

Explanation:

A gas has a temperature of 273.15 K and a pressure of 101.325 kPa. It can be concluded that this gas has reached standard temperature and pressure.

Standard temperature is zero degree celcius which corresponds to 273.15 degree kelvin.

Standard pressure is 760 mmHg which corresponds to 101.325 kPa.

Answer:

a. it has reached standard temperature and pressure

Explanation:

edge 2021

(:

Answer:

NH₃

Explanation:

The hydrogen bond is a specially strong type of dipole-dipole interaction. For a hydrogen bond to occur, a molecule must have a hydrogen atom and a very electronegative atom, such as nitrogen, oxygen or fluorine. The hydrogen atom has a positive charge density while the heteroatom has a negative charge density.

Which of the following molecules can form hydrogen bonds?

NH₃ YES

NaH NO

HI NO

BH₃ NO

CH₄ NO

Answer:

It is becoming more acidic.

Explanation:

The pH scale is a way to express the concentration of hydrogen ions. This scale goes from 0 to 14 and it is adimensional.

The lower the pH, the more acidic the solution. Since the pH of the garden soil of Olivia is decreasing, it is becoming more acidic.

Answer:

Uranium must be purified before it is used as a fuel source

Explanation:

The purer the uranium sample, the more the concentration of uranium in the fuel is.

Whenever uranium is extracted from nature, it contains a lot of impurities. Only a few special nuclear reactors can utilize uranium in this raw state. most of the others have to get uranium to become about 3% pure before they begin using it.

To do this, uranium has to be passed through a series of chemical reactions all with the aim of extracting the other compounds that may be present in the fuel.

Answer:

490 in^3 = 8.03 L

Explanation:

Given:

The engine displacement = 490 in^3

= 490 in³

To determine the engine piston displacement in liters L;

(NOTE: Both in^3 (in³) and L are units of volume). Hence, to find the engine piston displacement in liters (L), we will convert in^3 to liters (L)

First, we will convert in³ to cm³

Since 1 in = 2.54 cm

∴ 1 in³ = 16.387 cm³

If 1 in³ = 16.387 cm³

Then 490 in³ =  (490 in³ × 16.387 cm³) / 1 in³ = 8029.63 cm³

∴ 490 in³ = 8029.63 cm³

Now will convert cm³ to dm³

(NOTE: 1 L = 1 dm³)

1 cm = 1 × 10⁻² m = 1 × 10⁻¹ dm

∴ 1 cm³ = 1 × 10⁻⁶ m³ = 1 × 10⁻³ dm³

If 1 cm³ = 1 × 10⁻³ dm³

Then, 8029.63 cm³ = (8029.63 cm³ × 1 × 10⁻³ dm³) / 1 cm³ = 8.02963 dm³

≅ 8.03 dm³

∴ 8029.63 cm³ = 8.03 dm³

Hence, 490 in³ = 8029.63 cm³ = 8.03 dm³

Since 1L = 1 dm³

∴ 8.03 dm³ = 8.03 L

Hence, 490 in³ = 8.03 L

An engine piston displacement of 490 in³ is equivalent to 8.03 L.

The engine piston displacement is 490 in³ and we want to convert it to liters. Since both of them are units of volume, we will need one or more conversion factors.

A conversion factor is an arithmetical multiplier for converting a quantity expressed in one set of units into an equivalent expressed in another.

We will use the conversion factor 1 in = 2.54 cm.

490 in³ × (2.54 cm/1 in)³ = 8.03 × 10³ cm³

We will use the conversion factor 1 L = 1000 cm³.

8.03 × 10³ cm³ × (1 L/1000 cm³) = 8.03 L

An engine piston displacement of 490 in³ is equivalent to 8.03 L.

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Explanation:

a) Corrosive and b) Reacts with certain metals

Answer:

pH = 7.73

Explanation:

The pKa of the HOCl/KOCl buffer is 7.46. To determine the pH of this buffer we can use H-H equation:

pH = pKa + log [A⁻] / [HA]

pH = 7.46 + log [KOCl] / [HOCl]

Where [] is molarity -or moles- of each compound

Initial moles of HClO and NaClO:

HOCl: 0.500L * (0.12mol / L) = 0.06 moles HOCl

KOCl: 0.500L * (0.080mol / L) = 0.04 moles KOCl

Now, HOCl reacts with KOH producing KOCl:

HOCl + KOH → KOCl + H₂O

The moles of KOH in the reaction are:

2.5x10⁻³L * (10mol /L) = 0.025 moles KOH

That means after the reaction, 0.025 moles of HOCl are consumed and 0.025 moles of KOCl are produced.

And after the reaction, moles are:

Final moles:

HOCl: 0.06mol - 0.025mol = 0.035 mol

KOCl: 0.04mol + 0.025mol = 0.065 mol

Replaing in H-H equation:

pH = 7.46 + log [0.065mol] / [0.035mol]

Answer:

[See Below]

Explanation:

23 or 23.5 ml.

Answer:

Explanation:

The composition of the vapor in mass percent.

According to Dalton's law,

where  is the partial pressure of the gas j,  is the mole fraction of the gas j in the gas mixture and  is the total pressure.

To know the composition of the vapor we must first calculate the molar fractions of the components of the mixture in the vapor:

→  

 →  

If we consider 1 mole of solution then we will have 0.56 mol of benzene and 0.44 mol of toluene in the vapor. In this way, the number of grams of each component in the vapor will be,

The percentage by mass of each component in the vapor will be,

% benzene = (g benzene / g total) x 100% = (43.7 g / (43.7 g + 40.6 g)) x 100% → % benzene = 51.8 %

% toluene = 100 % - % benzene → % toluene = 41.2%

So, the composition of the vapor in mass percent is 51.8 % benzene and 41.2% toluene.

Why is the composition of the vapor different from the composition of the solution?

The composition of the vapor will be different from that of the solution, since the more volatile compound will have a larger molar fraction in the vapor phase than in the liquid phase.

In a mixture with different volatile components the compound that volatilizes more easily is the one that will have greater capacity to escape from the solution in the form of vapor and, therefore, will be in a greater composition in the vapor above the solution.

We can measure this by means of vapor pressure, which is a measure of the volatility of a substance, that is, the capacity of the substance to pass from a liquid to a gaseous state. In the question, benzene is in greater proportion than toluene in the vapor mixture since it has a higher vapor pressure (94.2 torr) than toluene (28.4 torr).

The question is incomplete, the complete question is;

Which is most closely associated with the Lewis dot diagrams for molecules that contain atoms of elements from the boron family, Group 13 (Group IIIA)?

a. elements shown as 3+ ions

b. expanded octets of electrons

c. incomplete octets of electrons

d. odd number of valence electrons

e. kernel electrons promoted to the valance shell

Answer:

incomplete octets of electrons

Explanation:

A Lewis dot structure is a representation of a molecule based on the number of valence electrons on its valence shell. These electrons are shown as dots hence Lewis structures are also called dot electron structures.

For elements of group 13, they mostly form dimeric compounds due to the fact that their compounds possess an incomplete octet of electrons. This is common to group 13 elements, hence the answer above.

Answer:

The answer is Option A = CCl2F2

The chemical formula for an organic molecule is CCl2F2. The correct option is A.

An organic molecule is a complicated compound that is chiefly comprised of carbon atoms bonded with other elements and another carbon atoms.

All lifeforms on Earth are comprised of organic molecules. A molecule is a cluster of atoms which are basically bonded together.

Molecules other than organic molecules is referred to as inorganic molecule. These are basically simple and are not usually encountered in living things.

Although all organic substances encompasses carbon, some substances containing carbon, such as diamonds, are taken as inorganic.

Organic compounds as well as inorganic compounds develops the basis of chemistry.

The chief distinction between organic and inorganic compounds is that organic compounds always contain carbon while most inorganic compounds do not encompass carbon.

Also, perhaps all organic compounds contain carbon-hydrogen or C-H bonds.

Thus, the correct option is A.

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Answer: 252

Explanation:

# turn F to C

C=(F-32)5/9

C=(-5-32)5/9

C=-37 × (5/9)

C= -21

# turn C to K

K=C+273

K=(-21)+273

K=252

Answer:

253 Kelvins

Explanation:

We want to convert -5°F to Kelvins.

First, we must convert -5°F to Celsius. The formula is:

°C= (°F - 32) * 5/9

Plug -5 in for °F.

°C= (-5-32) * 5/9

Solve inside the parentheses first. Subtract 32 from -5.

°C= (-37) * 5/9

Multiply -37 and 5/9.

°C= -20.5555556

-5° F is equal to -20.5555556° C.

Next, convert Celsius to Kelvins. The formula is:

K= °C + 273.15

Plug -20.5555556 in for °C.

K= -20.5555556 + 273.15

Add -20.5555556 and 273.15.

K= 252.594444

Round to the nearest whole number. The 5 in the tenth place tells us to round 252 to 253.

K ≈ 253

-5°F is equal to about 253 Kelvins.

Answer:

105 mg

Explanation:

The following data were obtained from the question:

Original amount (N₀) = 420 mg

Half life (t½) =20 days

Time (t) = 40 days

Amount remaining (N) =..?

Next, we shall determine the rate constant K, for the disintegration.

This can be obtained as follow:

Half life (t½) =20 days

Rate constant (K) =?

K = 0.693/ t½

K = 0.693/20

K = 0.03465 /day

Finally, we shall determine the amount remaining after 40 days as follow:

Original amount (N₀) = 420 mg

Rate constant (K) = 0.03465 /day

Time (t) = 40 days

Amount remaining (N) =..?

Log(N₀/N) = kt/2.3

Log (420/N) = (0.03465 x 40)/2.3

Log (420/N) = 1.386/2.3

Log (420/N) = 0.6026

420/N = antilog (0.6026)

420/N = 4

Cross multiply

420 = N x 4

Divide both side by 4

N = 420/4

N = 105 mg

Therefore, the amount remaining after 40 days is 105 mg.

Answer:

[tex]Ka=1.11x10^{-3}[/tex]

Explanation:

Hello,

In this case, since the ionization of the given HA acid is:

[tex]HA\rightleftharpoons H^++A^-[/tex]

The equilibrium expression is:

[tex]Ka=\frac{[H^+][A^-]}{[HA]}[/tex]

Whereas the concentration of hydrogen ions is compute from the pH=

[tex][H^+]=10^{-pH}=10^{-2.00}=0.01M[/tex]

Which also equals the concentration of [tex]A^-[/tex] and the in general the ionization extent, therefore, the acid ionization constant, Ka, turns out:

[tex]Ka=\frac{0.01*0.01}{0.1-0.01}\\ \\Ka=1.11x10^{-3}[/tex]

Regards.

Answer:

The volume of the rectangular prism is 77.616 cm³

Explanation:

Here is the remaining part of the question:

Part B:

What value should you use as the area of the base when calculating the answer to Part C.

Part C:

Using the correct answer from Part B, calculate the volume of a rectangular prism with a length of 5.6 cm , a width of 2.1 cm , and a height of 6.6 cm Part B answer: 11.76 cm^2

Explanation:

The volume of a rectangular prism is given by:

V = l×w×h

Where V is the volume of the rectangular prism

l is the length of the rectangular prism

and w is the width of the rectangular prism

Recall that the Area (A) of the base of the rectangular prism can be calculated by using

A = l × w

Hence, the volume of the rectangular prism can also be calculated by substituting this into the equation to give

V = A × h

From the question, the correct answer from part B for the area of the base is 11.76 cm^2; and the height (h) is 6.6 cm

Hence, the volume of the rectangular prism is

V = A × h

V = 11.76 cm² × 6.6 cm

V = 77.616 cm³

Answer:

If Jerome is swinging on a rope and transferring energy from gravitational potential energy to kinetic energy,work is being done. Work is said to be done when it transforms energy from one form to another or from one place to another.

Explanation: