What is the half‑life of an isotope that decays to 25% of its original activity in 85.8 h

Answer:

N(Au) = 1,20 × 10²²

Explanation:

1) n(Au) = m ÷ M = 4.60 g ÷ 197 g/mol = 0,02 mol

2) N(Au) = n(Au) × N(a) = 0,02 × 6.02*10²³ = 1,20 × 10²²

Answer:

See Down

Explanation:

2Al2O3 = 4Al + 3O2 (Decomposition)

31.5/101.961g = 0.3089mol

(0.3089mol/2) * 4 = 0.61788 mole of Al

0.61788 mole * 6.022x10^23 atoms/mol = Your answer

Answer:

The steps involved in determining a Molecular Formula are: Find the mass of the empirical formula. Divide the molecular mass by the mass of the empirical formula. Multiply each subscript in the empirical formula by the answer.

Explanation:

Answer:

False

Explanation:

Groundwater and surface water have a relationship.

Groundwater is the water that is contained in a subsurface layer of an underlying soil/rock whereas surface water is that found in a lake, river or some other surface cavities.

However, when groundwater is discharged to surface water bodies, it is said to be surface water. Thus the statement asked is false.

Answer:

Speed is the time rate at which an object is moving along a path, while velocity is the rate and direction of an object's movement. Put another way, speed is a scalar value, while velocity is a vector.

Explanation:

Hope it is helpful.....

Answer:

6.9 hours

Explanation:

In order to solve this problem we'll convert 837 km to miles (another option would be to convert 75 mi/hr to km/hr). To make said conversion we'll use the given conversion factor:

Finally we calculate the time required to travel said distance at a constant speed of 75 mi/hr:

The amount of time it would take to travel 837 km is equal to 7 hours.

Given the following data:

To determine the amount of time it would take to travel 837 km:

First of all, we would convert the value of the distance in kilometers to miles as follows:

Conversion:

1.61 km = 1 mile

837 km = X mile.

Cross-multiplying, we have:

[tex]X=\frac{837}{1.61}[/tex]

X = 519.88 miles.

Mathematically, time is given by this formula:

[tex]Time = \frac{distance}{speed}[/tex]

Substituting the given parameters into the formula, we have;

[tex]Time = \frac{519.88}{75}[/tex]

Time = 6.93 ≈ 7 hours.

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Answer: BI

because of rection progress

Explanation:

Answer:

MM = 225.11 g/mol

Explanation:

In this case, let's analyze the data.

We have a 15.2 mg of an unknown electrolyte in 150 mL of solution. The osmotic pressure is 8.44 Torr, and we want the molecular mass of the unknown.

The osmotic pressure can be calculated using the following expression:

π = CRT   (1)    

π: osmotic pressure (8.44 Torr * 1 atm / 760 Torr = 0.011 atm)

C: Concentration of the unknown in the solution

R: universal constant of gases (0.082 L atm / K mol)

T: temperature in Kelvin (25 + 273 = 298 K)

From this expression, we can either solve for C, and then use another expression to calculate the molecular mass, or we can just replace the expressions in the above formula, to get the direct molecular mass. In this case, we'll follow the second method.

Concentration or molarity of a substance can be calculated using:

C = moles / V  (2)

And moles can be calculated using this expression:

moles = m / MM   (3)

Replacing (3) in (2), and then in (1) we have:

C = m / MM * V

π = m * RT / MM * V   (4)

and now, we can solve for MM:

MM = mRT / π V  (5)

Now, we just need to replace the given data into the above expression to get the value of the molecular mass:

MM = (15.2 / 1000) * 0.082 * 298 / 0.011 * 0.150

Hope this helps

Answer:

5.68×10¯¹⁰ m

Explanation:

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

Energy (E) = 3.50×10¯¹⁶ J

Wavelength (λ) =?

Energy (E) and wavelength (λ) are related according to the following formula:

E = hv/λ

Where

E => is the energy

h => is the Planck's constant

v => is the velocity of electromagnetic radiation

λ => is the wavelength of the radiation.

With the above formula, we can obtain the wavelength of the radiation as follow:

Energy (E) = 3.50×10¯¹⁶ J

Planck's constant (h) = 6.63×10¯³⁴ Js

Velocity (v) = 3×10⁸ m/s

Wavelength (λ) =?

E = hv/λ

3.50×10¯¹⁶ = 6.63×10¯³⁴ × 3×10⁸ / λ

3.50×10¯¹⁶ = 1.989×10¯²⁵/ λ

Cross multiply

3.50×10¯¹⁶ × λ = 1.989×10¯²⁵

Divide both side by 3.50×10¯¹⁶

λ = 1.989×10¯²⁵ / 3.50×10¯¹⁶

λ = 5.68×10¯¹⁰ m

Thus, the wavelength of the radiation is

5.68×10¯¹⁰ m

Answer:

The independent and dependent variable for the following are as follows:

a. Temperature and amount of dissolved oxygen

b. pH and SO2 solubility/amount

c. H2SO4 concentration and voltage output/performance of battery

Explanation:

In an experiment;

- Independent variable is the variable that the experimenter manipulates or changes in order to get a measurable response.

- Dependent variable is the variable that the experimenter measures based on its response to changes made to the independent variable.

A). In this experiment, a student is trying to investigate the amount of dissolved oxygen in a local pond in response to changes in temperature. Hence, the independent variable is the TEMPERATURE while the dependent variable is the AMOUNT OF DISSOLVED OXYGEN.

B). In this experiment, a wine producer would like to explore if pH affects the solubility of SO2 in the wine by measuring the amount of SO2 in the wine solution over a range of pH values. Hence, the independent variable is the pH while the dependent variable is the SO2 SOLUBILITY OR AMOUNT.

C). In this experiment, a researcher wishes to determine the optimal H2SO4 concentration for the best performance of the battery, as measured by the voltage output. Hence, the independent variable is the CONCENTRATION OF H2SO4 while the dependent variable is the VOLTAGE OUTPUT or PERFORMANCE of the battery.

Answer:

Drycell and car battery

Explanation:

Is it only one answer because I think both of these are redox reactions.

The type of solutions which are appearing cloudy are called colloids. Therefore, option a is correct.

Colloids are mixtures in which particles of one substance are evenly dispersed throughout another substance, creating a stable mixture. The particles in a colloid are larger than those found in a solution, but smaller than those found in a suspension.

Colloids can be found in various states of matter, including solid, liquid, and gas, and they can be formed from a wide range of substances, such as polymers, metals, and biological molecules.

One important characteristic of colloids is their ability to scatter light. This phenomenon, known as the Tyndall effect, occurs when light passes through a colloid and is reflected by the particles, causing the mixture to appear cloudy or hazy.

Colloids also exhibit unique properties related to their size and shape, such as viscosity, surface tension, and Brownian motion. They appear cloudy in nature.

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Answer:

0.03 M

Explanation:

The computation of the molarity of the diluted HCI is given below:

As we know that

(M1) × (V1) = (M2) × (V2)

Now

(M2) = {(M1) × (V1)} ÷ (V2)

or

Molarity of the diluted HCl,(M2) is

= {6 × 25} ÷ 5000

= 0.03 M

Answer:

Mole percent of Ethanol = 0.5986 * 100 = 59.86%

Explanation:

Mole percent is the percentage of the total moles that is of a particular component.

We have to covert the ethanol and water to moles. This is given by the equation;

Number of moles =  Mass / Molar mass

Ethanol;

Number of moles = 71 / 46.07  = 1.5411 mol

Water;

Number of moles = 18.6 / 18  = 1.033 mol

Total mol = 1.5411 mol + 1.033 mol =  2.5741 mol

Mole percent of Ethanol = Number of moles /(Ethanol) / Total moles   * 100

Mole percent of Ethanol =  1.5411 mol / 2.5741 mol   * 100

Mole percent of Ethanol = 0.5986 * 100 = 59.86%

Answer:

10.3 g Li) / (6.9410 g Li/mol) x (1 mol Li3PO4 / 3 mol Li) / (0.750 mol/L Li3PO4) = 0.6595 L = 660. mL

Explanation:

Answer:

High temperatures

Explanation:

NaHCO₃ (8) + HCH,O₂ (aq) → H₂O (l) + CO₂ (g) + NaC,H₃O₂ (aq)

As the flask gets cooler to the touch as the reaction proceeds, the reaction is endothermic. This means that ΔH is positive (ΔH>0).

As a gas is formed (bubbles are formed), ΔS is positive (ΔS>0).

In terms of ΔG:

In order for the reaction to be thermodynamically favorable, ΔH has to be negative, thus:

The greater the temperature, the easier it would be for TΔS to be greater than ΔH.

Answer:

Ionic Substance is....

Explanation:

In chemistry, an ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. The compound is neutral overall, but consists of positively charged ions called cations and negatively charged ions called anions.

Answer:

the theory of evolution states that all living things which exist today, and many more that are now extinct, evolved from simple life forms which first developed 3 billion years ago.

Explanation:

Answer:

Oxygen

Explanation:

In photosynthesis, solar energy is harvested and converted to chemical energy in the form of glucose using water and carbon dioxide. Oxygen is released as a byproduct.

Answer:

the answer is a) oxygen

Explanation:

when plants are performing photosynthesis they take in carbon dioxide given out by humans and animals which is the balance of nature and give out oxygen. in this process sunlight and chlorophyll is also involved!!!!

I hope I cleared your doubt :)

Answer:

Hello your question is poorly written hence i will give you a more general answer

answer :  The reason why it is desirable to use an excess of barium ion in the precipitation is to form the compound needed,

Explanation:

Natural Precipitation occurs when condensed atmospheric water vapor falls due to the gravitational pull exerted on it by the clouds. precipitation can be in various forms like ; rain , ice pellets and snow . e.t.c

Hence the reason why it is desirable to use an excess of barium ion in the precipitation is to form the compound needed,

Also in order to form the precipitation, we will also add excess of barium ion which will help form the required precipitate and also  filter out the mass of Sulphate.

Answer:

. 750 M

Explanation:

Answer:

Explanation:

You just use the balance mole numbers from the equation.

moles HCl needed/16 from the balanced equation ==> 6KCl/2 from equation

x / 16 = 6/2            Multiply both sides   by 16

x = 16 * 6 / 2

x = 48

You need 48 mols of HCl

Hello. Your question is missing data, which makes it difficult to answer it with exactness, but I will try to help you in the best possible way.

If the reaction absorbs energy it means that the reaction is endothermic. This is because endortemic reactions are those that absorb energy from the environment, as opposed to exothermic reactions that release energy into the environment.

In that case, if the reaction is absorbing energy, it is appropriate for the water bath temperature to drop.

Answer:

A.

Explanation:

The potential energy of the roller coaster increases as the coaster goes up a hill and can be converted to kinetic energy.

Answer: the electrostatic potential energy is -3.26 × 10⁻¹⁸ J

Explanation:

Given the data in the question;

I think the value of electrostatic potential energy of calcium sulfide CaS formed will be less(more negative) than KCl because the Ca2+ and S2- ions has more charge that is +2 and -2 respectively when compared to Kcl which has +1 and -1 charge.so it will be more negative.

radius = r[tex]_{ca+2}[/tex] + r[tex]_{s-2}[/tex] = 100 + 184 = 284 pm = 2.84 × 10⁻¹⁰ m

we know that; k = 2.31 × 10⁻²⁸ J

q1 = 2  ( charge on Ca⁺² )

q2 = -2( charge on S⁻²)

so

Ep = k × q1q2/r

so we substitute

Ep = 2.31 × 10⁻²⁸ × (+2×-2) / 2.84 × 10⁻¹⁰

Ep = (2.31 × 10⁻²⁸ × -4) / 2.84 × 10⁻¹⁰

Ep = -9.24 × 10⁻²⁸ / 2.84 × 10⁻¹⁰

Ep = -3.26 × 10⁻¹⁸ J

Therefore, the electrostatic potential energy is -3.26 × 10⁻¹⁸ J

Based on the data provided, the electrostatic potential energy is -3.26 × 10⁻¹⁸ J

The electrostatic potential energy is the work done in moving the charge from infinity to that point against the electric field.

The electrostatic potential energy between any two charges q1, q2 separated by distance r is derived from Coulomb’s law and mathematically given as:

where

From the data provided:

ionic radii of Ca2+ r1 = 100 pm

ionic radii of S2– = 184 pm.

Chargeon Ca2+ = +2

Charge on S2_ = -2

From the data above, it most likely that the value of electrostatic potential energy of calcium sulfide CaS formed will be less(more negative) than KCl because the Ca2+ and S2- ions has a greater charge of +2 and -2 respectively compared to Kcl which has +1 and -1 charge.

Calculating the electrostatic potential energy, Ep:

radius = r1 + r2 = 100 + 184 = 284 pm

r = 2.84 × 10⁻¹⁰ m

k = 2.31 × 10⁻²⁸ J

q1 = 2  ( charge on Ca⁺² )

q2 = -2( charge on S⁻²)

Then:

Ep = k × q1q2/r

Substituting the values above in the equation:

Ep = 2.31 × 10⁻²⁸ × (+2 ×-2) / 2.84 × 10⁻¹⁰

Ep = (2.31 × 10⁻²⁸ × -4) / 2.84 × 10⁻¹⁰

Ep = -9.24 × 10⁻²⁸ / 2.84 × 10⁻¹⁰

Ep = -3.26 × 10⁻¹⁸ J

Therefore, the electrostatic potential energy is -3.26 × 10⁻¹⁸ J.

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Explanation:

i believe this is right. my bad if its not

Answer:

Explanation:

Molal freezing point depression constant of butanol Kf = 8.37⁰C /m

ΔTf = Kf x m , m is no of moles of solute per kg of solvent .

mol weight of butanol = 70 g

235.1 g of butanol = 235.1 / 70 = 3.3585 moles

3.3585 moles of butanol dissolved in 4.14 kg of water .

ΔTf = 8.37 x 3.3585 / 4.14

= 6.79⁰C

Depression in freezing point = 6.79

freezing point of solution = - 6.79⁰C .