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What makes a White Dwarf Star different from Main Sequence, Giant, and Supergiant stars?

Answer:

solve example number 2 ....

Explanation:

solve examole number 2 .....

Answer:

40,113 years

Explanation:

To find the age of the sample, you need to use the half-life formula:

\(N(t)=N_0(\frac{1}{2})^{t/h\)

In this formula:

------> N(t) = current mass (g)

------> N₀ = initial mass (g)

------> t = time passed (yrs)

------> h = half-life (yrs)

You can plug the given values into the equation and rearrange the formula to find "t".

N(t) = 0.781 g                       t = ? yrs

N₀ = 100 g                           h = 5730 yrs

\(N(t)=N_0(\frac{1}{2})^{t/h\)                                           <----- Half-life formula

\(0.781=100(\frac{1}{2})^{t/5730}\)                                     <----- Insert values

\(0.00781=(\frac{1}{2})^{t/5730}\)                                       <----- Divide both sides by 100

\(log_{1/2}(0.00781)=log_{1/2}((\frac{1}{2})^ {t/5730})\)               <----- Take \(log_{1/2}\) of both sides

\(7.00 = \frac{t}{5730}\)                                                   <----- Solve \(log_{1/2}\)

\(40,113 = t\)                                                   <----- Multiply both sides by 5730

The given sample is 40,113 years .

Half-life, in radioactivity, is the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay.

Half-life formula,

\(\rm N(t)\;=N_0(\dfrac{1}{2})^\frac{t}{t1/2}\)   .......(1)

where,

N(t)=current mass

N₀=initial mass

t=time period

h=half -life

Given,

N(t)=0.781g, t=? yrs, N₀=100g, h=5730 years

\(\rm N(t)\;=N_0(\dfrac{1}{2})^\frac{t}{t1/2}\)

put the values, in ......(1)

0.781=100(1/2) \(t/5730\\\)

log₁/₂(0.00781)=log₁/₂ ( 1/2)\(t/5730\)

7=t/5730

40,113=t

Hence, the given sample is 40,113 years .

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When fluorine gas is put into contact with calcium metal at high temperatures, calcium fluoride (CaF2) is formed.

The chemical equation for the reaction between calcium and fluorine is:

Ca + F2 -> CaF2

The formula for fluorine gas is F2.

To balance the equation for the reaction between calcium and fluorine to form calcium fluoride, you need to ensure that there are the same number of atoms of each element on both sides of the arrow. The balanced equation is:

Ca + F2 -> CaF2

There is 1 atom of calcium on the left side and 1 atom of calcium on the right side, so the equation is already balanced with respect to calcium. There are 2 atoms of fluorine on the left side and 2 atoms of fluorine on the right side, so the equation is also balanced with respect to fluorine.

Therefore, the balanced equation for the reaction between calcium and fluorine to form calcium fluoride is:

Ca + F2 -> CaF2

A chemical equation is a written representation of a chemical reaction that shows the reactants, products, and their coefficients. The reactants are the substances that are present at the beginning of the reaction, and the products are the substances that are produced as a result of the reaction. The coefficients are the numbers that are placed in front of the reactants and products to indicate the relative amounts of each substance involved in the reaction.

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Answer:

c

Explanation:

Two species of frogs belonging to the same genus occasionally mate, but the embryos stop developing after a day and then die. These two frog species separate by

Answer:

ΔE = 150 J

Explanation:

From first law of thermodynamics, we know that;

ΔE = q + w

Where;

ΔE is change in internal energy

q is total amount of heat energy going in or coming out

w is total amount of work expended or received

From the question, the system receives 575 J of heat. Thus, q = +575 J

Also, we are told that the system delivered 425 J of work. Thus, w = -425 J since work was expended.

Thus;

ΔE = 575 + (-425)

ΔE = 575 - 425

ΔE = 150 J

After applying the first law of thermodynamics, the change in the internal energy of the system is 150 Joules.

Given the following data:

To find the change in the internal energy of the system, we would apply the first law of thermodynamics.​

Mathematically, the first law of thermodynamics is given by the formula:

\(\Delta E = Q - W\)

Where;

Substituting the given parameters into the formula, we have;

\(\Delta E = 575 - 425\)

Change in internal energy, E = 150 Joules

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MgO particles have a mass of 7.4 x 1023 grams.

According to Wikipedia, "a gram molecule can be defined as the amount of a substance equal to its relative molecular mass in grams." One gram of water, for instance, weighs 18 grams (H 2 O = 1 + 1 + 16 = 18 g).

The most common unit used in chemistry to express molarity is the number of moles per liter, represented by the unit sign mol/L or mol/dm3 in SI units. One molar, or 1 M, of a solution's concentration is defined as one mol/L.

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Answer:

0.54 mole of H2O.

Explanation:

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

2CH3OH + 3O2 —> 2CO2 + 4H2O

From the balanced equation above,

2 moles of CH3OH reacted to produce 4 moles of water.

Finally, we shall determine the number of mole of water (H2O) produced by the reaction of 0.27 moles of CH3OH. This can be obtained as follow:

From the balanced equation above,

2 moles of CH3OH reacted to produce 4 moles of water.

Therefore, 0.27 moles of CH3OH will react to produce = (0.27 × 4)/2 = 0.54 mole of H2O.

Thus, 0.54 mole of H2O is produced from the reaction.

Answer:

1.

Chemical: Aspirin

Plant: Willow tree bark

Disease: Used to reduce pain, fever, or inflammation

2.

Chemical: Digoxin

Plant: Flower, Digitalis lanata

Disease: Used to treat various heart conditions

The sample with the largest number of oxygen atoms will be calcium perchlorate.

Since we are not looking at the number of moles, the mass of the compounds has no bearing on the number of atoms of oxygen.

Therefore, the compound with the largest number of oxygen atoms is calcium perchlorate.

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Answer: The acceleration of the ball is 200 m/s².

Explanation:

Force:

Force is the push or pull on an object with mass that causes it to change velocity or to accelerate.

Force represents as a vector, which means it has both magnitude and direction.

Given:

Mass of metal ball = 0.025 kg

Force           = 5 N

To Find:

Acceleration, = ?

Solution:

Formula:

Total, 0.0137 moles of carbon dioxide gas is produced when 2.3 g of sodium bicarbonate decomposes to produce carbon dioxide and sodium hydroxide.

To determine the number of moles of carbon dioxide gas produced, we first need to find the balanced chemical equation for the reaction;

2NaHCO₃ → Na₂CO₃ + CO₂ + H₂O

From this equation, we can see that for every 2 moles of sodium bicarbonate, 1 mole of carbon dioxide is produced.

Next, we need to calculate the number of moles of sodium bicarbonate in 2.3 g using its molar mass;

molar mass of NaHCO₃ = 84.0066 g/mol

moles of NaHCO₃ = mass/molar mass

= 2.3 g / 84.0066 g/mol = 0.0274 mol

Finally, we can use the mole ratio from the balanced equation to find the number of moles of carbon dioxide produced;

moles of CO₂ = (0.0274 mol NaHCO₃) x (1 mol CO₂ / 2 mol NaHCO₃)

= 0.0137 mol CO₂

Therefore, 0.0137 moles of carbon dioxide gas is produced.

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Answer:

65.72 g

Explanation:

mass = density × volume

= 1.02 g/ml × 62 ml

= 65.72 g

2.65g/ml is the density of a piece of granite whose volume is 20 mL and mass is 53grams. Density is the mass of a specific material per unit volume.

Density is the mass of a specific material per unit volume. Density is defined as d = M/V, in which d represents density, M is weight, as well as V is volume. Density is generally expressed in grams every cubic centimetre. Water, for example, has a density of 1 gram per square centimeter, but Earth has a density of 5.51 kilograms per cubic centimetre.

Density is sometimes measured in kilos per cubic centimeter (in metre-kilogram-second or SI units). The density of air, for example, is 1.2 kilos per cubic metre. 

density = mass / volume

            =53/ 20

            =2.65g/ml

Therefore, 2.65g/ml is the density of a piece of granite whose volume is 20 mL and mass is 53grams.

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If the efficiency of a machine increases, it means that the machine is able to convert a higher percentage of its input energy into useful work output.

This could happen due to various factors, such as reducing friction, improving the design of the machine, or using more efficient components. The machine requires less energy input to perform the same amount of work. This could result in cost savings, reduced energy consumption, and lower environmental impact.

The output of the machine increases while the input remains constant. This could result in increased productivity, faster production rates, and improved performance. The wear and tear on the machine may decrease, as it is working more efficiently and experiencing less stress. This could result in longer machine life and reduced maintenance costs. Increasing the efficiency of a machine can have many positive effects, including cost savings, improved performance, and reduced environmental impact.

The complete question is

If the efficiency of a machine increases, what happen?

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Answer:

BONJOUR.

CHEMICAL CHANGE ARE THOSE THAT FORM A NEW SUBSTANCE

PHYSICAL CHANGE ARE THOSE THAT DOESN'T FORM A NEW SUBSTANCE.

OPTION D IS THE ANSWER

I HOPE IT IS HELPFUL.

MERCI

1Al2(SO4)3 + 3ZnCl2 → 2AlCl3 + 3ZnSO4

The coefficients represents moles. There is 1 mole of Aluminum Sulfate, 3 moles of Zinc(II) Chloride, 2 moles of Aluminum Chloride, and 3 moles of Zinc(II) Sulfate.

Now add all the coefficients/moles.

9 is the sum of all the coefficients.

Answer:

Tetrahedral

Explanation:

The molecular geometry of SiCl₄ is a tetrahedral shape. According to the VESPR molecular theory, the compound has a shape of a tetrahedron.

Pressure and volume have an indirectly proportional relationship

Ideal gas laws can help us describe the relationship between different values for gases.

Boyle's Law

The ideal gas law that connects pressure and volume given a constant temperature is Boyle's law. Boyle's law is represented as:

This equation shows that pressure and volume have an indirectly proportional relationship. This means that as pressure increases, volume decreases and vice versa. So, pressure and increase opposite of each other.

Indirect Relationships

Indirect relationships occur when one value and the reciprocal of another are proportional. For example, pressure and 1/volume are directly proportional. This function looks like a decreasing exponential function. Attached is an example of a volume vs. pressure graph.

\(\\ \sf\longmapsto 4x+6=-10\)

\(\\ \sf\longmapsto 4x=-10-6\)

\(\\ \sf\longmapsto 4x=-16\)

\(\\ \sf\longmapsto x=\dfrac{-16}{4}\)

\(\\ \sf\longmapsto x=-4\)

4x + 6 = - 10

4x = -10-6

4x = -16

x = -16/4

× = -4

Answer:

Absolute zero is the theoretical temperature at which all matter would have zero thermal energy and all molecular motion would stop. This temperature is equal to -273.15 degrees Celsius or -459.67 degrees Fahrenheit. It is the lowest possible temperature in the universe and cannot be reached in practice, as it is impossible to completely eliminate all thermal energy from matter.

Answer:

Heat can travel from one place to another in three ways: Conduction, Convection and Radiation. Both conduction and convection require matter to transfer heat. If there is a temperature difference between two systems heat will always find a way to transfer from the higher to lower system.

Explanation:

The time taken or 25% of the molecules to desorb is 2.2 seconds

A first order reaction is one in which the rate of reaction depends on the concentration of a single specie.

Since;

t1/2 = 0.693/k =  0.693/ 0.128 s-1

t1/2 = 5.4 secs

Using the formula;

0.693/t1/2 = 2.303/t log (No/N)

0.693/5.4 = 2.303/t log 1/0.75

0.693/5.4 = 2.303/t log

0.693/5.4 = 0.287/t

t =  2.2 seconds

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The mass of HF produced from the given amounts of BF₃ and H₂ is 99.5 grams.

To solve this problem, we need to use stoichiometry to determine the amount of HF produced from the given amounts of BF₃ and H₂.

From the balanced equation;

2 BF₃ + 3 H₂ → 2 B + 6 HF

We can see that 2 moles of BF₃ react with 3 moles of H₂ to produce 6 moles of HF. This means that the ratio of BF₃ to HF is 2:6, or 1:3.

First, we need to calculate the number of moles of BF₃ and H₂ from their given masses and molar masses;

n(BF₃) = m(BF₃) / M(BF₃) = 40 g / 67.81 g/mol = 0.59 mol

n(H₂) = m(H₂) / M(H₂) = 5 g / 2.02 g/mol = 2.48 mol

Next, we can determine which reactant is limiting by comparing their mole ratios. The ratio of BF₃ to H₂ is 1:1.67, which means there is not enough H₂ to react with all of the BF₃. This makes H₂ the limiting reactant.

To find the number of moles of HF produced, we use the mole ratio from the balanced equation;

n(HF) = n(H₂) × (6 mol HF / 3 mol H₂) = 2.48 mol × 2

= 4.96 mol

Finally, we calculate the mass of HF produced from its number of moles and molar mass;

m(HF) = n(HF) × M(HF) = 4.96 mol × 20.01 g/mol

= 99.5 g

Therefore, the mass of HF is 99.5 grams.

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Answer:

0.067M Fe(NO3)3

Explanation:

A stock solution is a concentrated solution that is diluted to prepare the solutions that you will use.

The volume of the stock solution is 3.0mL + 10.0mL + 17.0mL= 30.0mL.

The ratio between volume of the aliquot (10.0mL) and total volume (30.0mL) is called dilution factor, that is: 30.0mL / 10.0mL = 3

That means the Fe(NO3)3 is diluted 3 times. That means the molar concentration of the stock solution is:

0.200M / 3 =

Answer:

Without rounding significant figures, V = 14.824 mL

With rounding significant figures, V = 10 mL

Explanation:

Based on valence electron trends, the correct answer is C. Group 3A or 13.

Based on trends in valence electrons, the group of pairs with a group 5 non-metal, such as nitrogen (N), in a 1:1 ratio is Group 3A or 13. Group 5 non-metals have 5 valence electrons, and they tend to form compounds by either gaining 3 electrons to achieve a stable octet or by sharing 3 electrons in covalent bonds.

Group 1A or 1 elements, such as hydrogen (H) and lithium (Li), have only 1 valence electron. They would need to gain 4 additional electrons to achieve a stable octet, which is energetically unfavorable.

Group 2A or 2 elements, such as beryllium (Be) and magnesium (Mg), have 2 valence electrons. They would need to gain 3 additional electrons to achieve a stable octet, which is also energetically unfavorable.

Group 6A or 16 elements, such as oxygen (O) and sulfur (S), have 6 valence electrons. They would need to gain only 1 additional electron to achieve a stable octet, making them more likely to form a 2:1 ratio with a group 5 non-metal.

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Within each functional group, the boiling points of members of the group vary according to molecular weight. Therefore, one cannot deduce any functional group from boiling points.

Organic compounds are divided into families called homologous series. Each homologous series has a functional group common to all the members of the series. As a result of this, the chemical properties of all the members of the homologous series are similar.

However, the boiling points of the members of a homologous series vary according the their molecular weights. As such, boiling points can not be used as evidence to classify substances into any particular homologous series.

Summarily, one cannot deduce any functional group from physical properties.

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These substances have dispersed particles that are large enough to scatter light, making the beam visible. Therefore, out of the options provided, a mixture that scatters light is an example of a colloid. Option B)

A colloid is a type of mixture in which particles are dispersed throughout a medium, creating a homogeneous appearance. Unlike solutions, where the particles are completely dissolved, and suspensions, where the particles settle out, colloids have particles that are larger than those in solutions but smaller than those in suspensions. One characteristic of colloids is that they can scatter light due to the size of the particles. This scattering of light is known as the Tyndall effect. Examples of colloids include milk, fog, and aerosol sprays. These substances have dispersed particles that are large enough to scatter light, making the beam visible. Therefore, out of the options provided, a mixture that scatters light is an example of a colloid. Therefore option B) is correct

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Note Complete Question

which is an example of a colloid?

a mixture that settles out,

b mixture that scatters light,

c mixture that is separated by filtration,  

d salt and water mixture?

0.1 mol of sodium hydroxide (NaOH) would react exactly with 7.5 g of the diprotic acid \(H_{2}\)A.

What is Molar Mass?

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is calculated by adding up the atomic masses of all the atoms in a molecule or the formula mass of all the ions in an ionic compound.

The balanced chemical equation for the reaction between diprotic acid, \(H_{2}\)A, and sodium hydroxide, NaOH, can be represented as follows:

2\(H_{2}\)A + 2 NaOH -> \(Na_{2}\)A + 2 \(H_{2}\)O

From the balanced equation, we can see that 2 moles of \(H_{2}\)A react with 2 moles of NaOH to produce 1 mole of \(Na_{2}\)A and 2 moles of water (\(H_{2}\)O).

First, we need to calculate the number of moles of \(H_{2}\)A in 7.5g using the formula:

moles = mass / molar mass

moles of \(H_{2}\)A = 7.5g / 150 g/mol = 0.05 mol

Since diprotic acid, \(H_{2}\)A, reacts in a 1:2 ratio with NaOH, we need to multiply the moles of \(H_{2}\)A by 2 to determine the moles of NaOH required for complete reaction:

Moles of NaOH = 2 * Moles of \(H_{2}\)A

Moles of NaOH = 2 * 0.05 mol

Moles of NaOH = 0.1 mol

0.1 mol of sodium hydroxide (NaOH) would react exactly with 7.5 g of the diprotic acid \(H_{2}\)A.

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