Helen goes to the doctor and has a thyroid test done. She receives 20 grams of radioactive iodine. After 8 hours, 10 grams of the iodine have broken down. After 16 hours, there are 5 grams of iodine left.
What is the half-life of the radioactive iodine?
8 hours

Answer:

i think iron

Explanation:

i not sure with my ans

Answer:

Explanation:

You can make a couple of statements.

Answer:

The wolves role in the ecosystem is to hunt/eat deer. In the question it states, "...ranchers aggressively killed wolves because they posed a threat to their cattle. As the wolf population declined, the deer population began increasing." It's clearly cause and affect, the wolves use to eat a lot of deer, then a large percentage of wolves died by the ranchers. The wolves role in the ecosystem is to hunt deer and help balance out animal to vegetation ratio.

Explanation:

Because i'm awesome lol

(Give me good ratings pleaseeeee.

The factors that affect the rate of solution formation are capable of either increasing the rate of solution formation or decreasing it.

The rate of solution formation from a chemical reaction depends on the following factors:

Therefore, the factors that affect the rate of solution formation are capable of either increasing the rate of solution formation or decreasing it.

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It would take approximately 15,000 minutes (rounded to the nearest whole number) for the dripping faucet to fill a 1.00-gallon bucket. we can use the given information about the rate of water dripping from the faucet.

Given:

- Rate of water dripping = 41 drops/minute

- Number of drops in a gallon = 15,000 drops

We need to convert the number of drops into gallons and then determine the time required.

1 gallon = 15,000 drops

Let's set up the conversion:

(1.00 gallon / 15,000 drops) × (41 drops / 1 minute) = (1.00 gallon × 1 minute) / (15,000 drops)

Simplifying the equation:

(1.00 gallon × 1 minute) / (15,000 drops) = 0.0000666667 gallon/minute

Now, we can calculate the time required to fill a 1.00-gallon bucket:

Time = Volume / Rate

Time = 1.00 gallon / (0.0000666667 gallon/minute)

Calculating the result:

Time = 1.00 gallon / (0.0000666667 gallon/minute) = 15,000 minutes

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The largest effect on the population of trout in Wisconsin was caused by the introduction of non-native species into the ecosystem.

The introduction of non-native species into an ecosystem can cause a disruption in the food chain, leading to a decrease in the population of native species. In Wisconsin, the introduction of non-native species such as the brown trout and rainbow trout has had a significant impact on the population of native brook trout.

The non-native species compete with the native brook trout for food and habitat, which has led to a decrease in the brook trout population. This highlights the importance of preserving the natural balance of ecosystems and avoiding the introduction of non-native species.

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Answer:

protons: positively charged, located in the nucleus

electrons: negatively charged, located outside the nucleus

neutrons: no charge, located in the nucleus

The relationship between the rate of diffusion r, and d is r ∝ 1/√d.

The relationship between the rate of diffusion (r) and the density of a gas (d) can be explained using Graham's law of diffusion. According to this law, the rate of diffusion of a gas is inversely proportional to the square root of its density. Mathematically, it can be expressed as:

r ∝ 1/√d

where the symbol '∝' represents 'proportional to'. The constant of proportionality (k) can be introduced to this equation as:

r = k/√d

This equation shows that as the density of a gas increases, its rate of diffusion decreases. This is because denser gases have more molecules per unit volume and thus, they experience greater intermolecular collisions that hinder their movement. Therefore, it requires more energy for them to diffuse through a medium compared to less dense gases.

The relationship between the rate of diffusion and density is particularly important in understanding the behavior of gases in different environments. For instance, in a gas chromatography column, the rate of diffusion of a gas determines how quickly it moves through the column and separates from other components. Similarly, in the Earth's atmosphere, the rate of diffusion of greenhouse gases such as carbon dioxide affects their concentration and hence, their impact on climate change.

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Explanation:

To calculate the pressure of our oxygen gas sample we will have to use the ideal gas law.

P * V = n * R * T

P = n * R * T/V

If we use the ideal gas constant R in atm*L/(mol*K), P will be the pressure in atm, n the number of moles, T the temperature in K and V the volume in L.

R = 0.082 atm*L/(mol*K)

So we will have to convert the volume in mL to L, the temperature in °C to K and the mass into moles.

T = (273.15 + 12) K

T = 285.15 K

1000 mL = 1 L

V = 140 mL * 1 L/(1000 mL)

V = 0.140 L

To convert the mass into moles we will have to convert from µg to grams and then from grams to moles using the molar mass of O₂.

1 g = 1 *10^6 µg

mass of O₂ = 2.1 µg * 1 g/( 1 *10^6 µg)

mass of O₂ = 2.1 * 10^(-6) g

atomic mass of O = 16.00 amu

molar mass of O₂ = 2 * 16.00 g/mol

molar mass of O₂ = 32.00 g/mol

moles of O₂ = 2.1 *10^(-6) g * 1 mol/(32 g)

moles of O₂ = 6.56 * 10^(-8) moles

n = 6.56 * 10^(-8) moles

Now that we know the different values we can replace them in the ideal gas formula and solve it for P.

P = n * R * T/V

P = 6.56 * 10^(-8) mol * 0.082 atm*L/(mol*K)* 285.15 K/(0.140 L)

P = 1.10 *10^(-5) atm

The pressure is 1.10 *10^(-5) atm but we need it in torr, so to answer our problem we have to convert the pressure from atm to torr.

760 torr = 1 atm

P = 1.10 *10^(-5) atm * 760 torr/(1 atm)

P = 0.00836 torr

Answer: the pressure is 0.00836 torr.

Answer:

cover A

Explanation:

Answer:

cover sorry if im wrong

Explanation:

the cover makes the kiete float using air resisance

Answer:

a . eight tenths of her cookies

Explanation:

Let the total number of Lakesha's cookies be represented by x.

So that;

She gave three tenths to Bailey = \(\frac{3}{10}\) of x

                                                     = \(\frac{3x}{10}\)

She gave five tenths to Helen = \(\frac{5}{10}\) of x

                                                  = \(\frac{5x}{10}\)

Fraction of Lakesha's cookies given away = \(\frac{3x}{10}\) + \(\frac{5x}{10}\)

                                                      = \(\frac{3x+ 5x}{10}\)

                                                      = \(\frac{8x}{10}\)

Thus, the fraction of cookies given away by Lakesha is \(\frac{8}{10}\).

Answer:

1. CuO, 2. O2, and 3. Cu2O.

Explanation:

You can identify that we can state a synthesis reaction between Cu2O and O2 to form CuO:

The reactants are Cu2O and O2, and the product is CuO.

The answer would be 1. CuO, 2. O2, and 3. Cu2O.

Answer:

Copper (Cu), chemical element, a reddish, extremely ductile metal of Group 11 (Ib) of the periodic table that is an unusually good conductor of electricity and heat. Copper is found in the free metallic state in nature.

Explanation:

hope this helps:)

Answer:

4 covalent bonds

Explanation:

Each carbon atom can form as many as four covalent bonds with other carbon atoms as well as with other elements. Be able to explain why this is so. Be able to list the four main groups of organic molecules and their functions in living things.

The mass percentage of each element in baking soda is:

The calculation of mass percentage for each element is as follows:

In this way, the mass percentage should be calculated by dividing each one from the baking soda sample.

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Answer:

The mass percentages of sodium, hydrogen, carbon, and oxygen are 27.37%, 1.20%, 14.30%, and 57%, respectively.

Explanation:

The mass percentage (%mass) of an element present in a compound is calculated using the following expression:

\(\rm \%mass=\dfrac{mass\;of\;the\;element}{mass\;of\;the\;compound}\times 100\%\)

According to the given problem, the mass of \(\rm NaHCO_3\) is 168.02 g.

The mass of sodium in the given sample is 45.98 g.

So, the %mass of sodium in the given sample is calculated as shown below:

\(\rm \%mass\;of\;sodium=\dfrac{45.98\;g}{168.02\;g}\times 100\%=27.37\%\)

Similarly, the mass percentages of hydrogen, carbon, and oxygen are calculated as shown below:

\(\rm \%mass\;of\;hydrogen=\dfrac{2.02\;g}{168.02\;g}\times 100\%=1.20\%\)

\(\rm \%mass\;of\;carbon=\dfrac{24.02\;g}{168.02\;g}\times 100\%=14.30\%\)

\(\rm \%mass\;of\;oxygen=\dfrac{96\;g}{168.02\;g}\times 100\%=57\%\)

Hence, the mass percentages of sodium, hydrogen, carbon, and oxygen are 27.37%, 1.20%, 14.30%, and 57%, respectively.

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Answer:

option d is right

Explanation:

More precipitation occurs near the equator because it is a tropical area. Mountains receive less than 15 inches of rain per year while the equator area receives a lot of rain. This is due to the very hot weather.

The climate around the equator will have more precipitation because it is very hot.

thats the answer

Answer:

Explanation:

% yield = (actual yield / theoretical yield) X 100

For this question,

% yield = (150g/ 162 g) X 100 = 92.6%

Answer:

92.6%

Explanation:

A solution has a pH of 5.4, the determination of [H+].

Take negative to other side

-pH = log H+

multiple Antilog on both side

(Antilog and log cancel each other )

Antilog (-pH) = [ H+ ]

New Formula :- Antilog (-pH) = [+H]

Now put the values of pH in new formula

Antilog (-5.4) = [+H]

we can write -5.4 as (-6+0.6) just to solve Antilog

Antilog ( -6+0.6 ) = [+H]

Antilog (-6) × Antilog (0.6) = [+H]

\(Antilog (-6) = {10}^{ - 6} , \\ Antilog (0.6) = 4 \)

put the value in equation

\( {10}^{ - 6} \times 4 = [H+] \\ 4 \times {10}^{ - 6} = [H+]\)

The final temperature (in °C) when 25.0 mL of 5.42 M HCl are mixed with 25.0 mL of 4.32 M NaOH, if each solution starts at 25.0 °C is 28 °C.

The reaction is given as :

HCl  +  NaOH  ----->    H₂O   +   NaCl

moles of HCl = 5.42 × 0.025

                      = 0.135 mol

moles of NaOH = 4.32 × 0.025

                          = 0.108 mol

moles of reaction = 0.108 mol

specific heat capacity is given as:

Q = mc ΔT

Q = 0.108 × (- 55.8) = - 6.026 kJ = 602.6 J

total volume = 25 ml + 25 ml = 50 ml

mass = density × volume

         = 1.04 × 50 = 52 g

now, Q = mc ΔT

          602.6  = 52 × 3.93 × ( T - 25)

The final temperature T = 28 °C

Thus, The final temperature (in °C) when 25.0 mL of 5.42 M HCl are mixed with 25.0 mL of 4.32 M NaOH, if each solution starts at 25.0 °C is 28 °C.

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a) The balanced chemical equation for the reaction is: 2H₂ + O₂ → 2H₂O

b) the number of moles of O₂ required is approximately 1.004 moles.

c)  approximately 45 liters of H₂ and 22.5 liters of O₂ are needed to obtain 45 liters of H₂O.

a) Balancing the chemical equation:

The balanced chemical equation for the reaction is: 2H₂ + O₂ → 2H₂O

b) Calculating the number of moles of the reactants needed to obtain 45 liters of H₂O:

From the balanced equation, we can see that for every 2 moles of H₂O produced, we need 2 moles of H₂ and 1 mole of O₂. Since the stoichiometry is based on moles, we need to convert the given volume of H2O into moles.

To convert volume to moles, we need to use the ideal gas law, PV = nRT. At standard temperature and pressure (STP), the molar volume of an ideal gas is 22.4 liters.

Given that we have 45 liters of H2O, we can calculate the number of moles as follows:

moles of H₂O = (volume of H₂O) / (molar volume at STP)

            = 45 liters / 22.4 liters/mol

            ≈ 2.008 moles of H₂O

Since the stoichiometry of the reaction is 2 moles of H₂O for every 2 moles of H₂, we need an equal number of moles of H₂. Therefore, the number of moles of H₂ required is also approximately 2.008 moles.

For O₂, since the stoichiometry is 1 mole of O₂ for every 2 moles of H₂O, we need half the number of moles of H₂O. Thus, the number of moles of O₂required is approximately 1.004 moles.

c)  the volume of the reactants:

Since the stoichiometry of the balanced equation is 2 moles of H₂for every 1 mole of O₂ and 2 moles of H₂O, we can deduce the volume of the reactants based on their molar volumes at STP.

For 2.008 moles of H₂, the volume can be calculated as follows:

volume of H₂= (moles of H₂) * (molar volume at STP)

            = 2.008 moles * 22.4 liters/mol

            ≈ 45 liters of H₂

For 1.004 moles of O₂, the volume can be calculated similarly:

volume of O₂= (moles of O₂) * (molar volume at STP)

            = 1.004 moles * 22.4 liters/mol

            ≈ 22.5 liters of O₂

Therefore, approximately 45 liters of H₂and 22.5 liters of O₂ are needed to obtain 45 liters of H₂O

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Freshly-cut eggplant, while uncovered to the air, quickly oxidizes and turns black, kind of the manner an apple goes brown after it is reduced and uncovered to air. the Apple inexperienced eggplant's outer skin is smooth, shiny, and maybe yellow or pale inexperienced.

Leaving slices of apples exposed to the air results in the apple turning an acquainted brown shade. This process, referred to as enzymatic browning, is due to the reaction of positive enzymes with phenolic compounds, both gift inside the apple, that occurs when they may be uncovered to oxygen inside the air.

The eggplant turns brown whilst uncovered to air because a reaction is occurring whilst a cut piece of fruit is exposed to oxygen. this is called enzymatic browning. The call enzymatic browning comes from the truth that an enzyme positioned inside the fruit reacts with oxygen from the air to turn the fruit brown.

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A - That can't be the correct one because the math does not fit the whole reaction, if we have 10g of solid + 10g of liquid and 13g of the final solution, we can't have 5g of gas, otherwise we would have 2g missing and according to the Law of Conservation of Mass, whatever comes in as reactant must come out as product;

B - Again, we don't have "matter being destroyed", that does not happen with chemical reactions, and that is the basis for stoichiometry;

C - Correct answer, 13g of solution + 7g of gas = 20g, exactly the sum of liquid and solid;

D - That would make to final sum be 26g, which is more than the sum of the mass of the reactants

Answer:

1. ELECTRON MOVES FROM THE n = 4 to n = 1 LEVEL

2. ENERGY IS EMITTED

3. THE ELECTRON MOVES CLOSER TO THE NUCLEUS

Explanation:

the question is incomplete as the picture is not shown but here is the picture and the solution.

Bohr model of the hydrogen atom shows that electrons would not emit energy but emit or absorb protons as it moves to a lower or higher energy levels respectively. In this question as shown in the picture below, the hydrogen atom moves from energy level 4 to energy level 1 and in such transition, energy is emitted and returns to its ground state after been excited to a higher level o n equals to 4. The energy emitted follows the law of conservation of energy. That is the amount of energy needed to excite the atom to a higher level is emitted upon transition back to the ground state.

The size of the hydrogen atom will also reduce and the electron will move closer to the nucleus. This is because as energy increases, the electron is found at a greater distance away from the nucleus and vice versa. And as the electron moves farther away the electrostatic force between it and the nucleus reduces and it is loosely held by the nucleus and vice versa, As the case of the question, the electron moves closer to the nucleus and it is strongly attached to the nucleus due to increase electrostatic attraction between it and the nucleus.

Answer:

In this transition, energy is emitted

The electron moves closer to the nucleus

Explanation:

In the Bohr's model of the atom, electrons occupy specific energy levels shown by the principal quantum number. An electron that is stationary in its orbit does not radiate energy.

However, an electron may absorb energy and be excited to higher energy levels or emit energy when descending from a higher to a lower energy level. This energy is usually observed as a photon of light of appropriate wavelength and frequency.

In the image, the electron descends from energy level n=4 to energy level n=1. Since it has moved from a higher to a lower energy level, energy is emitted. Recall that energy levels increase outwards from the nucleus. Since n=1 is closest to the nucleus, the electron has moved closer to the nucleus. Hence the answers above.

The amount of dry solute it would take to prepare 118 mL of 0.105 M NaNO3 is 1.05g.

The mass of a substance can be calculated by multiplying the number of moles in the substance by its molar mass as follows:

mass = no of moles × molar mass

However, the number of moles it took to prepare 118 mL of 0.105 M NaNO3 must be calculated as follows;

no of moles = 0.105 × 0.118 = 0.0124 moles

molar mass of sodium nitrate = 85g/mol

mass = 85g/mol × 0.0124 moles = 1.05g

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The SI unit to the quantity it measures are:

Mass: The mass of an object is a measure of its amount of matter. The SI unit of mass is the kilogram (kg) or gram (g).

Temperature: Temperature is a measure of the average kinetic energy of the particles in a substance. The SI unit of temperature is the kelvin (K).

Time: Time is a measure of the interval between two events. The SI unit of time is the second (s).

Electric current: Electric current is a measure of the flow of electric charge. The SI unit of electric current is the ampere (A).

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Complete question:

Drag the tiles to the correct boxes to complete the pairs. Not all tiles will be used.

Match each SI unit to the quantity it measures.

Answer: About 0.20 grams of copper (II) is formed, and some aluminum is left in the reaction mixture

Answer:Answer B: About 0.20 grams of copper (II) is formed, and some aluminum is left in the reaction mixture

Explanation:

Answer:

Independent Variable: Number of Coils Wrapped Around

Dependent Variable: Number of Paperclips Magnet Picks Up

Possible Research Question: How does the number of wire wraps affect the strength of an electromagnet?

Trends noticed in the data: As the number of wire wraps (coils) around the nail increases, the magnetic strength of the electromagnet also increases. There is a positive correlation between the number of wire wraps and the number of paper clips the magnet picks up.

Claim based on the data: The magnetic strength of an electromagnet increases as the number of wire wraps (coils) around the nail increases.

Evidence from the chart or graph supporting the claim: The graph shows that as the number of wire wraps increases from 4 to 12, the number of paper clips the magnet picks up also increases from 6 to 25. This suggests a positive correlation between the two variables.

In the graph we see that when we increase the mass of baking soda, the volume of CO2 formed increases. Since there will be more reagent to react.

But there comes a mass when the slope flattens out and presents a similar volume even if the mass of baking soda is increased.

This may be because the other reactant becomes a limiting reactant, so the gas production will no longer depend on the amount of mass of baking soda but on the other reactant. That is why you see two slopes with different behaviors.

Answer:

fishery

An area with a large population of valuable ocean organisms is called a fishery. If it was correct mark me as brainiest