Sodium-24 has a half-life of 14.8 hours. how much of a 227.0 mg sodium-24 sample will remain after 3.7 days?

Final answer:

To find the mass of octane required to produce 6.20 mol CO2, we use the stoichiometry of the combustion reaction and the molar mass of octane, resulting in a requirement of 88.56 grams of octane.

Explanation:

To calculate the mass of octane (C8H18) needed to produce 6.20 mol CO2, we first need the balanced chemical equation for the combustion of octane:

2 C8H18 + 25 O2 → 16 CO2 + 18 H2O

This equation tells us that 2 moles of octane produce 16 moles of CO2. From this, we can find the molar ratio between octane and CO2, which is 2 moles of octane per 16 moles of CO2, or 1 mole of octane for every 8 moles of CO2.

Next, we use the molar mass of octane, which is 114.23 g/mol (C=12.01 g/mol x 8 + H=1.008 g/mol x 18). Given that we have 6.20 moles of CO2, we can calculate the moles of octane needed:

6.20 mol CO2 x (1 mol C8H18 / 8 mol CO2) = 0.775 mol C8H18

Finally, we convert moles of octane to mass:

0.775 mol C8H18 x 114.23 g/mol = 88.56 g C8H18

Therefore, 88.56 grams of octane are needed to produce 6.20 moles of CO2.

By using the Ideal Gas Law and the given conditions, we can calculate the volume of the weather balloon to be approximately 221.4 liters.

The volume of a gas can be determined by using the Ideal Gas Law: PV = nRT. Here, P is the Pressure, V is the Volume, n is the number of moles, R is the universal gas constant and T is the absolute Temperature. The constants provided in the question are the moles of Helium (8.80 moles), the Pressure (0.992 atm) and the Temperature (25 C).

Firstly, we need to convert the temperature from Celsius to Kelvin. The conversion formula is: T(K) = T(C) + 273.15. Thus, T(K) = 25 + 273.15 = 298.15 K.

Now, we use these values in the Ideal Gas Law to find the volume. We rearrange the formula to solve for volume: V = nRT / P. Substituting the given values and the gas constant R as 0.0821 atm L/mol K, we get:

V = (8.80 moles * 0.0821 L atm / (mol K) * 298.15 K) / 0.992 atm = 221.4 L

Therefore, the volume of the weather balloon under the given conditions is approximately 221.4 Liters.

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Final answer:

To find the molality of a KBr solution, divide the mass of KBr (2.10 g) by its molar mass (119.0 g/mole) to get moles, and then divide by the mass of the solvent in kilograms (0.897 kg of water).

Explanation:

The concentration of KBr in a solution prepared by dissolving 2.10 g of KBr in 897 g of water is calculated using the molality formula. Molality is defined as the number of moles of solute per kilogram of solvent. First, we need to find the number of moles of KBr by dividing the mass (2.10 g) by its molar mass (119.0 g/mole), which gives us the number of moles. Then, we divide the number of moles by the mass of the solvent (water) in kilograms to obtain the molality of the solution.

The calculation is as follows:

By performing these calculations, we can determine the molality of the KBr solution.

Answer: The net ionic equation is written below.

Explanation:

Net ionic equation of any reaction does not include any spectator ions.

Spectator ions are defined as the ions which does not get involved in a chemical equation. They are found on both the sides of the chemical reaction when it is present in ionic form.

The chemical equation for the reaction of iron (II) chloride and potassium hydroxide is given as:

[tex]FeCl_2(aq.)+2KOH(aq.)\rightarrow Fe(OH)_2(s)+2KCl(aq.)[/tex]

Ionic form of the above equation follows:

[tex]Fe^{2+}(aq.)+2Cl^-(aq.)+2K^+(aq.)+2OH^-(aq.)\rightarrow Fe(OH)_2(s)+2K^+(aq.)+2OH^-(aq.)[/tex]

As, potassium and hydroxide ions are present on both the sides of the reaction. Thus, it will not be present in the net ionic equation and are spectator ions.

The net ionic equation for the above reaction follows:

[tex]Fe^{2+}(aq.)+2OH^-(aq.)\rightarrow Fe(OH)_2(s)[/tex]

Hence, the net ionic equation is written above.

Iron(II) chloride reacts with potassium hydroxide to form iron(II) hydroxide and potassium chloride. The net ionic equation, which only includes the particles that participate in the reaction, is: Fe2+(aq) + 2 OH-(aq) → Fe(OH)2(s). Potassium and chloride ions are spectator ions and aren't included.

The reaction between iron(II) chloride (FeCl2) and potassium hydroxide (KOH) produces iron(II) hydroxide (Fe(OH)2) and potassium chloride (KCl). The balanced chemical equation for this reaction is:

FeCl2(aq) + 2 KOH(aq) → Fe(OH)2(s) + 2 KCl(aq).

The net ionic equation only includes the ions and molecules directly involved in the reaction, which are Fe2+, Cl-, K+, and OH-. Therefore, the net ionic equation will look like this:

Fe2+(aq) + 2 OH-(aq) → Fe(OH)2(s).

The potassium ions (K+) and chloride ions (Cl-) do not participate directly in the reaction so they are not included. They are known as the spectator ions.

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Final answer:

C4H8 is the formula that represents an organic compound among the given options because it contains both carbon and hydrogen atoms.

Explanation:

To determine which formula represents an organic compound, we must identify a compound containing carbon (C) with some hydrogen (H). Typically, organic compounds have carbon-hydrogen bonds and often contain other elements like oxygen, nitrogen, sulfur, and phosphorus.

Looking at the options provided:

CAH2 - Calcium hydride, an inorganic compound.

C4H8 - This is a hydrocarbon with four carbon atoms and eight hydrogen atoms, which is characteristic of an organic compound.

H2O2 - Hydrogen peroxide, an inorganic compound.

P2O5 - Diphosphorus pentoxide, an inorganic compound.

Therefore, C4H8 is the formula that represents an organic compound, as it consists of carbon and hydrogen atoms, meeting the criteria for organic chemistry.

Answer:

infared detectors

Explanation:

Ionic compounds are brittle because due to the strong bond between the positive and negative ions that formed the molecules. These positive and negative bonds produce crystals in rigid, lattice structures.

The term ionic compound is defined as the compounds made up of ions that produce charged particles when an atom or group of atoms gains or loses electrons.

Because of their electrostatic attractions, ionic compounds are brittle. These forces keep anions and cations in specific positions in a crystal lattice. Metals, on the other hand, are malleable because the atoms can roll over and create new positions, thereby maintaining their bonds.

Thus, ionic compounds are brittle.

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The mass of  potassium chloride formed is 31.5 g

The number of moles of chlorine gas  is obtained from the ideal gas equation;

P = 0.943 atm

V = 5.11 l

T = 286 K

n = ?

R = 0.082 atm L K-1mol-1

From;

PV = nRT

n = PV/RT

n =  0.943 atm * 5.11 l/0.082 atm L K-1mol-1 * 286 K

n =4.819 /23.452

n = 0.21 moles of Cl2

Number of moles of K = mass/molar mass = 29.0 g/39 g/mol = 0.74 moles

Equation of the reaction is;

2K + Cl2 ----> 2KCl

Since the reaction is 2:1

1 mole of Cl2 reacts with 2 moles of K

0.21 moles of Cl2 reacts with 0.21 * 2/1 = 0.42 moles of K

This means that K is the reactant in excess.

1 mole of Cl2 yields 2 moles of KCl

0.21 moles of Cl2 yields  0.21 * 2/1 = 0.42 moles of KCl

Molar mass of KCl = 75 g/mol

Mass of KCl = 0.42 moles of KCl * 75 g/mol

Mass of KCl = 31.5 g of KCl

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Approximately 32.77 liters of gas will be produced by the decomposition of 32.0 g of NH4NO2 at 525°c and 1.5 atm.

Decomposition of 32.0g of NH₄NO₂ can be calculated by using the Ideal Gas Law PV=nRT where P is the pressure, V is the volume, n number of moles, R the gas constant and T temperature. Given the molar mass of  NH₄NO₂ is about 64.04 g/mol, we divide 32.0g by 64.04 g/mol to get 0.5 moles of NH₄NO₂  The reaction of NH₄NO₂ decomposing to N₂ and H₂O shows that for every 1 mole of NH₄NO₂ , 1 mole of N₂ and 2 moles of H2O are produced. Thus, in total, by decomposing 0.5 moles of  NH₄NO₂  we produce 0.5 * 3 = 1.5 moles of gases at 525 °C and 1.5 atm.

Applying these values into the Ideal Gas Law, substituting R for the value of 0.0821 (when pressure is in atm, volume in L, and T in kelvin), and noting that 525°C is equivalent to 798.15 K (273.15 + 525 = 798.15), we get V = (1.5*0.0821*798.15)/1.5. By solving this, we get the volume of gasses to be approximately 32.77 liters.

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The volcanic eruption warning sign has not been the widening of the surface and cracks in the volcano. Thus, option 2 is correct.

Volcanic eruptions can be defined as the coming out of the lava and the magma from the earth's crust. The volcanic eruptions have consisted of magma along with several gases.

The change in the chemistry of the volcanic gas has been the warning sign of the eruption as there has been a change in the pressure and temperature of the gases that results in the explosion.

The volcanic eruption has been mediated by the shift in the earth's crust leading to earthquake activity.

The volcanic eruption has also been mediated with the warning sign as the activity of the animals, as some animals have been capable of listening to the waves that have been the indication of the volcanic eruption.

In the volcanic eruption, there has been no widening of the earth's surfaces or cracks in the volcano. However, this has been an alarming sign of the movement of the tectonic plate. Thus, option 2 is correct.

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The activity of animals is not a scientific indicator for predicting volcanic eruptions, unlike seismic activity, gas emissions, and geological changes.

The question asks which of the following is NOT a warning sign used to predict a volcanic eruption. Changing chemistry of volcanic gas, development and widening of surface cracks on the volcano, and earthquake activity are all regarded as warning signs of a potential volcanic eruption. However, the activity of animals is not considered a reliable scientific indicator for predicting volcanic eruptions. Animal behavior can be influenced by many factors, and while there are anecdotal reports of animals acting unusually before an eruption, it is not used as a primary method of prediction by volcanologists. Instead, they rely on more measurable signs like seismic activity, gas emissions, and geological changes.

Ethyl acetate is a solvent used in varnishes and nail polish remover, and it is produced by heating acetic acid and ethanol in the presence of sulfuric acid. It is also used to extract caffeine from coffee and to remove nail polish and paint.

Ethyl acetate is a sweet-smelling solvent used in varnishes and fingernail polish remover. It is produced industrially by heating acetic acid and ethanol together in the presence of sulfuric acid, which is added to speed up the reaction. The ethyl acetate is distilled off as it is formed.

Ethyl acetate (CH, CO₂C₂H5) is the solvent in many fingernail polish removers and is used to decaffeinate coffee beans and tea leaves. It is prepared by reacting ethanol (C₂H5OH) with acetic acid (CH₂CO₂H); the other product is water. A small amount of sulfuric acid is used to accelerate the reaction, but the sulfuric acid is not consumed and does not appear in the balanced chemical equation.

Esters are common solvents. Ethyl acetate is used to extract organic solutes from aqueous solutions-for example, to remove caffeine from coffee. It also is used to remove nail polish and paint.

Final answer:

The Mediterranean Sea is the body of water between 30°N and 40°N latitude of Africa, bordering countries such as Egypt, Libya, and Tunisia.

Explanation:

The body of water located between 30°N and 40°N latitude of Africa is the Mediterranean Sea. This sea is situated to the north of the African continent and it borders several African countries including Egypt, Libya, and Tunisia within the specified latitudinal range. To its north are southern European countries, and to the east, it connects with the Middle East. The Nile River, one of the longest rivers in the world, empties into the Mediterranean Sea after flowing north through Egypt.

The left side of the equation HBr(aq) + 2NaOH(aq) includes a total of three hydrogen (H) atoms, one bromine (Br) atom, two sodium (Na) atoms, and two oxygen (O) atoms.

To list the number of each type of atom on the left side of the chemical equation [tex]HBr(aq) + 2NaOH(aq) \rightarrow 2NaBr(s) + H_2O(l)[/tex], we first need to identify each atom present in the reactants. For HBr, we have one hydrogen (H) atom and one bromine (Br) atom. Then, for 2NaOH, since it has a coefficient of two, we count two sodium (Na) atoms, two oxygen (O) atoms, and two hydrogen (H) atoms. Therefore, the total count of each type of atom on the left side is:

To find the pH after adding 14.0 mL of 0.25 M KOH to 50.0 mL of 0.15 M HBr, calculate the excess HBr and then use its concentration to determine the pH, assuming HBr dissociates completely as it's a strong acid.

To calculate the pH after the addition of 14.0 mL of 0.25 M KOH to 50.0 mL of 0.15 M HBr, we first need to determine if the reaction has reached the equivalence point. The millimoles of HBr initially present are calculated by multiplying the volume in liters by the molarity: 50.0 mL x 0.15 M = 7.5 mmol. Then, calculate the millimoles of KOH added: 14.0 mL x 0.25 M = 3.5 mmol.

Since we have more HBr than KOH, HBr is in excess and KOH is the limiting reactant. The excess amount of HBr is 7.5 mmol - 3.5 mmol = 4.0 mmol. The pH is determined by the concentration of the remaining HBr. To find this concentration, we take the remaining mmol of acid and divide by the total volume of the solution in liters (original acid solution plus the volume of KOH added).

The total volume after the addition of KOH is 50.0 mL + 14.0 mL = 64.0 mL or 0.064 L. The concentration of HBr is 4.0 mmol / 0.064 L. Now, convert mmol to mol by dividing by 1000, resulting in 4.0 x 10-3 mol / 0.064 L. Since HBr is a strong acid, it dissociates completely in water. The pH can be calculated using the formula pH = -log[H+], where [H+] is the concentration of hydronium ions, which is equal to the concentration of HBr.

Therefore, the pH is -log(4.0 x 10-3 / 0.064 L). Calculate this value to get the pH of the solution after the addition of 14.0 mL of KOH.

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Final answer:

Malonic ester synthesis converts alkyl halides to carboxylic acids with two additional carbons.

Explanation:

Malonic ester synthesis involves a series of reactions converting an alkyl halide into a carboxylic acid with two additional carbons. The final product after treating malonic ester successively with sodium ethoxide, ethyl bromide, potassium tert-butoxide, isobutyl chloride, hot aqueous sodium hydroxide, hydrochloric acid, and heat would be a carboxylic acid with a methyl group attached.

Answer:

48.83

Explanation:

on edge

Water has a neutral pH of 7 on the pH scale, while hydrochloric acid is a strong acid with a pH of around 1 to 2, indicating a much higher level of acidity than water.

On the pH scale, water and hydrochloric acid (HCl) lie at different points reflecting their levels of acidity. Water is neutral with a pH of 7, serving as the midpoint of the pH scale.

In contrast, hydrochloric acid is a strong acid with a pH significantly lower than 7; typically around 1 to 2 due to its high concentration of hydronium ions. The lower the pH value, the more acidic the substance is. Hence, hydrochloric acid has a much higher acidity than water.

The molecular formula for a compound with 64.27% carbon, 7.19% hydrogen, and 28.54% oxygen with a molar mass of 168.19 g/mol is C9H12O3.

First, we assume 100g of the compound is present so the percentages can be taken as the mass in grams of each element. This gives us 64.27g of carbon, 7.19g of hydrogen, and 28.54g of oxygen. Then, we convert grams to moles using each element's molar mass (C=12.01g, H=1.01g, and O=16.00g).

So, for Carbon we get:

64.27g/12.01g = 5.349 moles

For Hydrogen we get:

7.19g/1.01g = 7.119 moles

For Oxygen we get:

28.54g/16.00g = 1.784 moles.

Now, we divide each mole number by the smallest number of moles calculated in the previous step (1.784) to determine the mole ratio, rounding to the nearest whole number. This will give us C3H4O1. Thus, our empirical formula (the formula in its lowest terms) is C3H4O1.

The next step is to determine the molecular formula, which tells us the actual number of atoms of each element in a molecule of the compound. To find the molecular formula, we compare the empirical formula mass to the molar mass of the compound to find a multiple which we then use to multiply the subscripts in our empirical formula. Therefore, with a molar mass of 168.19 g/mol and an empirical formula weight of 56.06 g/mol (C3H4O1), we find our multiple to be 3 (around 168/56).

The resulting molecular formula would be C9H12O3, meaning our compound consists of 9 carbon atoms, 12 hydrogen atoms, and 3 oxygen atoms.

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