A 250-mg sample of carbon from wood underwent 15300 carbon-14 disintegrations in 36 hours. Estimate the time since the death of the sample.

Answer:

Every atom of a given element has the same number of protons

The protons in the nucleus of the helium atom are held together by a force called the strong nuclear force.

Explanation:

Atoms are composed of electrons, protons and neutrons. The electron is negatively charged, protons are positively charged and the neutrons have no charge.

Electrons are found in shells while protons are found inside the atomic nucleus. Similar to electrostatic forces between electron and proton, protons of helium are held together by a strong nuclear blinding force.

Note that, all isotopes must have the same atomic number. This shows that they are all the same atom changed by differences in number of neutrons.

Answer:

[tex]C_9H_8O_4+C_2H_3O_2^-\rightarrow C_2H_4O_2+C_9H_7O_4^-[/tex]

Explanation:

Hello there!

In this case, according to the given information, it turns out possible for us to figure out the required net ionic equation by firstly writing out the complete molecular equation between aspirin and sodium acetate:

[tex]C_9H_8O_4+NaC_2H_3O_2\rightarrow C_2H_4O_2+NaC_9H_7O_4[/tex]

Whereas acetic acid and sodium acetylsalicylate are formed. Now, we write the complete ionic equation whereby sodium acetate and sodium acetylsalicylate are ionized because they are salts yet neither aspirin nor acetic acid are ionized as they are weak acids:

[tex]C_9H_8O_4+Na^++C_2H_3O_2^-\rightarrow C_2H_4O_2+Na^++C_9H_7O_4^-[/tex]

Finally, for the net ionic equation we cancel out the sodium spectator ions to obtain:

[tex]C_9H_8O_4+C_2H_3O_2^-\rightarrow C_2H_4O_2+C_9H_7O_4^-[/tex]

Regards!

Answer:

B

Explanation:

Answer:

i. HCIO2 - 2.9

ii. CH3COOH - 2.64

iii. HF - 3.27

iv. HNO2 - 2.67

Explanation:

The Ph value differ for base and acid. A neutral solution will have Ph value of 7. For acid the Ph value is less than 7 and for base Ph value is greater than 7. The highest Ph value for the given acids is 3.27 for hydroflouric acids.

The pH of the resulting solution is 3.16. Acetic acid having the formula [tex]CH_3COOH[/tex] would produce the highest pH at the equivalence point in a weak acid-strong base titration.

Kingsley adds 49.28 mL of NaOH to 250.00 mL of the HCOOH solution.

The neutralization reaction resulted in 0.098 moles of HCOOH and 0.025 moles of HCOO⁻ left in the solution.

We have to determine the pH of the resulting solution and identify the acid that would produce the highest pH at the equivalence point in a weak acid-strong base titration.

pH, a quantitative measure of the acidity or basicity of aqueous or other liquid solutions.

Kingsley adds 49.28 mL of NaOH to 250.00 mL of the HCOOH solution.

Total volume of the solution = 49.28 mL + 250.0 mL = 299.28 mL = 0.29928 L

At neutralization point, HCOOH = 0.098 mol = [tex]\frac{0.098\ mol}{0.29928\ L} = 0.32745\ M[/tex]

So, Concentration of HCOOH at neutralization point = 0.32745 M

And [tex]HCOO^-[/tex] at neutralization point = 0.025 mol = [tex]\frac{0.025\ mol}{0.29928\ L} = 0.08353\ M[/tex]

So, Concentration of HCOO⁻ at neutralization point = 0.08353 M

Now, [tex]K_a[/tex] value of HCOOH = [tex]1.77\times10^{-4}[/tex] (reference value}

We know that [tex]pK_a = -logK_a[/tex]

[tex]pK_a = -log(1.77\times10^{-4}) = 3.75[/tex]

Now, HCOOH  is acid and HCOO⁻ is the conjugate base.

According to Henderson Hasselblach equation:

[tex]pH = pK_a + log\frac{[conjugate\ base]}{[acid]}\\ \therefore pH = 3.75 + log\frac{[HCOO^-]}{[HCOOH]}\\pH = 3.75 + log(\frac{0.08353}{0.32745})\\pH = 3.75 +(-0.59)\\pH = 3.16[/tex]

Therefore, the pH of the resulting solution is 3.16.

When weak acid is titrated with a strong base, the pH at the neutralization point is always greater than 7. It is because the conjugate base produced by weak acid in neutralization reaction is comparatively stronger in nature which produces [tex]OH^-[/tex] at neutralization point after reacting with water. so the solution is basic. As a result, pH is more than 7.

Now, the weaker is the acid, the stronger is the conjugate base, and vice-versa. Therefore, the concentration of [tex]OH^-[/tex] ions is more at the neutralization point. So more will be the pH value.

Given acids with the corresponding [tex]K_a[/tex] value are shown below:

[tex]K_a(HF) =6.8\times10^{-4}\\K_a(HNO_2) =4.5\times10^{-4}\\K_a(HClO_2) =1.1\times10^{-2}\\K_a(CH_3COOH) =1.8\times10^{-5}[/tex]

We know that lower the value of [tex]K_a[/tex] of  acid, the weaker is the acid and vice-versa. Hence, [tex]CH_3COOH[/tex] has lowest [tex]K_a[/tex] value compared to other acids. Therefore, [tex]CH_3COOH[/tex]  would  produce the highest pH at the equivalence point in a weak acid-strong base titration.

Hence, The pH of the resulting solution is 3.16. Acetic acid having the formula [tex]CH_3COOH[/tex] would produce the highest pH at the equivalence point in a weak acid-strong base titration.

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Answer:

0.696 m

Explanation:

We'll begin by calculating the number of mole in 16.7 g of C₆H₁₂O₆. This can be obtained as follow:

Mass of C₆H₁₂O₆ = 16.7 g

Molar mass of C₆H₁₂O₆ = (6×12) + (12×1) + (6×16)

= 72 + 12 + 96

= 180 g/mol

Mole of C₆H₁₂O₆ =?

Mole = mass / molar mass

Mole of C₆H₁₂O₆ = 16.7 / 180

Mole of C₆H₁₂O₆ = 0.093 mole

Next, we shall convert 133.6 g of water to Kg. This can be obtained as follow:

1000 g = 1 Kg

Therefore,

133.6 g = 133.6 g × 1 Kg / 1000 g

133.6 g = 0.1336 Kg

Thus, 133.6 g is equivalent to 0.1336 Kg.

Finally, we shall determine the molality of the solution. This can be obtained as illustrated below:

Mole of C₆H₁₂O₆ = 0.093 mole

Mass of water = 0.1336 Kg

Molality =?

Molality = mole / mass of water (in Kg)

Molality = 0.093 / 0.1336

Molality = 0.696 m

Therefore, the molality of the solution is 0.696 m

Answer:

If 13.50 mL of an aluminum chloride solution is needed to reach the equivalence point with 10.00 mL of 0.109 M silver nitrate solution, determine the molarity of the aluminum chloride solution.

Explanation:

The balanced chemical equation of the reaction is:

[tex]AlCl_3(aq)+3AgNO_3(aq)->3AgCl(s)+Al(NO_3)_3(aq)[/tex]

So, one mole of aluminum chloride reacts with three moles of silver nitrate.

At the equivalence point,

the number of moles of each reactant must be equal.

The number of moles = molarity x volume in L.

Number of moles of AlCl3 = volume x molarity

=0.0135Lx Molarity

The number of moles of AgNO3 = 3 x 0.010Lx 0.109M

Thus,

0.0135Lx Molarity = 3 x 0.010Lx 0.109M

Molarity of AlCl3 :

[tex]Molarity of Alcl_3=3 x 0.010Lx 0.109M/0.0135\\=0.242M[/tex]

Answer is : 0.242M.

Answer:

An indicator added to the solution turns green-blue.

Explanation:

An indicator is a substance which shows the degree of acidity or alkalinity of a solution by change in colour of the solution.

The universal indicator changes colour as the pH of the solution changes. Looking at the colour ranges for the universal indicator, the green-blue colour indicates a weak base.

Answer:

[tex]K=1.7x10^{-3}[/tex]

Explanation:

Hello there!

In this case, according to the given information, it turns out possible for us to solve this problem by firstly setting up the equilibrium expression for the given reaction, in agreement to the law of mass action:

[tex]K=\frac{[NO]^2}{[N_2][O_2]}[/tex]

Next, we plug in the given concentrations on the data table to obtain:

[tex]K=\frac{(0.034)^2}{(0.69)(0.98)}\\\\K=1.7x10^{-3}[/tex]

Regards!

Answer:

77%

Explanation:

First we convert 3.0 g of cyclohexanol (C₆H₁₂O) to moles, using its molar mass:

Then we convert 1.9 g of cyclohexene (C₆H₁₀) to moles, using its molar mass:

Finally we calculate the theoretical yield:

Answer:

The balanced net ionic equation is as follows:

CrO₄²- (aq) + 3 N₂O (g) + 2 H+ (aq) ----> Cr³+ (aq) + 6 NO (g) + H₂O (l)

The oxidizing agent is CrO₄²- as Cr⁶+ in CrO₄²- is reduced to Cr³+.

The reducing agent is N₂O as the nitrogen (i) is oxidized to nitrogen (ii).

Explanation:

The skeleton equation is given as follows:

CrO₄²- (aq) + N₂O(g)+ H+(aq) + OH-(aq) + H2O(l) ----> Cr³+(aq) + NO(g) + H+(aq) + OH-(aq) + H₂O(l)

The balanced net ionic equation with the spectator ions removed is as follows:

CrO₄²- (aq) + 3 N₂O (g) + 2 H+ (aq) ----> Cr³+ (aq) + 6 NO (g) + H₂O (l)

In a redox reaction, oxidizing agents are reduced while reducing agents are oxidized.

The oxidizing agent is CrO₄²- as Cr⁶+ in CrO₄²- is reduced to Cr³+.

One mole of CrO₄²- accepts three moles of electrons from three moles of N₂O to become reduced to 1 mole of Cr³+.

The reducing agent is N₂O as the nitrogen (i) is oxidized to nitrogen (ii).

Three moles of N₂O will each donate one mole of electrons to one mole of CrO₄²- to become oxidized to nitrogen (ii) oxide.

Hydrogen ions and a water molecule is added to the left-hand side and right-hand side of the equation respectively, in order to balance the number of oxygen atoms in the equation of the reaction.

Answer:

The heat absorbed in Trial 2 is about 1,240 J greater than the heat absorbed in Trial 1.

The heat absorbed in Trial 2 is about 1,674 J greater than the heat absorbed in Trial 1.

The amount of heat absorbed or released by a substance can be calculated using the formula Q = mcΔT, where Q represents heat, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature.

In this case, the mass (m) is the same in both trials, but the initial and final temperatures (ΔT) differ. By comparing the values of ΔT in both trials, we can determine the difference in the amount of heat absorbed.

In Trial 1, the initial temperature is 15.0 °C and the final temperature is 65.0 °C, resulting in a ΔT of 65.0 - 15.0 = 50.0 °C.

In Trial 2, the initial temperature is 10.0 °C and the final temperature is 65.0 °C, resulting in a ΔT of 65.0 - 10.0 = 55.0 °C.

Since the specific heat capacity of water is approximately 4.18 J/g°C, we can calculate the difference in heat absorbed:

ΔQ = mcΔT = (80.0 g)(4.18 J/g°C)(55.0 °C - 50.0 °C) = 1,674 J

Therefore, the heat absorbed in Trial 2 is approximately 1,674 J greater than the heat absorbed in Trial 1.

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For consumption of each gram of reactant released=37.9 kJ/g

Therefore, for consumption of 4kg of reactant heat released=37.9x4 kJ/g

If Gold's natural state has a definite shape and a definite volume, then its natural state is solid.

Answer:

Yes the reaction occur when aqueous solutions happened

Answer:

heat; temperature; surrounding; insulated.

Explanation:

A calorimeter can be defined as a scientific instrument (device) that is designed and developed for measurement of the heat involved in chemical reactions or other processes, especially by taking the measurement of the temperature of the materials surrounding the process.

Basically, a calorimeter is insulated using materials with a very high level of resistivity, so as to prevent heat transfer to the outside of the device (calorimeter).

Some of the components that make up a simple calorimeter are; thermometer, an interior styrofoam cup, an exterior styrofoam cup, cover, etc.

Additionally, a calorie refers to the amount of heat required to raise the temperature of a gram of water by one degree Celsius (°C)

A calorimeter measures the heat involved in reactions or other processes by measuring the temperature of the materials surrounding the process. The calorimeter is insulated to prevent transfer of heat to outside the device.

Calorimeter is an instrument used in chemical reactions for measuring the heat, physical changes as well as heat capacity of the chemical reaction.

From the definition of calorimeter it is clear that it checks the temperature of the reaction and calculates the heat of the chemical reaction. It is insulated by those materials which are bad conductors of heat so that no heat will loss from this apparatus.

Hence, correct options are heat, temperature, surroundings and insulated.

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Answer:

62.5 ml of 0.032 M  KMnO₄ are required to react with 50.0 ml of 0.100 molar H₂C₂O₄ in the presence of excess H₂SO₄

Explanation:

The balanced reaction is:

2 KMnO₄ + 5 H₂C₂O₄ + 3 H₂SO₄ → K₂SO₄ + 2 MnSO₄ + 8 H₂O + 10 CO₂

By stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:

Molarity or Molar Concentration is the number of moles of solute that are dissolved in a certain volume.

The molarity of a solution is calculated by dividing the moles of the solute by the volume of the solution:

[tex]Molarity=\frac{number of moles of solute}{volume}[/tex]

Molarity is expressed in units [tex]\frac{moles}{liter}[/tex]

In this case, 50 mL (0.05 L) of 0.1 M H₂C₂O₄ react. So, replacing the data in the definition of molarity:

[tex]0.1 M=\frac{number of moles of solute}{0.05 L}[/tex]

Solving:

number of moles of solute= 0.1 M*0.05 L

number of moles of solute= 0.005 moles

So, 0.005 moles of H₂C₂O₄ react.  Then you can apply the following rule of three: if by stoichiometry 5 moles of H₂C₂O₄ react with 2 moles of KMnO₄, 0.005 moles of H₂C₂O₄ react with how many moles of KMnO₄?

[tex]moles of KMnO_{4} =\frac{0.005moles of H_{2} C_{2} O_{4}* 2moles of KMnO_{4} }{5moles of H_{2} C_{2} O_{4} }[/tex]

moles of KMnO₄= 0.002 moles

Knowing that the molarity of KMnO₄ is 0.032 M, replacing in its definition and solving:

[tex]0.032 M=\frac{0.002 moles}{volume}[/tex]

[tex]volume=\frac{0.002 moles}{0.032 M}[/tex]

volume= 0.0625 L= 62.5 mL

62.5 ml of 0.032 M  KMnO₄ are required to react with 50.0 ml of 0.100 molar H₂C₂O₄ in the presence of excess H₂SO₄

Stalactites and stalagmites form as ________ precipitates out of the water evaporating in underground caves.

Group of answer choices

hydrochloric acid

sodium bicarbonate

calcium carbonate

sodium chloride

sodium hydroxide

Answer:

calcium carbonate

Explanation:

A stalactite is an icicle-looking mould that is formed by the precipitation of natural minerals as a result of water dripping from the ceiling, hanging from a cave.

A stalagmites in the other hand, grows upwards and is also a mound that is formed by the deposits of minerals gotten by the water dripping on the floor of a cave.

Therefore, stalactites and stalagmites form as calcium carbonate precipitates out of the water evaporating in underground caves.

Answer:

0.0063 mol

Explanation:

Step 1: Write the balanced combustion equation

C₈H₁₈(l) + 12.5 O₂(g) ⇒ 8 CO₂(g) + 9 H₂O(g)

Step 2: Establish the appropriate molar ratio

According to the balanced equation, the molar ratio of C₈H₁₈ to CO₂ is 1:8.

Step 3: Calculate the number of moles of C₈H₁₈ needed to produce 0.050 moles of CO₂

0.050 mol CO₂ × 1 mol C₈H₁₈/8 mol CO₂ = 0.0063 mol C₈H₁₈

Answer:  inference because she drew a conclusion based on evidence.

why?:

Because the evidence was that she heard the crashing sound, and then when she came into her room saw the broken window and baseball.

It was not an observation because she did not directly see the baseball going through the window

The properties of solids, liquids and gases regarding their shapes and volumes are:

                       Shape             Volume

Solids              Fixed                Fixed

Liquids           Variable            Fixed

Gases             Variable           Variable

Solids have strong attraction forces between their molecules. Thus, the molecules are closely packed with little movement. As a consequence, both shape and volume are fixed.

In liquids, attraction and repulsion forces are similar. They have a little more movement than the solid state. Then, they do have a fixed volume but they adopt the shape of the container.

Gases have very weak attraction forces between their molecules. They move very freely and expand trying to occupy as much volume as possible. So, they have a variable volume and shape (adopt the shape of the container).

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Answer:

Explanation:

Assume we have 100g of this substance. That means we would have 20.24g of Cl and 79.76g of Al. Now we can find how many moles of each we have:

[tex]\frac{79.76 \:g}{35.45 \: g/mol}[/tex] = 2.25 mol of chlorine

[tex]\frac{20.24 \: g}{26.98 \: g/mol}[/tex] = 0.750 mol of Al.

To form a integer ratio, do 2.25/0.75 = 2.99999 ~= 3.

So the ratio is essentially Al : Cl => 1 : 3. To the compound is possibly [tex]AlCl_3[/tex].

However, it says it has a molar mass of 266.64 g/mol, and since AlCl3 has a molar mass of 133.32, it must be [tex]Al_2Cl_6[/tex].

Actually this molecule isn't exactly AlCl3 (which is ionic). Al2Cl6 forms a banana bond where Cl acts as a hapto-2 ligand. But that's a bit advanced. All you need to know is X = Al2Cl6

The molecular formula of the compound is Al₂Cl₆

To solve the question given above, we'll begin by obtaining the empirical formula of the compound. This can be obtained as follow:

Aluminum (Al) = 20.24%

Chlorine (Cl) = 79.76%

Al = 20.24%

Cl = 79.76%

Divide by their molar mass

Al = 20.24 / 27 = 0.75

Cl = 79.76 / 35.5 = 2.25

Divide by the smallest

Al = 0.75 / 0.75 = 1

Cl = 2.25 / 0.75 = 3

Thus, the empirical formula of the compound is AlCl₃

Finally, we shall determine the the molecular formula of the compound.

Molar mass of compound = 266.64 g/mol

Empirical formula = AlCl₃

[AlCl₃]ₙ = 266.64

[27 + (3×35.5)]n = 266.64

[27 + 106.5]n = 266.64

133.5n = 266.64

Divide both side by 133.5

n = 266.64 / 133.5

Molecular formula = [AlCl₃]ₙ

Molecular formula = [AlCl₃]₂

Therefore, the molecular formula of the compound is Al₂Cl₆

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The volume of 1.5 moles of gas at STP  is 33.6 L.

The volume of the gas at STP is calculated as follows;

I mole of gas at STP = 22.4 L

1.5 moles of the gas at STP = ?

= 1.5 moles  x 22.4 L/mole

= 33.6 L

Thus, the volume of 1.5 moles of gas at STP  is 33.6 L.

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Explanation:

the reaction is a decomposition reaction since potassium hypochlorite is decomposed into potassium chloride and oxygen

Answer:

35g/l

Explanation:

Salinity is practically the saltiness of the water, in basic terms. It's basically the amount of salt dissolved in water. Ocean water has a salinity of around 35g/l (that's about 3.5% of which is dissolved salt in water!). However, Atlantic Ocean (the ocean with the saltiest water), can range up to 37g/l.

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b) (√)

c)(✓)

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Answer:

2.5 × 10² L

Explanation:

Step 1: Given and required data

Step 2: Convert 25 °C to Kelvin

We will use the following expression.

K = °C + 273.15 = 25 + 273.15 = 298 K

Step 3: Calculate the volume (V) of the balloon

We will use the ideal gas equation.

P × V = n × R × T

V = n × R × T / P

V = 9.7 mol × (0.0821 atm.L/mol.K) × 298 K / 0.955 atm = 2.5 × 10² L

Answer:

Increase

Decrease

Explanation:While in solution, ionic substances produce ions. The ions in solution determine the conductivity of the solution.

The ionic strength of a solution shows the concentration of ions in a given solution. The more the number of ions in the solution, the greater the ionic strength of the solution and vice versa.

When HNO3 is added to a solution of KOH, the number of ions in the solution increases and so does the ionic strength of the solution.

When KOH is added to a solution of CaCl2 then Ca(OH)2 is formed. The formation of a solid precipitate decreases the concentration of ions in solution as well as the ionic strength of the solution.

Answer:

Explanation:

When Tollen's test is done by aldehyde , silver ion is converted into silver which forms a layer which looks like a mirror.

Ag⁺ + e = Ag

It is a reduction process where silver(1) ion is reduced to metallic silver.

Aldehyde is oxidized to carboxylate ion.

CH₃CHO + 2 OH⁻ = CH₃COO⁻ + H₂O + H⁺ + 2e

Visual indicator is silver metal which forms silver mirror at the bottom of test tube .

Answer:

See explanation

Explanation:

The relationship between the activation energy and rate of reaction is best captured by the Arrhenius equation;

k= Ae^-Ea/RT

Where;

k= rate constant

A= pre-exponential factor

Ea=activation energy

R= gas constant

T= temperature

We can see from the foregoing that, as the activation energy increases, the rate of reaction decreases and vice versa. reactions that have a very high activation energy are markedly slow.

Since the activation energy for the malonic acid reaction is found to be greater than the activation energy for the tartaric acid reaction, then the rate of the malonic acid reaction(k) will be slower than that of the tartaric acid reaction.

The study of chemistry and bonds is called chemistry. There are two types of elements metal and nonmetals.

The correct answer is mentioned below.

The equation is as follows:-

[tex]k= Ae^{-Ea/RT[/tex] Where;

We can see from the foregoing that, as the activation energy increases, the rate of reaction decreases and vice versa. reactions that have very high activation energy are markedly slow. Since the activation energy for the malonic acid reaction is found to be greater than the activation energy for the tartaric acid reaction, then the rate of the malonic acid reaction(k) will be slower than that of the tartaric acid reaction.

Hence, the correct answer is mentioned above.

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