A student wants to remove the salt from a mixture of sand and salt in order to get only pure sand. He adds water to the mixture. Why is this step helpful?
A Salt dissolves in water.
B Sand dissolves in water.
C The water freezes to the salt.
D The salt floats on top of the water.

To calculate the mole fraction of acetone (C3H6O2) in a solution of water where equal masses of both compounds are present, we first need to determine the number of moles of each compound.
Since the masses are equal, we can assume that each compound has a mass of 50 grams (100g total). The molar mass of acetone is 58.08 g/mol, so 50 g of acetone is equal to 0.861 moles (50 g / 58.08 g/mol).
Therefore, the mole fraction of acetone in the solution is 0.237, which corresponds to answer choice (b).

To calculate the mole fraction of acetone (C3H6O) in a solution with equal masses of acetone and water, we first need to determine the moles of each substance.
The molecular weight of acetone is 58 g/mol (12*3 + 1*6 + 16), while the molecular weight of water is 18 g/mol (1*2 + 16).
Assuming 100 g of the solution, we have 50 g of acetone and 50 g of water (equal masses). To find the moles, we use the formula moles = mass/molecular weight:
Moles of acetone: 50 g / 58 g/mol = 0.862 moles
Moles of water: 50 g / 18 g/mol = 2.778 moles
Now, we can calculate the mole fraction of acetone using the formula mole fraction = moles of component / total moles:
Mole fraction of acetone: 0.862 moles / (0.862 + 2.778) moles ≈ 0.237
Therefore, the mole fraction of acetone in the solution is approximately 0.237, which corresponds to option b.

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Answer:

m = 16.67 g of Hg

Explanation:

Let's write the overall decomposition reaction that is taking place:

2HgO ---------> 2Hg + O₂

According to the balanced reaction, we can see that the mole ratio between HgO and Hg is the same (2:2 or 1:1), therefore, we can assume that the moles reactants of HgO would be the moles produced of Hg. So, in order to get the grams of mercury, we need to determine the moles first.

To get the moles, we need to use the following expression:

moles = mass / MM   (1)

The molar mass of HgO can be calculated using the atomic weights, which are:

Hg: 200.59 g/mol ; O: 15.999 g/mol

MM HgO = 200.59 + 15.999 = 216.589 g/mol

The moles are:

moles HgO = 18 / 216.589 = 0.0831 moles

As we stated before, moles reactants are the same moles produced, so:

moles HgO = moles Hg = 0.0831 moles of Hg.

Finally, to get the mass, we just solve the mass from (1):

m = moles * MM   (2)

m = 0.0831 * 200.59

Hope this helps

In Chemistry, we always have to balance the equations, in many topics within the subject of Chemistry, it is required to do that, this is because we have to account for every atom in the reaction, on both sides, reactant and product, the same number of atoms that are on the reactants side must be on the products side. Therefore, the best answer for this question will be letter D

The formation of a positively charged molecule consisting of three hydrogen atoms bonded to an oxygen atom can occur through the gain of a hydrogen ion from another water molecule, resulting in a hydronium ion (H3O+).

This positively charged molecule can also be formed through the bonding of a hydrogen molecule with an OH- molecule, or by the combination of two water molecules.

Evaporation, on the other hand, refers to the process by which a liquid water molecule transitions to a gaseous state, which is not directly related to the formation of the described positively charged molecule.

The formation of a positively charged molecule with three hydrogen atoms bonded to an oxygen atom can occur through different processes. One possibility is the gain of a hydrogen ion (H+) from another water molecule, resulting in the formation of a hydronium ion (H3O+). In this case, the hydrogen ion is attracted to the oxygen atom in the water molecule, leading to the formation of the positively charged molecule.

Another possibility is the bonding of a hydrogen molecule (H2) with an OH- molecule (an hydroxide ion). This results in the formation of the described molecule, where the hydrogen atoms are bonded to the oxygen atom.

Additionally, two water molecules can combine, resulting in the formation of the described molecule. The oxygen atom in one water molecule can share its electrons with the hydrogen atoms from another water molecule, creating the bonding arrangement described.

However, evaporation refers to the process by which liquid water molecules transition to a gaseous state, where individual water molecules escape the liquid phase due to increased kinetic energy. While evaporation is an important phenomenon, it does not directly relate to the formation of the specific positively charged molecule described.

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When 15.5 moles of \(HNO_3\) are consumed, 72.06 grams of water can be produced.

The balanced chemical equation for the reaction between copper and nitric acid is:

\(3Cu + 8HNO_3\ - > 3Cu(NO_3)_2 + 2NO + 4H_2O\)

Therefore, to calculate the amount of water produced, we first need to determine how many moles of \(HNO_3\) are consumed when 15.5 moles are present:

Moles of \(HNO_3\) consumed = 8/15.5 x 15.5 moles = 8.00 moles

Stoichiometry  can be used to calculate the amount of water produced:

Moles of \(H_2O\) produced = 4/8 x 8.00 moles = 4.00 moles

Calculating mass of water produced using its molar mass:

Mass of \(H_2O\) produced = moles of \(H_2O\) produced x molar mass of \(H_2O\)

Mass of \(H_2O\) produced = 4.00 moles x 18.015 g/mol = 72.06 g

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--The complete Question is,3Cu + 8HNO3 → 3Cu(NO3)2 + 2NO + 4H2O

In the above equation how many grams of water can be made when 15.5 moles of HNO3 are consumed? --

The number of moles of Ca(OH)₂ produced from  from 49 grams of H₂O is 1.36 mole

First, we shall determine the mole in 49 grams of water, H₂O. Details below:

Mole = mass / molar mass

Mole of H₂O = 49 / 18

Mole of H₂O = 2.72 moles

Finally, we shall determine the number of mole of Ca(OH)₂ produced. This is illustrated below:

Ca + 2H₂O → Ca(OH)₂ + H₂

From the balanced equation above,

2 moles of H₂O reacted to produce  moles of Ca(OH)₂

Therefore,

2.72 mole of H₂O will react to produce = (2.72 × 1) / 2 = 1.36 mole of Ca(OH)₂

Thus, from the above calculation, we can conclude that the number of mole of Ca(OH)₂ produced is 1.36 mole

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PbCl2 is insoluble in water.

To determine which one of the following compounds is insoluble in water, let's evaluate each option:

1. CaCl2 (Calcium chloride)
2. NaNO3 (Sodium nitrate)
3. PbCl2 (Lead(II) chloride)
4. K2CO3 (Potassium carbonate)

According to solubility rules, most chloride (Cl-) salts are soluble, with some exceptions like AgCl, PbCl2, and Hg2Cl2. Most nitrate (NO3-) salts and alkali metal salts (like those containing Na+ and K+) are soluble in water.

Based on these rules:
- CaCl2 is soluble (calcium chloride)
- NaNO3 is soluble (sodium nitrate)
- K2CO3 is soluble (potassium carbonate)

However, PbCl2 (lead(II) chloride) is an exception and is considered insoluble in water.

So, the answer to your question is: PbCl2 (Lead(II) chloride) is the compound that is insoluble in water among the given options.

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Answer:

lithium

Explanation:

lithium is the only atom with 3 protons.

Unlike protons and neutrons, which are housed inside the atom's nucleus at its center, electrons are found outside the atom.

An atom can have a label in addition to a symbol or atomic number. The label is formatted as "(text)" (without the quotation marks), which means "text, closed curved bracket, open curved bracket." If an isotopic mass is present, it should come after the chemical symbol, followed by the label.

The element is represented by the letter(s) in the centre. The atomic number, which indicates the quantity of protons, is the number in the bottom left corner.

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The correct answer is: D. All of the above.

In the chemical reaction 2Al(s) + 3Pt(NO3)2(aq) -> 3Pt(s) + 2Al(NO3)3(aq), we can determine the role of Al(s) by examining the changes in oxidation states.

The reducing agent: A reducing agent is a substance that undergoes oxidation, meaning it loses electrons, and causes the reduction of another species by donating electrons. In this reaction, Al(s) is oxidized from an oxidation state of 0 to +3 in Al(NO3)3(aq). Therefore, Al(s) is not the reducing agent.

The electron donor: An electron donor is a substance that donates electrons to another species. In this reaction, Al(s) donates electrons to Pt(NO3)2(aq), resulting in the reduction of Pt(II) ions to Pt(s). Therefore, Al(s) acts as the electron donor.

Being oxidized: When a substance undergoes oxidation, it loses electrons and increases its oxidation state. In this reaction, Al(s) is oxidized from an oxidation state of 0 to +3 in Al(NO3)3(aq). Therefore, Al(s) is being oxidized.

From the analysis above, we can conclude that the correct answer is:

D. All of the above

Al(s) is the electron donor, it undergoes oxidation and loses electrons, and therefore acts as the reducing agent in this chemical reaction. It is important to note that in redox reactions, the species that is oxidized is the reducing agent, and the species that is reduced is the oxidizing agent.

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The correct statements that describe the procedure for drawing a Lewis structure are:

c. For a neutral molecule, the sum of the number of valence electrons for each atom gives the number of electrons used in the Lewis structure.

e. An electron is added to the total count for each negative charge on the species.

a. This assertion is untrue. If two atoms are joined by a bond, a single bond representing two electrons should be placed between them; however, not every pair of atoms in the Lewis structure must be linked by a connection.

b. This assertion is untrue. Since they increase the number of valence electrons and have an impact on the overall structure, nonbonding electrons, sometimes referred to as lone pairs, should be included in the Lewis structure.

d. This assertion is untrue. Halogen atoms are typically not positioned in the structure's center. The arrangement of formal charges of the atoms in a molecule and their overall electronegativity determine where they are placed in a Lewis structure.

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To draw a Lewis structure, you should place single bonds between atoms, include nonbonding electrons, and use the sum of the valence electrons for a neutral molecule.

The correct statements that describe the procedure for drawing a Lewis structure are:

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The specific heat of lead for 100g sample to water at 25. 3 degrees Celsius was placed in a calorimeter is 0.131 J/g°C.

To solve for the specific heat of lead, we can use the formula:

q = mcΔT

Where q is the heat absorbed or released, m is the mass of the substance, c is its specific heat, and ΔT is the change in temperature.

We can first calculate the heat absorbed by the water:

q_water = m_water × c_water × ΔT_water

= 100g × 4.18 J/g°C × (34.4°C - 25.3°C)

= 3784 J

We can then calculate the heat released by the lead:

q_lead = m_lead × c_lead × ΔT_lead

= 45g × c_lead × (100°C - 34.4°C)

= 1962g × c_lead

Since the heat lost by the lead is equal to the heat gained by the water, we can set these two equations equal to each other:

q_lead = q_water

1962g × c_lead = 3784 J

Solving for c_lead, we get:

c_lead = 3784 J / (1962g × (100°C - 34.4°C))

= 0.131 J/g°C

Therefore, the specific heat of lead is 0.131 J/g°C.

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Answer

63.55

Explanation:

63

C

u

 has

69.2

%

abundance.

65

C

u

has

30.8

%

abundance.

So, the weighted average is

62.93

×

69.2

%

+

64.93

×

30.8

%

When, shaft rotates at 3500 rpm and the bearing will be subjected to radial load of 1000 and a thrust load of 250 N. Then, the estimated bearing life for 90% reliability is 43,600 hours.

To estimate the bearing life, we can use the following formula;

L₁₀ = (C/P)³ x (10/3) x 60 x n

where; L₁₀ = estimated bearing life in hours for 90% reliability

C = basic dynamic load rating of bearing

P = equivalent dynamic bearing load

n = rotational speed of the bearing in revolutions per minute

To find C, we need to know the bearing's size and type. Let's assume it is a standard size 6205 deep groove ball bearing with a dynamic load rating of 14.3 kN.

To find P, we need to calculate the equivalent dynamic bearing load, which is a combination of the radial and thrust loads. We can use the following formula;

P = (X\(F_{r}\) + Y\(F_{a}\))

where;

\(F_{r}\) = radial load

\(F_{a}\) = thrust load

X and Y are factors that depend on the bearing's design and can be found in bearing catalogs or tables. For a 6205 bearing, X = 0.56 and Y = 1.5.

Plugging in the values, we get;

P = (0.56 x 1000 + 1.5 x 250)

= 935 N

Finally, we can calculate the estimated bearing life;

L₁₀ = (14.3/935)³ x (10/3) x 60 x 3500

= 43,600 hours

Therefore, the estimated bearing life is 43,600 hours.

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Answer: The reaction that occurs at anode is \(Zn(s)\rightarrow Zn^{2+}(aq.)+2e^-\)

Explanation:

Given : \(E^o_{Zn^{2+}/Zn}=-0.76V\)

\(E^o_{Cu^{2+}/Cu}=+0.34V\)

The substance having highest positive reduction potential will always get reduced and will undergo reduction reaction. Here, copper will undergo reduction reaction will get reduced.

The substance having highest negative reduction potential will always get oxidised and will undergo oxidation reaction. Here, zinc will undergo oxidation reaction will get oxidised.

Oxidation reaction occurs at anode and reduction reaction occurs at cathode.

Oxidation half reaction (anode) : \(Zn(s)\rightarrow Zn^{2+}(aq.)+2e^-\)

Reduction half reaction (cathode) : \(Cu^{2+}(aq.)+2e^-\rightarrow Cu(s)\)

Molecules are the smallest chemical units of matter that retain the chemical properties of a substance. They are formed by the combination of two or more atoms held together by chemical bonds, either through sharing or transfer of electrons.

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Answer:

In the elemental form, non-metals can be gas, liquid or solid. They aren't shiny (lustrous) and they don't conduct heat or electricity well. Usually their melting points are lower than for metals, although there are exceptions. The solids usually break easily, and can't bend like metals

Explanation:

Answer: Br2 I2 N2 Cl2 H2 O2 F2 (7 elements)

Explanation:

How to remeber this: Hal-NOH or BrINCIHOF

halogens Nitrogen, Oxygen, and Hydrogen.

False. Both random and systematic errors can have an impact on experimental data.

Random mistakes are generated by unpredictability in measuring settings and are typical of minor magnitude. In contrast, systematic mistakes are generated by systematic biases in the experimental technique and result in a constant divergence from the correct value.

If Alejandro's results differ greatly from those of his neighbors, it could be due to chance, but it could also be due to systemic flaws in his experiment. Without more examination, Alejandro cannot assume that the variance is purely due to random mistakes. He should thoroughly examine his experimental approach for potential sources of systematic error. It may also be beneficial to repeat the experiment to establish whether the discrepancy is due to random error or if it is consistent.

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The volume of the gas is 1.27 L at a temperature is 47°C and the pressure is 5.0 atm. Therefore, option (B) is correct.

The ideal gas equation is described as the equation of the state of a perfect gas. The ideal gas equation is the product of the pressure and volume of one-mole gas is equal to the multiplication of the absolute temperature and gas constant.

The mathematical equation for a perfect gas is as follows:

PV = nRT

where n is the moles of an ideal gas, P is the pressure of the gas,  V is the volume, and R is the universal gas constant.

Given, the initial volume of the gas, V₁ = 2.0 L

The initial temperature of the gas, T₁ =  27° C = 300.15 K

The initial pressure of the gas, P₁ = 3.0 atm

The final temperature of the gas, T₂ =  47° C = 320.15 K

The initial pressure of the gas, P₂ = 5.0 atm

We know that for an ideal gas:

\(\frac{P_1V_1}{T_1} =\frac{P_2V_2}{T_2}\)

\(V_2=\frac{P_1V_1T_2}{T_1P_2}\)

\(V_2= \frac{3.0\times2.0\times320.15}{5.0\times 300.15}\)

\(V_2= 1.27 L\)

Therefore, the volume of the gas in its final state is equal to 1.27 L when the gas is heated to 47ºC and compressed to 5.0 atm.

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Recovery = (Weight of product recovered ÷ Theoretical yield) × 100% Recovery = (0.251 g ÷ 0.27594 g) × 100% Recovery = 91.08%Therefore, the % recovery of the reaction between 2,3-dimethyl-1,3-butadiene and maleic anhydride to form cyclic anhydride was 91.08%.

Diels-Alder Reaction   Diels-Alder reaction is a chemical process that joins a conjugated diene with a dienophile (a compound containing a double bond) to form a six-membered ring called a cyclohexene ring. It is a chemical reaction that can be used to make new carbon–carbon bonds. The reaction was discovered by two German scientists, Otto Diels and Kurt Alder, in 1928.In the Diels-Alder reaction between 2,3-dimethyl-1,3-butadiene and maleic anhydride to form cyclic anhydride, the % recovery was calculated using the following data:Weight of maleic anhydride used: 185 mg = 0.185 gVolume of diene used: 0.215 mLWeight of cyclic anhydride crystals recovered: 0.251 g% Recovery:We can calculate the percent recovery using the following formula:% Recovery = (Weight of product recovered ÷ Theoretical yield) × 100The theoretical yield of the product can be calculated from the balanced chemical equation as follows:2,3-dimethyl-1,3-butadiene + Maleic Anhydride → Cyclohexene-1,2-dicarboxylic AnhydrideThe molar mass of 2,3-dimethyl-1,3-butadiene is 68 g/mol. The molar mass of Maleic Anhydride is 98 g/mol. The molar mass of Cyclohexene-1,2-dicarboxylic Anhydride is 146 g/mol.Using these values, we can calculate the number of moles of each reactant: moles of diene used = (0.215 mL)(0.788 g/mL)/(68 g/mol) = 0.00248 mol moles of maleic anhydride used = 0.185 g/98 g/mol = 0.00189 mol The theoretical yield of cyclohexene-1,2-dicarboxylic anhydride = 0.00189 mol × 1 mol/1 mol = 0.00189 molThe theoretical yield of cyclohexene-1,2-dicarboxylic anhydride = 0.00189 mol × 146 g/mol = 0.27594 gNow, we can substitute these values into the percent recovery equation:% Recovery = (Weight of product recovered ÷ Theoretical yield) × 100% Recovery = (0.251 g ÷ 0.27594 g) × 100% Recovery = 91.08%Therefore, the % recovery of the reaction between 2,3-dimethyl-1,3-butadiene and maleic anhydride to form cyclic anhydride was 91.08%.

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70 g of a solid solute is added to 50 g of water at 20 °c, and it all dissolves. when additional solute is added, it does not dissolve. KI is the solute.

What is solute ?

A solute is a substance that has dissolved in a solution. Molecules of the solvent often outnumber those of the solute in a fluid solution. In our daily lives, salt and water are two of the most prevalent solutes. Salt becomes a solute when it is dissolved in water.

What is solvent?

Solvents are employed to dissolve the substances that serve as the formulation's solutes. The components of these solutes can be solids, liquids, or gases. The use of a suitable solvent in conjunction with the solute is required to create a solution.

given: 70g of solute is added to 50g of water at 20degree C

solution: at 20degree C,

since graph is for 100g of water

multiple by 2

2 x 50g of water=100g of water

similarly 2 x 70g of solute= 140g of solute

at 20degree C, The solute KI falls at 140g

Therefore , KI is the solute

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Answer:

The correct option is;

Element 2

Explanation:

The ionization energy is the energy required to eject an electron from a gaseous ion or atom

The ionization energy increases across the period and increases up the group

The elements with the highest ionization energy are those that have the complete octet structure in their outermost shell, which are the noble gases

Therefore, given that element 2, which has the complete octet structure in the outermost shell, then it is an element of the noble gases which have the highest ionization energy in a period, and therefore has the highest ionization energy.

On the periodic table, the element with 10 electrons is Neon, with ionization energy of 2080.68 kJ/mol which is the second highest after helium, that has only 2 electrons.

The statements that describe how the pond turned into the bog is as follows: Large water plants grew in shallow water around the edge of the pond.

Pond is an inland body of standing water, either natural or man-made, that is smaller than a lake.

A bog is an area of decayed vegetation (particularly sphagnum moss) which forms a wet spongy ground too soft for walking.

This means that a pond can become a bog when existing plants in the pond decays until the land becomes soft.

Therefore, the statements that describe how the pond turned into the bog is as follows: Large water plants grew in shallow water around the edge of the pond.

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Answer:

hydration

increase of the surface area of the solute

Answer:

B & C

Explanation:

B. hydration

C. increase of the surface area of the solute

Answer:

Explanation:

solar cell - converts sunlight into electricity

geothermal energy - heat produced within the Earth​

wave energy - turns turbines along coastlines

hydroelectricity - water falling through dams turns turbines, generates electricity

Answer:

Explanation:

The renewable energy sources are:  solar cell, geothermal, wave and hydroelectricity.  Their descriptions are as follows:

converts sunlight into electricity -> solar cell

energy turns turbines along coastlines -> wave

water falling through dams turns turbines, generates electricity -> hydroelectricity

heat produced within the Earth​ -> geothermal