1. 7.85 g of sodium metal is added to 200 mL of 0.0450 M HNO3

a) Predict the mass of the precipitate
b) Predict the amount of excess reagent left over
c) Volume of gaseous product at STP conditions

Answer:

Volume is always more than the mass for floating objects. For sinking objects mass is always more than the volume

Explanation:

None

An ice storm is a temperature below freezing resulting from large amount of snow falling, i.e., options A and B.

Freezing rain causes ice storms. Raindrops travel into a tiny layer of below-freezing air near the earth's surface, where they freeze on contact with the ground, trees, automobiles, and other things.

Ice forms when cold rain freezes in contact with surfaces below the freezing point.

Thus, the correct options A and B.

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a and e are heterogeneous (door and salsa), b, c, and d are homogeneous (air, black coffee, and pure water), and f cannot be classified as it pertains to a person rather than a substance or mixture. Option A and E

a. A door: Heterogeneous. A door is typically made up of various materials such as wood, metal, glass, etc. These materials have different properties and can be easily distinguished, making the door a heterogeneous object.

b. The air you breathe: Homogeneous. Air is a mixture of gases, primarily nitrogen, oxygen, carbon dioxide, and trace amounts of other gases. On a macroscopic scale, air appears uniform and consistent throughout, making it a homogeneous mixture.

c. A cup of coffee (black): Homogeneous. A cup of black coffee consists of water and coffee solutes that are evenly distributed throughout the liquid. It appears uniform and consistent, indicating a homogeneous mixture.

d. The water you drink: Homogeneous. Pure water, without any dissolved substances or impurities, is a homogeneous substance. It is composed of H2O molecules that are uniformly distributed throughout the liquid.

e. Salsa: Heterogeneous. Salsa is a mixture of various ingredients such as tomatoes, onions, peppers, and spices. These ingredients have different textures, colors, and sizes. The different components can be visually distinguished, making salsa a heterogeneous mixture.

f. Your lab partner: Heterogeneous. A lab partner refers to a person, and individuals are not considered homogeneous or heterogeneous in the same sense as substances or mixtures. They are complex beings with different physical characteristics, thoughts, and behaviors. Thus, categorizing a lab partner as homogeneous or heterogeneous is not applicable in this context. Option A and E

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Answer: Hydrogen-H

Explanation: Hydrogen is a gas, the most abundant element in the universe and the simplest of them all

Answer:

4.70 grams of NH4Cl is needed to prepare 350 mL of a 0.25 M ammonium chloride solution.

We need approximately 4.68 grams of NH4Cl to prepare a 0.25 M ammonium chloride solution with a volume of 350 mL.

To determine the mass of NH4Cl needed to prepare the solution, we us use the formula:

m=M x V x MM ... (i)

where,

m= mass in grams

M=molarity of solution

MM= molar mass of compound

V= volume in litres

The number of moles of NH4Cl needed can be calculated using:

  Moles = Molarity x Volume ...(ii)

  Moles = 0.25 mol/L x 0.350 L

  Moles = 0.0875 mol

Hence we can replace M x V with number of moles in equation i.

The molar mass of NH4Cl is :

  Molar mass of NH4Cl = (1 x 14.01 g/mol) + (4 x 1.01 g/mol) + (1 x 35.45 g/mol)

  Molar mass of NH4Cl = 53.49 g/mol

We have all the variables

Putting them in equation i.

Hence,

  Mass (g) = Moles x Molar mass

  Mass (g) = 0.0875 mol x 53.49 g/mol

  Mass (g) = 4.68 g

Therefore, you would need approximately 4.68 grams of NH4Cl to prepare a 0.25 M ammonium chloride solution with a volume of 350 mL.

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The mass of NaCl required ( in grams) to make the aqueous solution is 1.287 g.

What is molecular mass? How do you calculate molecular mass?

A molecule's mass is the sum of the masses of all the atoms it contains. As it is the total mass of all the atoms in a molecule, it is calculated below

The molecular mass of NaCl = Atomic mass of Na + Atomic mass of Cl

                                               = 23 + 35.5

                                               = 58.5g/mol

Given the volume of aqueous solution = 120.4 ml or 0.1204 L

Molarity of solution = 0.183M

We know that,

Molarity = No. of moles/Volume

No. of moles = 0.183 × 0.1204

                      =  0.022 moThe molar.

Molar mass of NaCl = Mass of Na + Mass of Cl

                                 = 23 + 35.5

                                 = 58.5g/mol

Mass of NaCl = 0.022 × 58.5

                      = 1.287 g

So, the mass of NaCl required ( in grams) to make the aqueous solution is 1.287 g.

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Isomers are compounds that have the same molecular formula, meaning they contain the same types and numbers of atoms but differ in their structural arrangement or spatial orientation.

The five possible isomers corresponding to the formula C7H16, along with their names:

1.  Heptane:

    CH3-CH2-CH2-CH2-CH2-CH2-CH3

2. 2-Methylhexane:

    CH3-CH2-CH(CH3)-CH2-CH2-CH3

3. 3-Methylhexane:

    CH3-CH2-CH2-CH(CH3)-CH2-CH3

4. 2,2-Dimethylpentane:

    CH3-C(CH3)2-CH2-CH2-CH3

5. 2,3-Dimethylpentane:

    CH3-CH(CH3)-CH(CH3)-CH2-CH3

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The concentration of NO3-N in mg/L = 10 mg/L.

The given water sample contains 10 mg NO3/L.

To find the concentration of NO3 in millimoles/L:

1 mg = 1/1000 g1 mole of NO3 contains 1 + 3x16 = 61 g NO3So, 1 g NO3 = 1/61 mole NO3

Thus, 10 mg NO3 contains (10/1000) * (1/61) mole of NO3= 0.000163934426 mole of NO3

Therefore, the concentration of NO3 in millimoles/L = 0.000163934426 * 1000= 0.163934426 millimoles/L

To find the concentration of NO3-N in mg/L:1 mole of NO3 contains 1 mole of N= 14 g N

Thus, 1 g NO3-N = 1/14 mole of NO3-N

Therefore, 10 mg NO3-N contains (10/1000) * (1/14) mole of NO3-N= 0.000714285714 mol of NO3-N

Therefore, the concentration of NO3-N in mg/L = 0.000714285714 * 14000= 10 mg/L.

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A valid Lewis structure of SO3 cannot be drawn without the central atom violating the octet rule. The correct option is b.

The octet rule states that atoms tend to gain, lose, or share electrons in order to achieve a stable electron configuration with eight electrons in their outermost shell.

In the case of SO3, sulfur (S) is the central atom surrounded by three oxygen (O) atoms. Each oxygen atom needs two electrons to complete its octet, while sulfur needs six electrons to complete its octet.

However, if we distribute the electrons according to the octet rule, each oxygen atom would share two electrons with sulfur, leaving sulfur with only six electrons.

One possible Lewis structure for SO3 is to form a double bond between sulfur and one oxygen atom and single bonds with the remaining two oxygen atoms. In this structure, sulfur has ten electrons around it, violating the octet rule.

The Lewis structure would look like this:

O

//

S

\

O

To accommodate the octet rule, sulfur in SO3 can expand its valence shell by utilizing its empty d orbitals. This allows sulfur to accommodate more than eight electrons around it, but it violates the octet rule.

In summary, a valid Lewis structure of SO3 cannot be drawn without the sulfur atom violating the octet rule because sulfur would require more than eight electrons to satisfy the octet rule. The correct option is b.

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Answer: Entropy

Explanation: Entropy. A measure of the level of disorder of a system is entropy, represented by S

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The given chemical equation is: 3Cu + 8HNO3 → 3Cu(NO3)2 + 2NO + 4H2O1Oxygen16Now, let us balance the given chemical equation by following the Law of Conservation of Mass.Balancing the chemical equation: 3Cu + 8HNO3 → 3Cu(NO3)2 + 2NO + 4H2O1Oxygen16Number of atoms on both sides of the chemical equation should be the same. Let's check one by one.Number of Copper (Cu) atoms:

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Answer: Ionic attractions

Explanation:

Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions.

Answer:

When a liquid is 140° F it really only takes five or less seconds to produce a serious burn.

The term "Lewis base" refers to a molecule or ion that can donate a pair of electrons to form a coordinate bond with a metal or metalloid center. In the given options, CH3NH2 (methylamine) is a Lewis base because it has a lone pair of electrons on the nitrogen atom that can act as a donor. BeCl2 (beryllium chloride) can also act as a Lewis base because it has two empty orbitals that can accept a pair of electrons from a Lewis acid.

Therefore, options C and E are correct, and the answer is either C) CH3NH2, BeCl2 or E) CH3NH2 only, depending on whether BeCl2 is considered a Lewis base or not. Cr3+ and SO3 are not Lewis bases because they do not have any lone pair of electrons to donate.

A Lewis base is a molecule or ion that can donate an electron pair to form a coordinate covalent bond with a Lewis acid. Among the given options, we need to find which ones can act as a Lewis base.

Cr3+ is a cation and does not have an electron pair to donate, so it cannot act as a Lewis base.

SO3 is a molecule with all its oxygen atoms double-bonded to the sulfur atom, so it does not have any lone pair to donate, and thus, cannot act as a Lewis base.

CH3NH2 (methylamine) has a lone pair of electrons on the nitrogen atom, making it a good candidate to donate an electron pair and act as a Lewis base.

BeCl2 is an electron-deficient molecule and would rather accept a lone pair of electrons, acting as a Lewis acid, not a base.

Considering these explanations, the correct answer is:

E. CH3NH2 only

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Answer:Oxygen has 6 valence electrons

A=2

B=2

C=4

The charge of an oxygen Ion is -2

Explanation:

According to the electronic configuration,there are 6 valence electrons in an oxygen atom.

Electronic configuration is defined as the distribution of electrons which are present in an atom or molecule in atomic or molecular orbitals.It describes how each electron moves independently in an orbital.

Knowledge of electronic configuration is necessary for understanding the structure of periodic table.It helps in understanding the chemical properties of elements.

Elements undergo chemical reactions in order to achieve stability. Main group elements obey the octet rule in their electronic configuration while the transition elements follow the 18 electron rule. Noble elements have valence shell complete in ground state and hence are said to be stable.

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Answer:

Explanation:

Most molecular compounds that have a mass similar to water are gases at room temperature. Because of the strong hydrogen bonds, water molecules are able to stay condensed in the liquid state, but, because of the hydrogen bonds, as water molecules come together they stick to one another for a small, but significant amount of time. Molecular water, therefore, is a liquid at room temperature

Answer:

4. they have the same number of protons

Explanation:

while all the other particles and attributes can be changed, protons cannot.

Answer:

The correct answer is Choice C.

(Phenol red indicator.)

Explanation:

Phenol red indicator is an organic dye that acts as an acid-base reaction indicator in the pH range of 6.8 to 8.4.

In acidic solutions, the color is purple, and in simple solutions, the color is red.

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Answer:

phenol red indicator

Explanation:

Answer:

blue only

Explanation:

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The Toyota Prius basic trim in 2022 has the highest gas mileage ratings in its class. It states that it gets 56 MPG overall, 58 MPG in the city, and 53 MPG on the highway.

A Toyota Prius's gas mileage varies based on the model year, the road's conditions, and the driver's behaviour. Yet, the Prius is one of the most fuel-efficient cars on the market and is well renowned for its fuel efficiency. The combined city/highway gas mileage for the most current Prius models is expected to be between 54 and 58 miles per gallon. A hybrid powertrain, which combines an electric motor with a gasoline engine, enables the car to run on electricity at low speeds and during acceleration while the gasoline engine supplies power at greater speeds, is what allows for this good gas mileage.

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Conduction, radiation, and convection are the three different ways that thermal energy is transferred. Only fluids experience the cyclical process of convection.

Internal energy is transferred during thermal energy transfer. Conduction, convection, and radiation are the three different ways that thermal energy may be transferred. Atoms come into touch directly during conduction, heated particles move during convection, and electromagnetic waves travel during radiation.

When the temperature rises, atoms and molecules move faster and collide, creating thermal energy (also known as heat energy). Thermal energy is the energy that results from the heated substance's temperature.

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Answer:

i beleive iron

Explanation:

The main function of using a virtual spectrometer in order to analyze astronomical bodies in space is to find the chemical composition of planets and stars.

This refers to the instrument that is used to observe the color separation of light in a controlled experiment.

Hence, we can see that another reason for the use of a virtual spectrometer to make an analysis of astronomical bodies is to indicate the speed and direction of a star or galaxy as it spreads incoming beams of light into different spectrums.

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Answer:

O Ca(OH)2

Explanation:

According to Arrhenius definition of a base, it is a substance that dissociates in water to form hydroxide ions (OH-). This means that in the neutralization reaction between calcium hydroxide and sulfuric acid as described in this question, calcium hydroxide is the base because it contains the hydroxide ion (OH-).

Calcium hydroxide is a combination of calcium (Ca2+) as the cation and hydroxide (OH-) as the anion. Hence, the chemical formula will be Ca(OH)2.

Answer:

C3H8

Explanation:

1 1.5mol

2 0.75mol

3 0.667mol

Questions 1.2

1 16.7mol

2 8.3×10−3mol

Questions 1.3

1 9

2 11

3 12

4 24

5 22

Questions 1.4

1 a) 151.9

b) 162.1

c) 60.0

d) 132.1

e) 388.8

2 a) 0.5mol

b) 2.5mol

c) 0.6mol

d) 2.0mol

e) 0.38mol

3 a) 180.6g

b) 44.46g

Questions 1.5

1 Mr = 277.9 moles of oxygen = 11

2 Mr = 474.3 moles of oxygen = 20

Questions 1.6

1 Cu2S

2 C3H8

3 CaFe2O4

Questions 1.7

1 a) 2H2 + O2 → 2H2O

b) I2 + 3Cl2 → 2ICl3

c) NaOH + Al(OH)3 → NaAlO2 + 2H2O

d) 2H2S + SO2 → 3S + 2H2O

e) 4NH3 + 3O2 → 2N2 + 6H2O

2 a) MgCO3 → MgO + CO2

b) Pb(s) + 2AgNO3(aq) → Pb(NO3)2(aq) + 2Ag(s)

c) Na2O(s) + H2O(l) → 2NaOH(aq)

d) 2FeCl2 + Cl2 → 2FeCl3

e) Fe2(SO4)3 + 6NaOH → 2Fe(OH)3 + 3Na2SO4

Questions 1.8

1 17.0g

2 60.7g

3 51.1%

Questions 1.9

1 1.2dm3

2 Volume of SO2 = 50cm3; mass of sulfur = 0.20g

Questions 1.10

1 a) 2.67moldm−3

b) 0.025moldm−3

c) 0.833moldm−3

2 a) 0.75mol

b) 0.044mol

c) 0.010mol

Answer:A hypothesis is a tentative explanation that can be tested by further investigation. A theory is a well-supported explanation of observations. A scientific law is a statement that summarizes the relationship between variables. An experiment is a controlled method of testing a hypothesis.

Explanation:

All of the following are qualitative tests that are often used to identify unknown ionic compounds except titration.

Qualitative tests are conducted to determine the presence or absence of certain ions or compounds in a sample based on their characteristic reactions. Common qualitative tests include flame tests, precipitation reactions, color changes, and gas evolution tests.

Titration, on the other hand, is a quantitative technique used to determine the concentration of a specific substance in a solution by reacting it with a standardized solution of another substance. It is not typically used as a qualitative test for identifying unknown ionic compounds.

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ΔH for the process is -252.3 cal/mol or -1056 j/mol.

A solid salt compound dissociates in liquid water to form an aqueous solution of its constituent ions.

This is a chemical reaction, with the required heat change at constant pressure termed the enthalpy of solution.

If this value is positive, then the final prepared solution will have a lower temperature than the starting pure solvent.

Conversely, a negative enthalpy value results in a solution temperature that is higher than the starting solvent temperature.

It is given that

NaOH (s) → Na (aq) + OH (aq)

mass of NaOH is 16.9 g

mass of water = 70 g

ΔT = 86.6-22.4 °C = 64.2 °C

q = m × Cg × ΔT

q = amount of energy released or absorbed

m = mass

Cg = specific heat capacity

ΔT = change in temperature

n = m ÷ M

n = moles of solute

m = mass of solute

M = molar mass of solute

ΔHsoln = q ÷ n

ΔHsoln = molar enthalpy (heat) of solution

q = amount of energy (heat) released or absorbed

n = moles of solute

Cg= 1 cal/gm/°C

Now substituting the values in the equation

q = m × Cg × ΔT

q = 16.9 * 1 * 64.2

q = 1085 cal

n = m ÷ M

M= 70/18=3.9

n=16.9/3.9

n=4.3

ΔH = q ÷ n

ΔH =1085 /4.3

ΔH= -252.3 cal/mol or -1056 j/mol

Therefore ΔH for the process

NaOH(s) → Na(aq) + OH(aq)

is -252.3 cal/mol or -1056 j/mol

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