Question 19 of 30
Why does Hess's law allow you to determine the enthalpy change of a
reaction?
A. It states that the enthalpy of any reaction can be determined using
a bomb calorimeter.
B. It states that the change in enthalpy is independent of the pathway
the reaction takes to get to the products.
C. It states how the equilibrium constant is related to the enthalpy
change.
D. It states that the change in enthalpy depends on the reaction
pathway between the products and the reactants.

Answer:

Cu(NO₃)₂ (aq) + 2 KI (aq) ---> CuI₂ (s) + 2 KNO₃

Explanation:

When writing the reaction with the symbols, you need to take into account the charges of the ions. If he charges on the ions do not balance out in a molecule, they need to be made up for in the form of subscripts. For example, copper (+2) and iodine (-1) have charges which do not balance. Thus, to make the molecule neutral, you need to have two iodine atoms (CuI₂).

The unbalanced equation:

Cu(NO₃)₂ (aq) + KI (aq) ---> CuI₂ (s) + KNO₃

Reactants: 1 copper, 2 nitrate, 1 potassium, 1 iodine

Products: 1 copper, 1 nitrate, 1 potassium, 2 iodine

The balanced equation:

1 Cu(NO₃)₂ (aq) + 2 KI (aq) ---> 1 CuI₂ (s) + 2 KNO₃

Reactants: 1 copper, 2 nitrate, 2 potassium, 2 iodine

Products: 1 copper, 2 nitrate, 2 potassium, 2 iodine

Answer:

Alcohol has considerable toxic effects on the digestive- and cardiovascular systems. Alcoholic beverages are classified as carcinogenic by the International Agency for Research on Cancer and increase the risk of several cancer types.

Explanation:

please mark me brainlist

Alcohol has a fire hazard symbol because it is extremely flammable and can create fires. Too be specific, ethanol alcohol is the flammable substance.

It is important to record all accidents and breakages that occur in the laboratory to prevent them from happening again.

Laboratory accident is defined as the type of accident that occurs in the laboratory leading to harm.

Example of laboratory accidents include the following:

A record of these type of laboratory accidents would hel prevent it's reoccurrence.

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If a snail crawls at a rate of 228.16cm/s, Its speed in miles per hour will 5.10 miles/hour

The rate at which someone or something moves or operates or is able to move or operate.

Snail covers distance in 1 seconds = 228.16 cm

It covers in 60 seconds (1 min) = 228.16 cm x 60 = 6mtrs

It covers in 60 minutes (1 hour) = 228.16 cm x 60 x 60 = 821376 cm

Now, lets convert cm to miles :

As,                    1 cm = 6.21371 x 10⁻⁶ miles

Thus,     821376 cm = 5.10 miles

hence, If a snail crawls at a rate of 228.16cm/s, Its speed in miles per hour will 5.10 miles/hour

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11.48-gram of [tex]KCl0_3[/tex] are needed to produce 6.75 Liters of [tex]O_2[/tex]  gas measured at 1.3 atm pressure and 298 K

The ideal gas law (PV = nRT) relates the macroscopic properties of ideal gases. An ideal gas is a gas in which the particles (a) do not attract or repel one another and (b) take up no space (have no volume).

First, calculate the moles of the gas using the gas law,

PV=nRT, where n is the moles and R is the gas constant. Then divide the given mass by the number of moles to get molar mass.

Given data:

P= 1.3 atm

V= 6.75 Liters

n=?

R= [tex]0.082057338 \;L \;atm \;K^{-1}mol^{-1}[/tex]

T=298 K

Putting value in the given equation:

[tex]\frac{PV}{RT}=n[/tex]

[tex]n= \frac{1.3 \;atm\; X \;6.75 \;L}{0.082057338 \;L \;atm \;K^{-1}mol^{-1} X 298}[/tex]

Moles = 0.3588 moles

Now,

[tex]Moles = \frac{mass}{molar \;mass}[/tex]

[tex]0.3588 moles = \frac{mass}{32}[/tex]

Mass= 11.48 gram

Hence, 11.48-gram of [tex]KCl0_3[/tex] are needed to produce 6.75 Liters of [tex]O_2[/tex] gas measured at 1.3 atm pressure and 298 K

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Answer:

B.

Explanation:

customization requires more material, more machine time which can creates a greater impact on the environment in the sense of pollution (travel by the extra employees, creation of custom materials, increased machine running time). Good luck in your studies. Hope this answers your question in full.

Answer:

b

Explanation:

The empirical formula for a compound composed of 0.0683 mol of carbon ( C ), 0.0341 mol of hydrogen ( H ), and 0.1024 mol of nitrogen ( N ) is  [tex]C_2HN_3[/tex].

An empirical formula tells us the relative ratios of different atoms in a compound.

Given data:

Moles of carbon = 0.0683 mol

Moles of hydrogen = 0.0341 mol

Moles of nitrogen = 0.1024 mol

Dividing each mole using the smallest number that is divided by 0.0341 moles.

We get:

Carbon= 2

Hydrogen=1

Nitrogen=3

The empirical formula for a compound is[tex]C_2HN_3[/tex].

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0.761 mol of [tex]C_7H_{16}[/tex]  would you have if you have 76.36 grams.

A mole is defined as 6.02214076 × [tex]10^{23}[/tex]of some chemical unit, be it atoms, molecules, ions, or others. The mole is a convenient unit to use because of the great number of atoms, molecules, or others in any substance.

Given data:

Mass=76.36 grams

[tex]Moles = \frac{mass}{molar \;mass}[/tex]

[tex]Moles = \frac{76.36 grams}{100.21 g/mol}[/tex]

Moles = 0.761

Hence,  0.761 mol of  [tex]C_7H_{16}[/tex] would you have if you have 76.36 grams.

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D. A change in a substance with no new substances being formed

There are 2 ways a substance can change, physical changes and chemical changes. In all changes, physical or chemical, mass is always conserved.

Physical vs. Chemical

The main difference between a physical and chemical change is the substance at the end.

New substances are only created by chemical changes. Additionally, only chemical changes break apart bonds. Physical changes maintain the same compounds and elements, so bonds are not broken.

Examples of Physical Changes

Physical changes do not change the actual substance, but they can change the form of the substance.

All of these change the state of matter or shape of the substance, but not the chemical makeup.

To convert Scientific Notation to a decimal number, Prescribed steps are to be taken given below.

Scientific notation is a way of writing very large or very small numbers.

A number is written in scientific notation when a number between 1 and 10 is multiplied by a power of 10.

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Answer:

Solution Density of aluminium = 2.7 g/Cm 3 In kg/ m 3 = 27 × 1000 10 =2700 kg/ m 3

Explanation:

Not much of one

Answer:

44.01 g/mol

Explanation:

Carbon dioxide is produced when carbon and oxygen are burned.

To totally burn carbon into carbon dioxide, or CO2, we require one mole of oxygen for every gram of carbon by weight.

or alternatively:

You produce 12+216=44 g of carbon dioxide for every 12 g of carbon.

The weight of CO2 in kg may be calculated if the amount of CO2 in litres is known by converting it to moles and multiplying it by 44.

Answer:

I'm pretty sure the answer is C.

Answer:

Explanation:

Mining:

    Mining is when certain substances are removed from the Earth, usually in large quantities. Mining can occur below the surface of the Earth via tunnels and caves. It can also occur at surface level through methods such as strip mining, which removes huge amounts of soil in the process

Hence,  If the concentration of Acetic acid in vinegar is more than 7%, the limiting reactant is baking soda. If the concentration of Acetic acid in vinegar is less than 7%, the limiting reactant is vinegar.

The limiting reactant (or limiting reagent) is the reactant that gets consumed first in a chemical reaction and therefore limits how much product can be formed.

To solve this problem, it is necessary to know the exact concentration of acetic acid in vinegar, because manufacturers produce many types of vinegar the with different concentrations. Most often, concentration of acetic acid in vinegar ranges from 4% to 8%. In this case, it is possible

to calculate the concentration of vinegar making the assumption that 250 ml of vinegar reacts completely with 24 grams of baking soda.

Acetic acid [tex]CH_3CO_2H[/tex]  reacts with baking soda [tex]NaHCO_3[/tex] according to the equation:

[tex]CH_3CO_2H + NaHCO_3[/tex] → [tex]CH_3CO_2Na + CO_2 + H_2O[/tex]

1. Molar mass of [tex]NaHCO_3[/tex] is 23+1+12+16×3 = 84 g/mol

= [tex]\frac{1 mol \;NaHCO_3}{84 g \;NaHCO_3}[/tex]

= [tex]\frac{24 g \;NaHCO_3 X 1 mol \;NaHCO_3}{84 g \;NaHCO_3}[/tex]

=0.29 mol [tex]NaHCO_3[/tex]

2. From the balanced equation we see that 1 mole of [tex]NaHCO_3[/tex] reacts with 1 mole of [tex]CH_3CO_2H[/tex] , then 0.29 moles of [tex]NaHCO_3[/tex] react with 0.29 moles of [tex]CH_3CO_2H[/tex].

3. Mass of 1 mole of [tex]CH_3CO_2H[/tex] is 12+ 1×3+12+16×2=60 g/mol

= [tex]\frac{0.29 mol \;CH_3CO_2H X \;60 g \;CH_3CO_2H }{1 mol \;CH_3CO_2H}[/tex]

[tex]=17.4 g CH_3CO_2H[/tex]

4. In this step density of vinegar is needed.

Making the assumption that concentration of acetic acid is 7%, we can calculate the mass of acetic acid in 250 ml of vinegar:

Mass of vinegar=Volume × density

= 250 ml ×1.0084 g/ml

=252 g

Mass of acetic acid = mass of vinegar × concentration ÷ 100%

= 252 g × 7% ÷ 100%

= 17.6 g.

17.6 g [tex]CH_3CO_2H[/tex] is very close to 17.4 g [tex]CH_3CO_2H[/tex]. It means, that 250 ml of vinegar with a concentration of acetic acid equal to 7% reacts completely with 24 g of baking soda.

Hence,  If the concentration of Acetic acid in vinegar is more than 7%, the limiting reactant is baking soda. If the concentration of Acetic acid in vinegar is less than 7%, the limiting reactant is vinegar.

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Answer:

9.487 L

Explanation:

argon  mole wt = 39.948 gm/mole

             14.3 gm  / 39.948 gm/mole   = .357965 moles of argon

Use Ideal Gas Law:

PV = n RT     where   R = .082057  L-atm / K-mol

V =  .357965 * .082057 * 436 / 1.35  = 9.487 L

Answer:

= 64584.7176 g

or

= 64.5847 kg

Explanation:

From our question, we have been asked to find the mass of SO₂ containing 6.075 × 10^26 S atoms.

We know that from Avogadro's constant,

1 mole of a substance contains 6.02 x 10²³ ions/atoms/units

Thus,

1 mole => 6.02 x 10²³ atoms

x moles=> 6.075 × 10²⁶ atoms

We cross multiply;

x moles = (6.075 × 10²⁶ x 1)/(6.02 x 10²³)

= 1009.1362 moles

1 mole of SO2 = 64 g

1009.1362 moles = ?

=>

[tex] \frac{1009.1362 \times 64}{1} [/tex]

= 64584.7176 g

= 64.5847 kg

The possible action your solution might contain is amongst [tex]Ag^+[/tex], [tex]Pb^{2+}[/tex], or [tex]Ca^{2+}[/tex].

A solution is a homogeneous mixture of one or more solutes dissolved in a solvent.

NaCl: 20 drops of NaCl were used and no precipitate was formed.

No precipitation formed means the [tex]Cl^-[/tex] cation is soluble in water. From your chart, you might see the halide of [tex]Ag^+[/tex] and [tex]Pb^{2+}[/tex] is insoluble in water, which means they should have formed precipitation but you didn't. This means there's less possibility it contains [tex]Ag^+[/tex] or [tex]Pb^{2+}[/tex], so we are left with only [tex]Ca^{2+}[/tex]. Let's confirm it with the rest.

[tex]Na_2SO_4[/tex] : 20 drops of [tex]Na_2SO_4[/tex] were used yellow precipitate was produced.

Even though all other sulfates form precipitation ( Insoluble in water)

[tex]Na_2CO_3[/tex] : 20 drops of sodium carbonate were used and the silver-blue precipitate was produced.

It seems all of their Carbonate is insoluble in nature. ( which is our case too ).

From the above result, only the reaction with NaCl was deemed to be decisive and it indeed contains [tex]Ca^{2+}[/tex] ions. Means you are correct.

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Answer:

0.12 M

Explanation:

To find the new concentration, you need to (1) find the moles of Solution A (via the molarity equation), then (2) find the moles of Solution B, then (3) combine all of the moles and volumes, and then (4) calculate the new molarity. The final answer should have 2 sig figs to reflect the lowest amount of sig figs in the given values.

Solution A:

7.7 mL / 1,000 = 0.0077 L

Molarity = moles / volume

0.10 M = moles / 0.0077 L

0.00077 = moles

Solution B:

18.3 mL / 1,000 = 0.0183 L

Molarity = moles / volume

0.20 M = moles / 0.0183 L

0.00366 = moles

New Solution:

11.7 mL / 1,000 = 0.0117 L

New Volume = 0.0077 L + 0.0183 L + 0.0117 L

New Volume = 0.0377 L

New Moles = 0.00077 moles + 0.00366 moles

New Moles = 0.00443 moles

Molarity = moles / volume

Molarity = 0.0043 moles / 0.0377 L

Molarity = 0.1175 M = 0.12 M

Answer:

Both metals and non-metals when burnt in oxygen form their oxides. Oxides of metals are basic in nature and oxides of non-metals are acidic in nature.

0.342 x [tex]10^(^1^6^)[/tex])  photons are required to emit 1 joule of energy.

A photon is a particle of light defined as a discrete bundle (or quantum) of electromagnetic (or light) energy.

We need to find the number of photons emitted per second.

So we have E = hc ÷ λ

= (6.6 x [tex]10^-(^3^4^)[/tex]x 3 x [tex]10^8[/tex] m/s) ÷ 6.78 x [tex]10^(^-^7^)[/tex]nm

= 2.92 x [tex]10^(^-^1^9^)[/tex]Joules

Now number of photons per second = I / E (I = intensity)

= 1 x [tex]10^(^-^3^)[/tex] joule / sec ÷ 2.92 x [tex]10^(^-^1^9^)[/tex]joule

= 0.342 x[tex]10^(^1^6^)[/tex]

Hence, 0.342 x [tex]10^(^1^6^)[/tex])  photons are required to emit 1 joule of energy.

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Answer:

4.43 g Fe

Explanation:

To find the mass of iron, you need to (1) convert grams Al to moles Al (via molar mass), then (2) convert moles Al to moles Fe (via mole-to-mole ratio from reaction coefficients), and then (3) convert moles Fe to grams Fe (via molar mass). It is important to arrange the conversions/ratios in a way that allows for the cancellation of units (the desired unit should be in the numerator). The final answer should have 3 sig figs because the given value (2.14) has 3 sig figs.

Molar Mass (Al): 26.982 g/mol

2 Al(s) + Fe₂O₃ --->  2 Fe(s) + Al₂O₃(s)

Molar Mass (Fe): 55.845 g/mol

 2.14 g Al           1 mole              2 moles Fe           55.845 g
----------------  x  -----------------  x  --------------------  x  ------------------  =  4.43 g Fe
                         26.982 g           2 moles Al             1 mole

Aluminum reacts with ferric oxide to produce iron by the thermite reaction. The mass of the iron metal that will be formed by the chemical reaction is 4.43 g Fe.

Limiting reagent has been described as reactions that are present in lesser amounts than the other reactant in the reaction that determines the amount of formation of the products and are never left in a reaction.

The balanced thermite reaction is given as:

2 Al(s) + Fe₂O₃ → 2 Fe(s) + Al₂O₃(s)

Molar mass of aluminium = 26.982 g/mol

Molar Mass of iron= 55.845 g/mol

Mass of aluminium (Al) = 2.14 grams

Here, according to the reaction 2 moles of Aluminum are needed to produce 2 moles of iron (Fe).

Moles of aluminum is calculated as:

Moles = mass ÷ molar mass

n = 2.14 ÷ 26.982

= 0.079 mol

As aluminum is the limiting reagent, it determines the formation of iron as:

2 mol Al = 2 mol Fe

0.079 mol Al = 0.079 mol Fe

Mass of iron is calculated as:

Mass = moles × molar mass

mass = 0.079 × 55.845 g/mol

= 4.411 grams

Therefore, 4.43 g Fe will be produced from 2.14 gm Al.

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Answer:

6PbO +O2 --> 2Pb3O4

Explanation:

The question is incomplete I assume it is

PbO + 02 - Pb304

The following is an insoluble compound that is likely to be produced by the reaction below CaSO4 + PbI- CaI + PbSO4. The PbSO4 will be insoluble as The sulfates are insoluble in water besides for the sulfates of calcium, barium, mercury, and lead.

Lead sulphate ($PbS$) is insoluble in water due to the fact water's dipole electricity is simply too vulnerable to shy away the ions (each anion and cations) from the sturdy crystals of lead sulphate.Lead sulfate seems as a white crystalline solid. Insoluble in water and sinks in water. Contact might also additionally aggravate skin, eyes, and mucous membrane.

Thus, PbSO4 is insoluble. In PbSO4 , the electricity of the dipole is vulnerable to interrupting the anionic and cationic bond. So, PbSO4 stays insoluble in solution.

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180.189 g was the mass of the zinc sample with a specific heat of zinc is 0.390 j/g°C.

The specific heat capacity is defined as the quantity of heat (J) absorbed per unit mass (kg) of the material when its temperature increases 1 K (or 1 °C), and its units are J/(kg K) or J/(kg °C).

Using specific heat capacity formula here:

[tex]C_{Zn}[/tex] × [tex]m_{Zn}[/tex]×  Δ[tex]T_{Zn}[/tex] = [tex]C_{H_2O}[/tex]× [tex]m_{H_2O}[/tex] ×  Δ[tex]T_{H_2O}[/tex]

0.390J/g°C × [tex]m_{Zn}[/tex] ×77.4ºC = 4.184J/g°C×  65.0g ×  20.00ºC.

[tex]m_{Zn}[/tex] = 180.189 g

Hence, 180.189 g was the mass of the zinc sample.

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Answer: Decide whether they have designed the best possible product.

The concentration of sodium chloride in the solution is 5.72% (weight/volume percent).

Weight/volume percent concentration (w/v) expresses the amount of solute (in grams) dissolved in a given volume of solution (in milliliters). Specifically, it is defined as the weight of the solute divided by the volume of the solution, multiplied by 100.

To calculate the weight/volume percent concentration, we need to determine the mass of NaCl per volume of the solution.

First, we need to convert the volume of the solution from milliliters (mL) to liters (L):

67.8 mL = 0.0678 L

Next, we calculate the concentration of NaCl in grams per liter (g/L):

Concentration = Mass of solute ÷ Volume of solution

Concentration = 3.88 g ÷ 0.0678 L

Concentration = 57.2 g/L

Finally, we convert the concentration to weight/volume percent by multiplying by 100:

Weight/volume percent = Concentration x 100

Weight/volume percent = 57.2 g/L x 100

Weight/volume percent = 5.72%

Therefore, the concentration of NaCl in the solution is 5.72% (weight/volume percent).

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Answer:

It's a Ionic compound

Explanation:

To tell if CaO (Calcium oxide) is ionic or covalent (also called molecular) we look at the Periodic Table that and see that Ca is a metal and O is a non-metal. When we have a metal and a non-metal the compound is usually considered ionic.

Because we have a metal and non-metal in CaO there will be a difference in electronegativity between the metal and non-metal. This difference results in an electron(s) being transferred from the metal (lower electronegativity) to the non-metal (higher electronegativity). The results in the metal becoming a postitive ion and the non-metal a negative ion. The two opposite charges are attracted and form the ionic bond between atoms in Calcium oxide.