Why is it important for scientist to be repeatable?

Answer: The enthalpy of the reaction is -1791.31 kJ.

Explanation:

Enthalpy change is the difference between the enthalpies of products and the enthalpies of reactants each multiplied by its stoichiometric coefficients. It is represented by the symbol [tex]Delta H^o_{rxn}[/tex]

[tex]\Delta H^o_{rxn}=\sum (n \times \Delta H^o_{products})-\sum (n \times \Delta H^o_{reactants})[/tex]        .....(1)

For the given chemical reaction:

[tex]3MnO_2(s)+4Al(s)\rightarrow 2Al_2O_3(s)+3Mn(s)[/tex]

The expression for the enthalpy change of the reaction will be:

[tex]\Delta H^o_{rxn}=[(2 \times \Delta H^o_f_{(Al_2O_3(s))}) + (3 \times \Delta H^o_f_{(Mn(s))})] - [(3 \times  \Delta H^o_f_{(MnO_2(s))}) + (4 \times \Delta H^o_f_{(Al(s))})][/tex]

Taking the standard heat of formation values:

[tex]\Delta H^o_f_{(Al_2O_3(s))}=-1675.7kJ/mol\\\Delta H^o_f_{(Al(s))}=0kJ/mol\\\Delta H^o_f_{(MnO_2(s))}=-520.03kJ/mol\\\Delta H^o_f_{(Mn(s))}=0kJ/mol[/tex]

Plugging values in the above expression:

[tex]\Delta H^o_{rxn}=[(2 \times (-1675.7))+(3 \times 0)] - [(3 \times (-520.03))+(4 \times 0)]\\\\\Delta H^o_{rxn}=-1791.31 kJ[/tex]

Hence, the enthalpy of the reaction is -1791.31 kJ.

Answer: B

Explanation: The beetles would be able to use their genetic color to learn how to adapt to the environment and hide from predators.

The statement, that describes the genetic color variation within the beetle population helps them to survive is "the color variation helps them avoid predators."

Genetic variations that can exist in a human population include skin color, hair color, dimples, freckles, and blood type. Human skin tone is a classic changeable characteristic that is regarded to be adaptive. Natural selection can result in major changes in the appearance, behavior, or physiology of individuals in a group in a matter of generations.

Meiosis and sexual reproduction combine various alleles in novel ways to generate genetic variety once new alleles emerge. Because of natural selection, green beetles outnumber red beetles. Color diversity can involve camouflage, and beetles could utilize their genetic color to learn how to adapt to their surroundings and hide from predators.

Because this feature has a genetic foundation, the surviving beetles have progeny of the same hue. Brown coloring, which permits the beetle to have more offspring, becomes increasingly prevalent in the population.

Hence the correct option is B.

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Answer:

16mL

Explanation:

Using the following formula;

CaVa = CbVb

Where;

Where

Ca = concentration/molarity of acid (M)

Va = volume of acid (mL)

Cb = concentration/molarity of base (M)

Vb = volume of base (mL)

According to the information provided in this question;

Ca (HCl) = 2M

Cb (NaOH) = 5M

Va (HCl) = 40mL

Vb (NaOH) = ?

Using CaVa = CbVb

Vb = CaVa/Cb

Vb = 2 × 40/5

Vb = 80/5

Vb = 16mL

Answer:

A. Li= 5.6 g O2= 6.4 g

Explanation:

Lithium oxide, Li2O, is an oxide that contains 2 moles of Li and 1 mole of O per mole of oxide. To solve this question we must find the mass of each atom in the molecule as follows:

2Li = 2*6.941g/mol = 13.882g/mol

O = 1*16g/mol = 16g/mol

Molar mass Li2O:

16+13.882 = 29.882g/mol

The mass of lithium is:

12g * (13.882g/mol / 29.882g/mol) = 5.6g Li

And the mass of oxygen:

12g * (16g/mol / 29.882g/mol) = 6.4g O

Right answer is:

Answer:

425 and 0.28A

Explanation:

Resistance for resistors in parallel

1/ R = 1/250 +1/250

=0.008

R = 1/ 0.008 = 125

Total resistance

R= 125+ 300

=425

...

V= IR

I= V/R

I = 120/425

= 0.28 A

Answer:

Polar

Explanation:

Electronegativity Difference:

0.7 Non-Polar Covalent = 0 0 < Polar Covalent < 2 Ionic (Non-Covalent) ≥ 2

Answer:

(9,5) and (2,1)

Explanation:

From the formula of methane it is clear that one mole of methane has 4hydrogen atoms. So, 37.6×1023 hydrogen atoms are there in 25.0 g of methane. Therefore, 9.4×1023methane molecules and 9.4×1023 hydrogen and 37.6×1023carbon atoms are there in 25.0 g of methane.

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Answer:

im pretty sure its d

Explanation:

OPTION C is the correct answer.

Answer:

2.2)solido

2.3)Sólido cristalino

2.4)Sólido amorfo

Answer:

22.4cm³

Explanation:

Avogadro's law shows that Avogadro's volume is 22.4

Answer:

animals that live in the desert hibernate in winter

am not sure

Answer:

Brick

Explanation:

.................

Answer:

d

Explanation:

pv=nrt

2.5×1.01×10^5×8×10^-3=3×8.31×T

T=

The value of the temperature can be determined by ideal gas law and the temperature will be 0.81 K.

The average kinetic energy of particular atoms and molecules in a system is measured by the temperature.

Ideal gas law explain the relationship between pressure. temperature and volume.

Ideal gas law can be expressed as, PV=nRT.

where, P is pressure. V is volume , n is number of moles ,R is gas constant and T is temperature. It is given that, n= 3 mole, P = 2.5 atm, V = 8 L, T=?, R = 8.31.

Calculation of temperature by using ideal gas law is shown as:

Now, put the values of given data in ideal gas law equation.

T = PV/nR

=2.5×8/3×8.32

= 0.81 K

Therefore, the temperature will be 0.81K.

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Answer:

3.7 atm

General Formulas and Concepts:

Atomic Structure

Gas Laws

Ideal Gas Law: PV = nRT

Explanation:

Step 1: Define

Identify variables

[Given] n = 0.68 mol H

[Given] T = 298 K

[Given] V = 4.5 L

[Given] R = 0.0821 L · atm · mol⁻¹ · K⁻¹

[Solve] P

Step 2: Find Pressure

Step 3: Check

Follow sig fig rules and round. We are given 2 sig figs as our lowest.

3.69705 atm ≈ 3.7 atm

Answer:

Vanished completely.

Explanation:

The atoms of starting substances are transformed into the ending substances because the starting substances mixed with each other and turn into new substances. The starting substances i.e. reactants vanished completely when the ending substances means products are formed completely so we can say that the vanishing of ending substance happened when the ending substances are formed.

Answer:

Sugar was the solute and water was the solvent.

Answer:

Gold and pyrite both have a brilliant metallic luster, but are different tones of yellow. Gold is golden to silvery yellow, whereas pyrite is a pale to medium brassy yellow that sometimes tarnishes.

Explanation:

Answer:

1.89 nol Cu(NO3)2

Explanation:

if you calculate it it will be 1.89

Answer: There are [tex]12.71 \times 10^{-9}[/tex] moles present in [tex]2.11 \times 10^{14}[/tex] molecules of LiBr.

Explanation:

According to the mole concept, there are [tex]6.022 \times 10^{23}[/tex] molecules present in 1 mole of a substance.

Hence, moles in [tex]2.11 \times 10^{14}[/tex] molecules of LiBr are calculated as follows.

[tex]Moles = \frac{2.11 \times 10^{14}}{6.022 \times 10^{23}}\\= 12.71 \times 10^{-9}[/tex]

Thus, we can conclude that there are [tex]12.71 \times 10^{-9}[/tex] moles present in [tex]2.11 \times 10^{14}[/tex] molecules of LiBr.

Answer:

may be the answer is Heat and pressure - melting - cooling

Answer:

Lead can harm production of blood cells and the absorption of calcium needed for strong bones and teeth, muscle movements, and the work of nerves and blood vessels. High lead levels can cause brain and kidney damage.

thanks

Once lead enters the body, it is distributed to organs such as the brain, kidneys, liver and bones. The body stores lead in the teeth and bones where it accumulates over time. Lead stored in bone may be remobilized into the blood during pregnancy, thus exposing the fetus.

Explanation:

Melting is defined as the physical process where a solid state of a substance converts into its liquid state. No change of chemical composition takes place, just the physical state of water is changing.

[tex]\text{Solid}\rightleftharpoons \text{Liquid}[/tex]

There are given carboxylic acids. The melting point of these acids increases to its second group member which is ethanoic acid due to prevalent hydrogen bonding. To break this bonding, a high amount of heat needs to be applied.

But as we move forward, the melting point decreases sharply as an increase in the number of carbon atoms decreases the hydrogen bonding.

Melting point of Formic Acid = [tex]8.3^oC[/tex]

Melting point of Acetic Acid = [tex]16.6^oC[/tex]

Melting point of Propionic Acid = [tex]-21^oC[/tex]

Answer:

773.51495 grams

Explanation:

1 moles KBr to grams = 119.0023 grams

6.5*119.0023 = 773.51495 grams

Answer:

bldg licking no-good also

Answer:

Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen: 2 H2O → 2 H2 + O. Efficient and economical water splitting would be a technological breakthrough that could underpin a hydrogen economy, based on green hydrogen.

Answer:

72.5Kg

Explanation:

that is the procedure above