CHEMISTRY HIGH SCHOOL

When water evaporates at constant pressure, the sign of the change in enthalpyA. is negative.
B. is positive.
C. depends on the temperature.
D. depends on the volume of the container.
E. does not exist; that is, the enthalpy change is zero.

Answers

Answer 1
Answer: B. is positive
H20 (l)--> H20 (g)
when that happens, the heat is absorbed into the liquid to change the state of the liquid to gas; therefore, in order to change to a gaseous state, heat must be a reactant. and so enthalpy is increasing

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Given the reaction at 101.3 kPa and 298 K: hydrogen gas + iodine gas -> hydrogen iodide gas This reaction is classified as

Answers

Answer:

Endothermic, because heat is absorbed.

Explanation:
This is classified as a "Formation Reaction"

He accepted value for the density of liquid mercury is 13.5336 g/mL. Four scientists measure the density of liquid mercury in their individual laboratories. The most accurate measurement is made by

Answers

Answer;

-The most accurate measurement is made by;

C. Dr. Smith, who measures 13.54 g/mL.

Explanation;

-The absolute density (how much a given volume of the substance weighs) of mercury is 13593 kilograms per cubic meter. It can also be stated as 13.56 g/cm^3. Accuracy measures the nearness of a calculation to the true value.

-In this case; the measurement by Dr. Smith is near the true value 13.56 g/cm^3, as compared to the measurements by other scientists.That is Dr. Chopra, who measures 13.487 g/mL. Dr. Thompson, who measures 13.5 g/mL. and Dr. Tyler, who measures 13.9336 g/mL.

The most accurate measurement is made by Dr. Smith. He measures this as 13.54 g/ml.

What is the charge of an electron? Positive one

Positive two

Negative one

Negative two

Answers

Answer:

The correct answer is the c = negative one

Explanation:

Hello! Let's solve this!

The electron is a particle that is part of the atom. The atom is also made up of neutrons and protons. Protons have a positive charge and are located in the nucleus. Neutrons have a neutral charge and are also located in the nucleus.

The electron has a negative charge and travels its orbitals around the nucleus.

The correct answer is the c = negative one
The charge on an electron is negative one

Although Rutherford is credited with the famous gold foil scattering experiment, he didn’t actually conduct this experiment himself. It was done by two of his assistants, Hans Geiger and Ernest Marsden. Do you think it was fair to name the experiment after Rutherford while ignoring the other two scientists? Why or why not?

Answers

if he was the primary scientist doing it as he did alot of the heavy lifting then yes its ok, but i also think how the others should also me at least mentioned. Or they could just not name the experiment by a person just so its not too biased

What is true of an Arrhenius acid?a. An Arrhenius acid donates OH- ions.
b. An Arrhenius acid donates H+ ions.
c. An Arrhenius acid accepts H+ ions.
d. An Arrhenius acid accepts OH- ions.

Answers

The substances such as HCl, HNO₃, etc. are Arrhenius acids whereas the substances like NaOH, KOH, etc. are Arrhenius bases. An Arrhenius acid donates H⁺ ions. The correct option is B.

According to Arrhenius, an acid is defined as a substance which dissociates to give hydrogen ions in aqueous solution and base is a substance which dissociates to give hydroxyl ions in aqueous solution.

So the Arrhenius acid ionize in water to give H⁺ ions and Arrhenius base ionize in water to form OH⁻ ions.

Thus Arrhenius acid is option B.

To know more about Arrhenius acid, visit;

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B, An Arrhenius acid donates H+ ions.

Which combination is the best choice to prepare a buffer with a ph of 9.0? which combination is the best choice to prepare a buffer with a of 9.0? nh3; nh4cl (pkb for nh3 is 4.75) hcho2; nacho2 (pka for hcho2 is 3.74) c5h5n; c5h5nhcl (pkb for c5h5n is 8.76) hno2;nano2 (pka for hno2 is 3.33)?

Answers

Answer:

\boxed{\text{NH$_(3)$; NH$_(4)$Cl}}

Explanation:

The best choice to prepare a buffer of pH 9.0 is a conjugate acid/base pair in which the acid has pKₐ = 9.0 ± 1.

Let's examine each of the choices.

A. NH₃/NH₄Cl

For NH₃, = pK_b = 4.75

For NH₄⁺, pKₐ  14.00 - 4.75 = 9.25

B. HCHO₂/NaCHO₂  

For HCHO₂, pKₐ = 3.74

C. C₅H₅N/ C₅H₅NHCl

For C₅H₅N, = pK_b = 8.76

For C₅H₅N⁺, pKₐ  14.00 – 8.76 = 5.21

D. HNO₂/NaNO₂

For HNO₂, pKₐ = 3.33

The only acid with a pKₐ close to 9.0 is the ammonium ion.

The best buffer to prepare a buffer with pH 9.0 is \boxed{\text{NH$_(3)$; NH$_(4)$Cl}}

From the given options, the best combination to prepare a buffer with a PH of 9.0 is given by;

Option 1; NH₃;NH₄Cl

  • A buffer solution is defined as an aqueous solution that consists of a mixture of a weak acid and its conjugate base or mixture of a weak base and its' conjugate acid.

Now, we want to find the best choice to prepare a buffer of pH 9.0. Thus, let us look at each option;

Option 1; NH₃;NH₄Cl

We are given that pK_b for  NH₃ is 4.75

Thus pKₐ for NH₄ is;

NH₄; pKₐ = 14.00 - 4.75

NH₄; pKₐ = 9.25

Option 2; HCHO₂; NaCHO₂  

We are given that pK_a for HCHO₂ is 3.74

HCHO₂; pKₐ = 3.74

Option 3;C₅H₅N; C₅H₅NHCl

We are given that pK_b for C₅H₅N is 8.76

Thus  

For C₅H₅N, = pK_b = 8.76

Thus, pKₐ for C₅H₅N is;

C₅H₅N; pKₐ = 14.00 – 8.76

C₅H₅N; pKₐ = 5.21

Option 4; HNO₂;NaNO₂

We are given pKₐ for HNO₂ as 3.33

HNO₂; pKₐ = 3.33

Looking at all the pKₐ values, the only acid that has a pKₐ close to 9.0 is NH₄ with a pKₐ of 9.25.

In conclusion, the best combination to prepare a buffer with pH of 9.0 is

NH₃;NH₄Cl

Read more at; brainly.com/question/15592723
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