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3 years ago

What is enthalpy?

Chemistry

2 answers:

White raven [17]3 years ago

7 0

The awnser is A. Idek I looked it up so yeah that’s the awnser

Liula [17]3 years ago

7 0

Answer:

Enthalpy is the heat involved in a reaction.

Explanation:

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A food substance kept at 0Â°C becomes rotten (as determined by a good quantitative test) in 8.3 days. The same food rots in 10.6

ZanzabumX [31]

Answer:

1. 67.2 kJ/mol

Explanation:

Using the derived expression from Arrhenius Equation

$In \ (\frac{k_2}{k_1}) = \frac{E_a}{R}(\frac{T_2-T_1}{T_2*T_1})$

Given that:

time $t_1$ = 8.3 days = (8.3 × 24 ) hours = 199.2 hours

time $t_2$ = 10.6 hours

Temperature $T_1$ = 0° C = (0+273 )K = 273 K

Temperature $T_2$ = 30° C = (30+ 273) = 303 K

Rate = 8.314 J / mol

Since $(\frac{k_2}{k_1}=\frac{t_2}{t_1})$

Then we can rewrite the above expression as:

$In \ (\frac{t_2}{t_1}) = \frac{E_a}{R}(\frac{T_2-T_1}{T_2*T_1})$

$In \ (\frac{199.2}{10.6}) = \frac{E_a}{8.314}(\frac{303-273}{273*303})$

$2.934 = \frac{E_a}{8.314}(\frac{30}{82719})$

$2.934 = \frac{30E_a}{687725.766}$

$30E_a = 2.934 *687725.766$

$E_a = \frac{2.934 *687725.766}{30}$

$E_a =67255.58 \ J/mol$

$E_a =67.2 \ kJ/mol$

7 0

2 years ago

Each molecule of testosterone contains 19 atoms of carbon (plus other atoms). The mass percent of carbon in testosterone is 79.1

Xelga [282]

Answer:

The answer to your question is letter E. 288.4 g/mol

Explanation:

Data

Number of carbons = 19

mass percent of carbon = 79.12

molar mass = ?

Process

1.- Calculate the molar mass of 19 atoms of carbon

Atomic mass of carbon = 12 g

Atomic mass of 19 atoms of carbon = 228 g

2.- Use proportions to calculate the mass of testosterone

228 g --------------- 79.12 %

x -------------- 100 %

x = (228 x 100) / 79.12

Simplify

x = 22800 / 79.12

Molar mass of testosterone = 288.2 g

6 0

3 years ago

A 150.0 mL solution of 2.888 M strontium nitrate is mixed with 200.0 mL of a 3.076 M sodium fluoride solution. Calculate the mas

Lelechka [254]

Answer:

Mass SrF2 produced = 38.63 g SrF2 produced

[Na^+]: = 1.758 M

[NO3^-]: = 1.238 M

[Sr^2+] = 0.3589 M

[F^-] = 2.36*10^-5 M

Explanation:

Step 1: Data given

Volume of 2.888M strontium nitrate = 150.0 mL = 0.150 L

Volume of 3.076 M sodium fluoride = 200.0 mL = 0.200 L

Step 2 : The balanced equation

Sr(NO3)2(aq) + 2NaF(aq) → SrF2(s) + 2NaNO3(aq) → Sr2+ + 2F- + 2

Step 3: Calculate moles strontium nitrate

Moles Sr(NO3)2 = Molarity * volume

Moles Sr(NO3)2 = 2.888 M * 0.150 L

Moles Sr(NO3)2 = 0.4332 moles

Step 4: Calculate moles NaF

Moles NaF = 3.076 M * 0.200 L

Moles NaF = 0.6152 moles

It takes 2 moles F^- to precipitate 1 mole Sr^2+, so F^- is limiting.

Step 5: Calculate limiting reactant

For 1 mol of Sr(NO3)2 we need 2 moles of NaF to produce 1 mol of SrF2 and 2 moles of NaNO3

NaF is the limiting reactant. It will completely be consumed (0.6152 moles).

Sr(NO3)2 is in excess. There will react 0.6152/2 = 0.3076 moles

Moles Sr^2+ precipitated by F^- = 0.3076

There will remain 0.4332 - 0.3076 = 0.1256 moles of Sr(NO3)2

Moles Sr^2+ no precipitated (left over) = 0.1256 moles

Step 6: Calculate moles SrF2

For 1 mol of Sr(NO3)2 we need 2 moles of NaF to produce 1 mol of SrF2 and 2 moles of NaNO3

For 0.6152 moles NaF we have 0.6152/2 = 0.3076 moles of SrF2

Mass SrF2 produced: 0.3076 mol * 125.6 g/mol = 38.63 g SrF2 produced

Step 7: Calculate concentration of [Na+] and [NO3-]

Since both Na^+ and NO3^- are spectator ions, and the final volume is 150 ml + 200 ml = 350 ml (0.350 L), the concentrations of Na^+ and NO3^- can be calculated as follows:

[Na^+]: (200 ml)(3.076 M) = (350 ml)(x M) and x = 1.758 M

[NO3^-]: (150 ml)(2.888 M)(2) = (350 ml)(x M) = 1.238 M

Step 8: Calculate [Sr^2+] and [F^-]

[Sr^2+] = 0.1256 moles/0.350 L = 0.3589 M

To find [F^-], one needs the Ksp for SrF2. There are several values listed in the literature. I am using a value of 2x10^-10.

SrF2(s) <==> Sr^2+(aq) + 2F^-(aq)

Ksp = [Sr^2+][F^-]²

2x10^-10 = (0.3589)(x)²

x² = 5.57*10^-10

x = [F^-] = 2.36*10^-5 M

4 0

3 years ago

What is the predominant intermolecular force in the liquid state of each of these compounds: ammonia (NH3), methane (CH4), and n

MAVERICK [17]

Answer:

The predominant intermolecular force in the liquid state of each of these compounds:

ammonia (NH3)

methane (CH4)

and nitrogen trifluoride (NF3)

Explanation:

The types of intermolecular forces:

1.Hydrogen bonding: It is a weak electrostatic force of attraction that exists between the hydrogen atom and a highly electronegative atom like N,O,F.

2.Dipole-dipole interactions: They exist between the oppositely charged dipoles in a polar covalent molecule.

3. London dispersion forces exist between all the atoms and molecules.

NH3 ammonia consists of intermolecular H-bonding.

Methane has London dispersion forces.

Because both carbon and hydrogen has almost similar electronegativity values.

NF3 has dipole-dipole interactions due to the electronegativity variations between nitrogen and fluorine.

3 0

3 years ago

Why is the sun up sometimes but not other times?

MatroZZZ [7]

Answer: The Sun appears to move across the sky because the Earth rotates on its axis. ... When where you are is pointed toward the Sun, it is day. Then the Earth rotates you away from the Sun, and it is night.

Explanation:

6 0

3 years ago