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2 years ago

A 50.0 g sample of liquid water at 0.0°c ends up as ice at -20.0°c. How much energy is involved in this change.

Chemistry

1 answer:

ANEK [815]2 years ago

5 0

Answer:

-4200J

Explanation:

Since q = mc∆T

where:

m = mass of the substance

c = specific heat capacity of the substance

∆T = change in temperature in Kelvin

but;

the specific heat capacity of water = 4.2J/K/g

Therefore q = 50*4.2*(253-273)

q = -4200J

Note: the negative is only used to indicate heat loss

Hope this helps

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What physical change happens to atoms and molecules in a solution that is strongly heated in a flame? Is there a phase change? I

Charra [1.4K]

When atoms and molecules speed up or slow down, that is a physical change. When they change state from liquid to solid or from gas to liquid, that is a physical change. ... The ions or molecules can still come back together to form the original substance

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2 years ago

he heat of fusion of tetrahydrofuran is . Calculate the change in entropy when of tetrahydrofuran melts at . Be sure your answer

lana [24]

Answer:

$\Delta S=1.8x10^{-3}\frac{kJ}{K}=1.8\frac{J}{K}$

Explanation:

Hello.

In this case, given the heat of fusion of THF to be 8.5 kJ/mol and freezing at -108.5 °C, for the required mass of 5.9 g, we can compute the entropy as:

$\Delta S=\frac{n*\Delta H}{T}$

Whereas n accounts for the moles which are computed below:

$n=5.9g*\frac{1mol}{72g} =0.082mol$

Thus, the entropy turns out:

$\Delta S=\frac{0.0819mol*8.5 kJ/mol}{(-108.5+273.15)K}\\\\\Delta S=1.8x10^{-3}\frac{kJ}{K}=1.8\frac{J}{K}$

Best regards.

3 0

3 years ago

What is the relative atomic mass of a hypothetical element that consists isotopes in the indicated natural abundances

belka [17]

The given question is incomplete. The complete question is:What is the relative atomic mass of a hypothetical element that consists isotopes in the indicated natural abundances.

Isotope mass amu Relative abundance

1 77.9 14.4

2 81.9 14.3

3 85.9 71.3

Express your answer to three significant figures and include the appropriate units.

Answer: 84.2 amu

Explanation:

Mass of isotope 1 = 77.9

% abundance of isotope 1 = 14.4% = $\frac{14.4}{100}=0.144$

Mass of isotope 2 = 81.9

% abundance of isotope 2 = 14.3% = $\frac{14.3}{100}=0.143$

Mass of isotope 3 = 85.9

% abundance of isotope 2 = 71.3% = $\frac{71.3}{100}=0.713$

Formula used for average atomic mass of an element :

$\text{ Average atomic mass of an element}=\sum(\text{atomic mass of an isotopes}\times {{\text { fractional abundance}})$

$A=\sum[(77.9\times 0.144)+(81.9\times 0.143)+(85.9\times 0.713)]$

$A=84.2amu$

Therefore, the average atomic mass of a hypothetical element that consists isotopes in the indicated natural abundances is 84.2 amu

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3 years ago

Why are the molecules of hydrogen chloride gas (hcl) more tightly bound to each other than molecules of oxygen gas (o2)?

Oduvanchick [21]

Answer : If we consider the molecule of oxygen gas which in diatomic state, is bonded to other atom which is of same element this is called as homonuclear.

While in HCl there is a heteronuclear bonding observed because there are two different elements getting involved in the bond formation, also it creates a electrovalent species in itself and makes it more polar. They are creating a dipole moment by separating different charges in the molecule which cause it to get tightly bonded with each other.

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3 years ago

Sulfuric acid (H2SO4) has a molar mass of 98.1 g/mol. How many oxygen atoms are found in 75.0 g of H2SO4?

nekit [7.7K]

Answer:

18.33 ×10²³ atoms

Explanation:

Given data:

Molar mass of sulfuric acid = 98.1 g/mol

Mass of sulfuric acid = 75.0 g

Number of of oxygen atom present = ?

Solution:

Number of moles of sulfuric acid:

Number of moles = mass/molar mass

Number of moles = 75.0 g/ 98.1 g/mol

Number of moles =0.761 mol

one mole of sulfuric acid contain four mole of oxygen atom.

0.761 mol × 4 = 3.044 mol

1 mole = 6.022×10²³ atoms of oxygen

3.044 mol × 6.022×10²³ atoms of oxygen / 1mol

18.33 ×10²³ atoms

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3 years ago