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3 years ago

74. Which two temperatures are identical for the same substance?

Chemistry

1 answer:

AURORKA [14]3 years ago

4 0

Answer:

(A) melting point, freezing point.

Explanation:

For the same substance: when matter is transitioning from solid to liquid (melting) or liquid to solid (freezing), its temperature is fixed at the melting/freezing point, which is the same temperature.

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Select the true statements.

Natasha2012 [34]

Answer:

A) and D)

Explanation:

A) BF 3 has a trigonal planar shape

TRUE.

BF₃ has three bonding pairs and no lone pairs. According to VSEPR theory, it is an AX₃ molecule with trigonal planar geometry.

B) Molecules with three outer atoms always have a trigonal planar shape.

False

NH₃ has three outer atoms but a trigonal pyramidal shape.

C) NH₃ has a trigonal planar shape

False.

NH₃ has three bonding pairs and one lone pair. According to VSEPR theory, it is an AX₃E molecule with trigonal bipyramidal geometry.

D) Trigonal planar molecules have three regions of high-electron density around the central atom

TRUE

The regions of high-electron density are the three bonding pairs.

8 0

4 years ago

What types of change if any can reach equilibrium

Lina20 [59]

A chemical change. ....

5 0

3 years ago

30.) Use Percentages: According to the data in table above, what percentage of the energy used in the United States comes from f

STatiana [176]

Answer:

im no expert i believe 42

hope it helps

Explanation:

4 0

3 years ago

Read 2 more answers

Calculate the percentage by mass of the indicated element in the following compounds. Hydrogen in ascorbic acid, HC6H7O6, also k

Scorpion4ik [409]

Answer: The mass percent of hydrogen in ascorbic acid is 4.5 %

Explanation:

In $C_6H_8O_6$ , there are 6 carbon atoms, 8 hydrogen atoms and 6 oxygen atoms.

To calculate the mass percent of element in a given compound, we use the formula:

$\text{Mass percent of hydrogen}=\frac{\text{Mass of hydrogen}}{\text{Molar mass of ascorbic acid}}\times 100$

Mass of hydrogen = $8\times 1g/mol=8g$

Molar Mass of ascorbic acid = $6\times 12g/mol+8\times 1g/mol+6\times 16g/mol=176g$

Putting values in above equation, we get:

$\text{Mass percent of hydrogen}=\frac{8g}{176}\times 100=4.5\%$

Hence, the mass percent of of hydrogen in ascorbic acid is 4.5 %.

8 0

3 years ago

The heat of combustion of propane, C3H8 (g) is -2057 kJ/mol. What would be the enthalpy change if enough propane was burned to g

Digiron [165]

Considering the reaction stoichiometry, the enthalpy change if enough propane was burned to give off 12 moles of carbon dioxide gas is 8228 kJ.

The balanced reaction is:

C₃H₈(g) + 5 O₂(g) → 3 CO₂(g) + 4 H₂O(l)

The heat of combustion of propane, C₃H₈, is -2057 kJ/mol. This is, 2057 kJ is released for every 1 mol C₃H₈.

So to determine the enthalpy change if enough propane was burned to emit 12 moles of carbon dioxide, you must take into account the stoichiometry of the reaction.

By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:

C₃H₈: 1 mole
O₂: 5 moles
CO₂: 3 moles
H₂O: 4 moles

Then you can apply the following rule of three: if by stoichiometry 3 moles of CO₂ are produced by 1 mole of C₃H₈, 12 moles of CO₂ are produced by how many moles of C₃H₈?

$amount of moles of C_{3} H_{8} =\frac{12 moles of CO_{2}x1 mole of C_{3} H_{8} }{3 moles of CO_{2}}$

amount of moles of C₃H₈= 4 moles

So to determine the enthalpy change, you can apply the following rule of three: If for each mole of C₃H₈ 2057 kJ are released, for 4 moles of C₃H₈ how much heat is released?

$Heat released=\frac{4 molesx2057 kJ}{1 mole}$

Heat released= 8228 kJ

The enthalpy change if enough propane was burned to give off 12 moles of carbon dioxide gas is 8228 kJ.

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5 0

3 years ago