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3 years ago

14

The Periodic Table is organized into or by _________________. A. All of these B. Groups C. Increasing atomic number D. Propertie

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1 answer:

il63 [147K]3 years ago

7 0

Answer:

My best bet is to go with A. All of these

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The enthalpy of reaction changes somewhat with temperature. Suppose we wish to calculate ΔH for a reaction at a temperature T th

Contact [7]

Answer:

-99.8 kJ

Explanation:

We are given the methodology to answer this question, which is basically Kirchhoff law . We just need to find the heats of formation for the reactants and products and perform the calculations.

The standard heat of reaction is

ΔrHº = ∑ ν x ΔfHº products - ∑ ν x ΔfHº reactants

where ν are the stoichiometric coefficients in the balanced equation, and ΔfHº are the heats of formation at their standard states.

Compound ΔfHº (kJmol⁻¹)

SO₂ -296.8

O₂ 0

SO₃ -395.8

The balanced chemical equation is

SO₂(g) + ½O₂(g) → SO₃(g)

Thus

Δr, 298K Hº( kJmol⁻¹ ) = 1 x (-395.8) - 1 x (-296.8) = -99.0 kJmol⁻¹

Now the heat capacity of reaction will be be given in a similar fashion:

Cp rxn = ∑ ν x Cp of products - ∑ ν x Cp of reactants

where ν is as above the stoichiometric coefficient in the balanced chemical equation.

Cprxn ( JK⁻¹mol⁻¹) = 50.7 - ( 39.9 + 1/2 x 29.4 ) = - 3.90

= -3.90 JK⁻¹mol⁻¹

Finally Δr,500 K Hº = Δr, 298K Hº + CprxnΔT

Δr,500 K Hº = - 99 x 10³ J + (-3.90) JK⁻¹ ( 500 - 298 ) K = -99,787.8

= -99,787.8 J x 1 kJ/1000 J = -99.8 kJ

Notice thie difference is relatively small that is why in some problems it is o.k to assume the change in enthalpy is constant over a temperature range, especially if it is a small range of temperatures.

3 0

3 years ago

What is the number of moles of 60.7 liters of oxygen molecules?

Arturiano [62]

Answer:

2.17 moles of gas.

Explanation:

6 0

3 years ago

Which of the following hypotheses cannot be tested using the scientific method?

lara31 [8.8K]

Answer:

<h2>The bombing of Hiroshima ended World War II.</h2>

Explanation:

[The scientific method includes these steps:

Observation

Hypothesis

Experimentation

Data Analysis

Conclusion]

The first two Hypothesis can be tested with the scientific method, you cannot go back in time and observe or experiment with the bombing of Hiroshima to deduce whether or not it ended World War II.

8 0

3 years ago

In a room full of air, the air is mainly composed of Nitrogen and Oxygen molecules (both at room temperature). Find (to two sign

zloy xaker [14]

Explanation:

Expression for the $v_{rms}$ speed is as follows.

$v_{rms} = \sqrt{\frac{3kT}{M}}$

where, $v_{rms}$ = root mean square speed

k = Boltzmann constant

T = temperature

M = molecular mass

As the molecular weight of oxygen is 0.031 kg/mol and R = 8.314 J/mol K. Hence, we will calculate the value of $v_{rms}$ as follows.

$v_{rms} = \sqrt{\frac{3kT}{M}}$

= $\sqrt{\frac{3 \times 8.314 J/mol K \times 309.02 K}{0.031 kg/mol}}$

= 498.5 m/s

Hence, $v_{rms}$ for oxygen atom is 498.5 m/s.

For nitrogen atom, the molecular weight is 0.028 kg/mol. Hence, we will calculate its $v_{rms}$ speed as follows.

$v_{rms} = \sqrt{\frac{3kT}{M}}$

= $\sqrt{\frac{3 \times 8.314 J/mol K \times 309.92 K}{0.028 kg/mol}}$

= 524.5 m/s

Therefore, $v_{rms}$ speed for nitrogen is 524.5 m/s.

3 0

3 years ago

What is the formula for nickel(IV) hydroxide

MrRissso [65]

Ni(OH)2

Hope this helps

6 0

4 years ago