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2 years ago

9

Which phrase best describes a chemical reaction? A. mixing two substances B. the combustion of a substance C. forming or breakin

g bonds D. the decomposition of particles

2 answers:

nirvana33 [79]2 years ago

6 0

The answer for the problem is C

Harman [31]2 years ago

4 0

Answer is: C. forming or breaking bonds.

In a chemical reaction, chemical bonds are forming and breaking and this cause the transformation of one group of chemical substances to another

For example synthesis of water from its elements: 2H₂ + O₂ → 2H₂O, nonpolar bonds between hydrogen and oxygen atoms are breaking and new polar bonds are forming between hydrogen and oxygen in molecule of water.

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A sample of a compound of Cl and O reacts with an excess of H2 to give 0.233g of HCl and 0.403g of H2O. Determine the empirical

Vsevolod [243]

Answer:

Cl₂O₇

Explanation:

For the reaction:

ClₓOₙ + H₂ → HCl + H₂O

Moles of HCl and moles of H₂O are:

HCl: 0.233g HCl ₓ (1mol / 36.46g) = 6.39x10⁻³ mol HCl

H₂O: 0.403g H₂O ₓ (1mol / 18.02g) = 2.236x10⁻² mol H₂O

As you can see, moles of HCl are equivalent to moles of Cl in the compound and moles of H₂O are equivalent to moles of O in the compound, that means:

6.39x10⁻³ mol Cl

2.236x10⁻² mol O

Empirical formula is the simplest ratio of atoms presents in a molecule. If Cl is <em>1</em>, Oxygen will be:

2.236x10⁻² mol / 6.39x10⁻³ = <em>3.5</em>

As empirical formula must be given in natural numbers, the empirical formula is:

<em>Cl₂O₇</em>

<em></em>

4 0

2 years ago

Read 2 more answers

Use enthalpies of formation given in appendix c to calculate δh for the reaction br2(g)→2br(g), and use this value to estimate t

Contact [7]

Given reaction represents dissociation of bromine gas to form bromine atoms

Br2(g) ↔ 2Br(g)

The enthalpy of the above reaction is given as:

ΔH = ∑n(products)Δ $H^{0}f(products)$ - ∑n(reactants)Δ $H^{0}f(reactants)$

where n = number of moles

Δ $H^{0}f$ = enthalpy of formation

ΔH = [2*ΔH(Br(g)) - ΔH(Br2(g))] = 2*111.9 - 30.9 = 192.9 kJ/mol

Thus, enthalpy of dissociation is the bond energy of Br-Br = 192.9 kJ/mol

3 0

2 years ago

A 0.380 kg sample of aluminum (with a specific heat of 910.0 J/(kg x K)) is heated to 378 K and then placed in 2.40 kg of water

lbvjy [14]

Answer:

The equilibrium temperature of the system is 276.494 Kelvin.

Explanation:

Let consider the system formed by the sample of aluminium and water as a control mass, in which the sample is cooled and water is heated until thermal equilibrium is reached. The energy process is represented by First Law of Thermodynamics:

$Q_{water} -Q_{sample} = 0$

$Q_{water} = Q_{sample}$

Where:

$Q_{water}$ - Heat received by water, measured in joules.

$Q_{sample}$ - Heat released by the sample of aluminium, measured in joules.

Given that no mass is evaporated, the previous expression is expanded to:

$m_{w}\cdot c_{p,w}\cdot (T-T_{w}) = m_{s}\cdot c_{p,s}\cdot (T_{s}-T)$

Where:

$m_{s}$ , $m_{w}$ - Mass of water and the sample of aluminium, measured in kilograms.

$c_{p,s}$ , $c_{p,w}$ - Specific heats of the sample of aluminium and water, measured in joules per kilogram-Kelvin.

$T_{s}$ , $T_{w}$ - Initial temperatures of the sample of aluminium and water, measured in Kelvin.

$T$ - Temperature which system reaches thermal equilibrium, measured in Kelvin.

The final temperature is now cleared:

$(m_{w}\cdot c_{p,w}+m_{s}\cdot c_{p,s})\cdot T = m_{s}\cdot c_{p,s}\cdot T_{s}+m_{w}\cdot c_{p,w}\cdot T_{w}$

$T = \frac{m_{s}\cdot c_{p,s}\cdot T_{s}+m_{w}\cdot c_{p,w}\cdot T_{w}}{m_{w}\cdot c_{p,w}+m_{s}\cdot c_{p,s}}$

Given that $m_{s} = 0.380\,kg$ , $m_{w} = 2.40\,kg$ , $c_{p,s} = 910\,\frac{J}{kg\cdot K}$ , $c_{p,w} = 4186\,\frac{J}{kg\cdot K}$ , $T_{s} = 378\,K$ and $T_{w} = 273\,K$ , the final temperature of the system is:

$T = \frac{(0.380\,kg)\cdot \left(910\,\frac{J}{kg\cdot K} \right)\cdot (378\,K)+(2.40\,kg)\cdot \left(4186\,\frac{J}{kg\cdot K} \right)\cdot (273\,K)}{(2.40\,kg)\cdot \left(4186\,\frac{J}{kg\cdot K} \right)+(0.380\,kg)\cdot \left(910\,\frac{J}{kg\cdot K} \right)}$

$T = 276.494\,K$

The equilibrium temperature of the system is 276.494 Kelvin.

7 0

2 years ago

At higher elevations, the boiling point of water decreases, due to the decrease in atmospheric pressure. As a result, what could

amid [387]

When we say decrease in boiling point, that means, we achieve boiling at a more lower temperature (lower than 100deg C). This is due to the lower atmospheric pressure. Boiling happens when the vapor pressure is equal the atmospheric pressure. Lower atmospheric pressure takes lower temperature for vapor pressure to equate with the atmospheric pressure. The answer here is letter B.
At higher elevations, it would take longer to hard boil an egg, because there is a lower boiling point, so the egg is boiling in water at a lower temperature.

8 0

2 years ago

Which object(s) formed last in our solar system?

AnnyKZ [126]

Long year ago In space, gravity attracts dust and gas together which created the young solar system. It pulled low-density cloud together to produce initially the solar nebula. These clouds are made of interstellar gas and dust.

The sun formed first from these nebula and dust.

Planetesimals is just a process indicates the formation of Earth and the other planets from concentrations of dust and diffused matter in the solar system.

Inner planets are the planets located closure to the sun in comparison to outer planets. These inner planets are mercury, venus, earth and mars. Thus, 4.5 billion year ago Inner planets formed at last.

5 0

2 years ago

Read 2 more answers