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3 years ago

Use the standard reaction enthalpies given below to determine ΔH°rxn for the following reaction:

Chemistry

1 answer:

Svetlanka [38]3 years ago

7 0

Answer:

(E) -1835 kJ

Explanation:

Use Hess law to answer this question by manipulating algebraically the equations :

Eq .1 PCl5(s) → PCl3(g) + Cl2(g) ΔH°rxn = +157

Eq.2 P4(g) + 6 Cl2(g) → 4 PCl3(g) ΔH°rxn = -1207 kJ

to arrive to the equation in our problem:

P4(g) + 10 Cl2(g) → 4PCl5(s) ΔH°rxn = ?

Notice PCl₅ is the product in our equation and in Eq. 1 is a reactant so we need to reverse it. We need also to multiply it by 4 since that is the number required in the question.

P₄ in equation 2 is a reactant and is also a reactant in our desired equation also it is 1 mol in both. That is telling us to leave it as it is and we can then proceed to add it the the -4 times Eq1 and check everything is right when we add them together.

4PCl3(g) + 4Cl2(g) → 4PCl5(s) ΔH°rxn = -4 x (157 kJ) (change the sign)

P4(g) + 6 Cl2(g) → 4 PCl3(g) ΔH°rxn = -1207 kJ

___________________________________________

P4(g) + 10 Cl2(g) → 4PCl5(s) ΔH°rxn = -4 x (157 kJ) + -1207 kJ

ΔH°rxn = -1835 kJ

See how the PCl3 cancel and the Cl add correctly.

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Why is the mass of the third subatomic particle ignored?

dmitriy555 [2]

Answer: The mass of electrons is mostly ignored because electrons are extremely small compared to neutrons and protons.

Explanation: A proton is about 1,836 times the size of an electron.

On the periodic table, the atomic number for each element can be found. This number is found by measuring the weight of 6.02 x 10^23 atoms of the element in grams. Electrons aren't ignored when finding exact math, but for the sake of simplification high school teachers will generally have you only count the number of protons and neutrons when calculating the mass of atoms.

3 0

1 year ago

imagine that you go into the lab and perform a titration. you measure 40 ml of your analyte and add it to an erlenmeyer flask. t

mote1985 [20]

The Molar concentration of your analyte solution is 1.17 m

<h3>What is titration reaction?</h3>

Titration is a chemical analysis procedure that determines the amount of a sample's ingredient by adding a precisely known amount of another substance to the measured sample, with which the desired constituent reacts in a specific, known proportion.

Make use of the titration formula.

The formula is molarity (M) of the acid x volume (V) of the acid = molarity (M) of the base x volume (V) of the base.

if the titrant and analyte have a 1:1 mole ratio. (Molarity is a measure of a solution's concentration represented as the number of moles of solute per litre of solution.)

26 x 1.8 = 40 x M

M = 26 x1.8 /40

M = 1.17

The Molar concentration of your analyte solution is 1.17 m

To learn more about Titration refer,

brainly.com/question/186765

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5 0

1 year ago

A 25.0 ml sample of 0.150 m hydrazoic acid is titrated with a 0.150 m naoh solution. what is the ph after 15.0 ml of the sodium

babunello [35]

First, we need to calculate moles of hydrazoic acid NH3:

moles NH3 = molarity * volume

= 0.15 m * 0.025 L

= 0.00375 moles

moles NaOH = molarity * volume

= 0.15 m * 0.015 L

= 0.00225 moles

after that we shoul get the total volume = 0.025L + 0.015L

= 0.04 L

So we can get the concentration of NH3 & NaOH by:

∴[NH3] = moles NH3 / total volume

= 0.00375 moles / 0.04 L

= 0.09375 M

∴[NaOH] = moles NaOH / total volume

= 0.00225 moles / 0.04 L

= 0.05625 M

then, when we have the value of Ka of NH3 so we can get the Pka value from:

Pka = -㏒Ka

= - ㏒ 1.9 x10^-5

= 4.7

finally, by using H-H equation we can get PH:

PH = Pka + ㏒[salt/ basic]

PH = 4.7 +㏒[0.05625/0.09375]

∴ PH = 4.48

6 0

3 years ago

Does the following compound contain a polyatomic ion? Na2SO4<br> Yes<br> No

seropon [69]

The answer is yes I believe so.

8 0

3 years ago

Based on your answer in part B, arrange the five elements in order of their reactivity. Drag the most reactive element to the to

amm1812

Answer: Order of the elements from most reactive to least reactive is:

Mg > Zn > Fe > H > Cu

Explanation: Reactivity of the elements is the tendency of the elements to loose or gain electrons with ease.

As, all the given elements are metals, so the metals which will loose electrons easily will be more reactive. To study the reactivity of metals, we use reactivity series.

The metals which are more reactive are placed on the top of the reactivity series and which are less reactive are placed at the bottom.

Hence, the order of the elements from most reactive to least reactive is:

Mg > Zn > Fe > H > Cu

Reactivity series is attached below.

6 0

4 years ago