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skelet666 [1.2K]
3 years ago
6

The standard enthalpy change for the following reaction is 873 kJ at 298 K.

Chemistry
1 answer:
Flura [38]3 years ago
8 0

Answer:  - 436.5 kJ.

Explanation:

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation.

The given chemical reaction is,

2KCl(s)\rightarrow 2K(s)+Cl_2(g)  \Delta H_1=873kJ

Now we have to determine the value of \Delta H for the following reaction i.e,

K(s)+\frac{1}{2}Cl_2(g)\rightarrow KCl(s) \Delta H_2=?

According to the Hess’s law, if we divide the reaction by half then the \Delta H will also get halved and on reversing the reaction , the sign of enthlapy changes.

So, the value \Delta H_2 for the reaction will be:

\Delta H_2=\frac{1}{2}\times (-873kJ)

\Delta H_2=-436.5kJ

Hence, the value of \Delta H_2 for the reaction is -436.5 kJ.

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How many grams of H2O are in 34.2 grams of NAOH<br> Need ASAP
Brrunno [24]

Answer:

15.438g H2O

Explanation:

First you need to find the reaction equation:

2H2O+2Na=2NaOH + H2

Hydrogen is a diatomic molecule so it will have a subscript of 2 on the right hand side. From there we can balance the reaction.    

Then we can use stoichiometry:

34.2g NaOH * (1 mol NaOH/39.908g NaOH) * (2 mol H2O/2 mol NaOH) * (18.015g H2O/1 mol H20) = 15.438g H2O

It is important that when you use stoichiometry that all your units cancel out until you only have the unit you want.

3 0
2 years ago
5. A penny weighs about 2.5 g. How many moles of pennies would be required to equal the mass of the moon (7.3x10^24 kg)
schepotkina [342]

5. 1.16 x 10^{26} moles  moles of pennies would be required to equal the mass of the moon.

6. 12.86 moles of ethanol are in a 750 ml bottle of vodka.

Explanation:

5 .Data given:

mass of penny = 2.5 grams

atomic mass of penny = 62.93 grams/mole

moles present in mass of the moon given as = 7.3 x 10^{24} kg

number of moles = \frac{mass}{atomic mass of  1 mole}

number of moles = \frac{2.5}{62.93}

0.039 moles of penny is present in 2.5 grams

0.039 moles of penny in 2.5 grams of it

so, x moles in 7.3 X 10^{27}  grams

\frac{0.039}{2.5} =\frac{x}{7.3 X 10^{27} }

x = 1.16 x 10^{26} moles

so when the mass of the penny given is equal to the mass of moon, number of moles of penny present is 1.1 x 10^{26} .

6.

Given:

vodka = 40% ethanol

volume of vodka bottle = 750 ml

moles of ethanol =?

density of ethanol =0.79 g/ml

atomic mass of ethanol = 46.07 grams/mole

so, from the density of ethanol given we can calculate how much ethanol is present in the solution.

density = \frac{mass}{volume}

density x volume = mass

0.79 x 750 = 592.5 grams

number of moles = \frac{mass}{atomic mass of 1 mole}

number of moles of ethanol = \frac{592.5}{46.07}

                                               = 12.86 moles of ethanol

6 0
3 years ago
When hno2 dissociates in water, which atom is dontaing electrons, allowing water to act as a lewis base?
miss Akunina [59]

Answer to this is O-atom.

Explanation: The Bronsted acid-base theory is the backbone of chemistry. This theory focuses mainly on acids and bases acting as proton donors or proton acceptors.

A^+ + B^- \rightarrow A-B

where A^+ is the Lewis Acid and B^- is the Lewis Base and A-B is the Covalent Bond.

Reaction of dissociation of HNO2 in H_2O is given as:

HNO_2 + H_2O \rightarrow H_3O^+ + NO_2^-

In this reaction O-atom has lone pair in water and therefore it accepts the proton from HNO_2 forming a Lewis Base.

6 0
3 years ago
Speed is the rate of change of position expressed as _____ traveled per unit of time. A. direction B. meter C. displacement D. d
STatiana [176]

Answer:

Distance

Explanation:

7 0
3 years ago
match these items. three-dimensional bonding, hardest natural substance, used as lubricant, nonconductor, weak planar bonds, car
DENIUS [597]

Answer:

1. three-dimensional bonding

Diamond

2. Hardest natural substance

diamond

3. Used as lubricant

Graphite

4. nonconductor

Diamond

5. Weak, planar bonds

Graphite

6.Carbon black or soot

Amorphous

Explanation;

sorry im late, hopefully this can help somebody :)

4 0
2 years ago
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