Which level is made up of organisms that break down dead organisms?

A 10.0-ml sample of 0.200 m hydrocyanic acid (hcn) is titrated with 0.0998 m naoh. what is the ph at the equivalence point? for

ryzh [129]

When the titration of HCN with NaOH is:

HCN (aq) + OH- (aq) → CN-(aq) + H2O(l)

So we can see that the molar ratio between HCN: OH-: CN- is 1:1 :1

we need to get number of mmol of HCN = molarity * volume

= 0.2 mmol / mL* 10 mL = 2 mmol

so the number of mmol of NaOH = 2 mmol according to the molar ratio

so, the volume of NaOH = moles/molarity

= 2 mmol / 0.0998mL

= 20 mL

and according to the molar ratio so, moles of CN- = 2 mmol

∴the molarity of CN- = moles / total volume

= 2 mmol / (10mL + 20mL ) = 0.0662 M

when we have the value of PKa = 9.31 and we need to get Pkb

so, Pkb= 14 - Pka

= 14 - 9.31 = 4.69

when Pkb = -㏒Kb

4.69 = -㏒ Kb

∴ Kb = 2 x 10^-5

and when the dissociation reaction of CN- is:

CN-(aq) + H2O(l) ↔ HCN(aq) + OH- (aq)

by using the ICE table:

∴ the initials concentration are:

[CN-] = 0.0662 M

and [HCN] = [OH]- = 0 M

and the equilibrium concentrations are:

[CN-] = (0.0662- X)

[HCN] = [OH-]= X

when Kb expression = [HCN][OH-] /[CN-]

by substitution:

2 x 10^-5 = X^2 / (0.0662 - X)

X = 0.00114

∴[OH-] = X = 0.00114

when POH = -㏒[OH]

= -㏒ 0.00114

POH = 2.94

∴PH = 14 - 2.94 = 11.06

7 0

3 years ago

Enthalpies of reaction calculated from bond energies and from enthalpies of formation are often, but not always, close to each o

jolli1 [7]

The enthalpy change in a reaction is given by-

ΔH°rxn = ∑nΔH°f,products - ∑nΔH°f,reactants

This can be expressed in terms of bond energy as-

ΔH°rxn = BEreactants - BEproducts

Therefore, the calculated bond energy according to the above equation will be-

ΔH°rxn = [ (C-C) + 2(C-O) + 4(C-H) + 2(O-H) ] - [ (C-C) + 2(C-O) + 4(C-H) + 2(O-H) = 0 kJ/mol

<h3>What is enthalpy change?</h3>

Enthalpy change is a measure of the energy emitted or consumed in a reaction. This can be determined using the following equation which involves standard enthalpy of reactant and product formation:

ΔH°rxn = ∑nΔH°f,products - ∑nΔH°f,reactants

<h3>What is bond energy?</h3>

Bond energy is defined as the amount of energy needed to dissociate a mole of molecules into their individual atoms.

Learn more about the Enthalpy Change here:

brainly.com/question/14047927

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6 0

2 years ago

Select the option below that includes the names for all three cubic crystal Bravais lattices. a. complex cubic, face-centered cu

coldgirl [10]

Answer:

The answer is C. Simple cubic, face-centered cubic, body-centered cubic

Explanation:

Simple cubic: Containing one lattice point on each corner of the cube with each atom at the lattice point shared equally between the eight adjacent corners.

Body-centered cubic: having one lattice point in the center of the unit cell in addition to the eight corners. i.e $(\frac{1}{8} * 8 + 1 )$

Face-centered cubic: having lattice points on the faces of the cube giving exactly one half contribution.

7 0

3 years ago

Which is an element? water carbon dioxide air hydrogen?

7nadin3 [17]

Water and carbon dioxide are compounds. Air is a mixture. The element that is listed is hydrogen.

Remember that you can also find elements on a periodic table.

Your answer is hydrogen.

4 0

4 years ago

Read 2 more answers

The periodic table is useful because it is organized to show many patterns and trends. What property shows a decrease moving fro

Morgarella [4.7K]

Answer:

"Electronegativity" decrease moving from the bottom of Group 3 to the top of Group 3

Explanation:

Electronegativity of an element tell us about the ability of an atom to attract the electrons towards the atom. It depends upon the atomic number and also the distance between the valence electrons that is present in the charged nucleus. The electronegativity will increase from left to right while moving in the periodic table. Electronegativity decreases from bottom to top. To measure the electronegativity pauling scale is used.

3 0

3 years ago