Answer: A. To change the potential energy of the reactants.

Explanation:
Catalysts make such a breaking and rebuilding happen more efficiently. They do this by lowering the activation energy for the chemical reaction. Activation energy is the amount of energy needed to allow the chemical reaction to occur. The catalyst just changes the path to the new chemical partnership.

5 0

3 years ago

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You determine that it takes 26.0 mL of base to neutralize a sample of your unknown acid solution. The pH of the solution was 7.8

Lubov Fominskaja [6]

Complete Question

You determine that it takes 26.0 mL of base to neutralize a sample of your unknown acid solution. The pH of the solution was 7.82 when exactly 13 mL of base had been added, you notice that the concentration of the unknown acid was 0.1 M. What is the pKa of your unknown acid?

Answer:

The pK_a value is $pK_a =7.82$

Explanation:

From the question we are told

The volume of base is $V_B = 26.mL = 0.0260L$

The pH of solution is $pH = 7.82$

The concentration of the acid is $C_A = 0.1M$

From the pH we can see that the titration is between a strong base and a weak acid

Let assume that the the volume of acid is $V_A = 18mL= 0.018L$

Generally the concentration of base

$C_B = \frac{C_AV_A}{C_B}$

Substituting value

$C_B = \frac{0.1 * 0.01800}{0.0260}$

$C_B= 0.0692M$

When 13mL of the base is added a buffer is formed

The chemical equation of the reaction is

$HA_{(aq)} + OH^-_{(aq)} --------> A^{+}_{(aq)} + H_2 O_{(l)}$

Now before the reaction the number of mole of base is

$No \ of \ moles[N_B] = C_B * V_B$

Substituting value

$N_B = 0.01300 * 0.0692$

$= 0.0009 \ moles$

Now before the reaction the number of mole of acid is

$No \ of \ moles = C_B * V_B$

Substituting value

$N_A = 0.01800 *0.1$

$= 0.001800 \ moles$

Now after the reaction the number of moles of base is zero i.e has been used up

this mathematically represented as

$N_B ' = N_B - N_B = 0$

The number of moles of acid is

$N_A ' = N_A - N_B$

$= 0.0009\ moles$

The pH of this reaction can be mathematically represented as

$pH = pK_a + log \frac{[base]}{[acid]}$

Substituting values

$7.82 = pK_a +log \frac{0.0009}{0.0009}$

$pK_a =7.82$

8 0

3 years ago

Of the following, ________ should have the highest critical temperature. Of the following, ________ should have the highest crit

3241004551 [841]

Answer:

Explanation:

Critical temperature is the temperature above which gas cannot be liquefied, regardless of the pressure applied.

Critical temperature directly depends on the force of attraction between atoms, it means stronger the force of higher will be the critical temperature. So, from the given options H2 should have the highest critical temperature because of high attractive forces due to H bonding.

Hence, the correct option is H2.

5 0

3 years ago

What is the pH of a 0.28 M solution of ascorbic acid

Nady [450]

Hey there!

Values Ka1 and Ka2 :

Ka1 => 8.0*10⁻⁵

Ka2 => 1.6*10⁻¹²

H2A + H2O -------> H3O⁺ + HA⁻

Ka2 is very less so I am not considering that dissociation.

Now Ka = 8.0*10⁻⁵ = [H3O⁺] [HA⁻] / [H2A]

lets concentration of H3O⁺ = X then above equation will be

8.0*10−5 = [x] [x] / [0.28 -x

8.0*10−5 = x² / [0.28 -x ]

x² + 8.0*10⁻⁵x - 2.24 * 10⁻⁵

solve the quardratic equation

X =0.004693 M

pH = -log[H⁺]

pH = - log [ 0.004693 ]

pH = 2.3285

Hope that helps!

3 0

3 years ago