How Do You Calculate pH for a NaCN and HCN Solution?

NaCN/LIn summary, To find the pH after adding 0.10 mol of NaCN to 100 mL of 0.050 M HCN, apply the Henderson-Hasselbalch Equation with the derived equation for a weak acid and strong base. The resulting solution will form a buffer that can be calculated using the formula pH=pK+log [Salt]/[Acid]. The concentration of NaCN can be calculated using the formula for molarity (moles/volume). The concentration of HCN will remain the same.
  • #1
Giuseppe
42
0
I am stuck on this question...can anyone help?

What is the pH after .10 mol NaCN is added to 100 mL of .050 M of HCN?
(Ka=6.0x10^-19)

I think I have to use the Henderson-Hasselbalch Equation. Is this the right way to take. And if so, how should I go about getting the ion concentration?
 
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  • #2
Apply the derived equation for the Weak Acid and strong base...I guess there is one dervied from that, applying the fact that the HCN will be very less ionized, whereas the NaCN will go and create a strong base thing...NaOH
 
  • #3
Giuseppe,

As you are adding an Acid to its salt, the solution form a buffer which will be basic and can be calculate by using:

pH=pK+log [Salt]/[Acid]

Where [Salt]=Concentration Of NaCN

and [Acid]=Concentration of Acid


Calculate the concentration of salt By using the formula for calculation of molarity if you know the moles and the volume of the solution.
 
  • #4
concentration of HCN will remain the same, for NaCN, .100moles/.1L
 

1. What is an aqueous equilibrium?

An aqueous equilibrium is a state in which the rate of a forward chemical reaction is equal to the rate of its reverse reaction, resulting in a constant concentration of reactants and products in a solution. This can occur in reactions involving substances dissolved in water.

2. How do you calculate the equilibrium constant for an aqueous reaction?

The equilibrium constant (Kc) for an aqueous reaction can be calculated by dividing the concentration of products (raised to the power of their coefficients) by the concentration of reactants (also raised to the power of their coefficients) at equilibrium. This value represents the ratio of the products to reactants at equilibrium and is a measure of the extent of the reaction.

3. What factors can affect the equilibrium constant for an aqueous reaction?

The equilibrium constant for an aqueous reaction can be affected by changes in temperature, pressure, and concentration of reactants and products. Changes in these factors can shift the equilibrium towards the reactants or products, resulting in a change in the equilibrium constant.

4. How do you calculate the pH of an aqueous solution?

The pH of an aqueous solution can be calculated by taking the negative logarithm of the hydrogen ion concentration ([H+]) in moles per liter. This is expressed as pH = -log[H+]. pH values range from 0 to 14, with a pH of 7 considered neutral, below 7 acidic, and above 7 basic.

5. What is the common ion effect in aqueous equilibria?

The common ion effect in aqueous equilibria occurs when a solution contains an ion that is also a reactant in the equilibrium reaction. This extra ion decreases the solubility of the reactant, shifting the equilibrium towards the reactants. This effect is often used in chemical separations and can also be observed in the formation of precipitates in a solution.

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