El fosfato trisódico (Na3 PO4) se vende en las ferreterías como FTS y se usa como agente limpiad

step 1 Trisodium phosphate, TSP, is available in hardware stores. It has a chemical formula in E3, P .O

El fosfato trisódico (Na3 PO4) se vende en las ferreterías...

Key Concepts

Molarity and Stoichiometry

Molarity is a unit of concentration defined as moles of solute per liter of solution. Converting a given mass of a compound into moles using its molar mass is a basic stoichiometric calculation that is essential for determining the concentration of species in solution. This concept underpins many quantitative analyses in solution chemistry, including pH calculations.

Interplay of Water Autoprotolysis (Kw)

The ion product of water (Kw) is a constant at a given temperature, representing the equilibrium between hydrogen ions and hydroxide ions in water. It plays a crucial role in linking the concentrations of H+ and OH? in a solution. Understanding Kw is essential when computing pH from a known hydroxide ion concentration and for establishing the relationship between pH and pOH.

Salt Hydrolysis

Salt hydrolysis occurs when a salt derived from a weak acid and a strong base reacts with water. In these reactions, the anion of the salt can react with water to produce hydroxide ions, making the solution basic. This concept is crucial for understanding why certain salts, once dissolved, yield solutions with elevated pH values.

pH and pOH Relationship

pH is a measure of the hydrogen ion concentration in a solution, while pOH measures the hydroxide ion concentration. They are related through the equation pH + pOH = 14 at 25°C. This relationship allows one to determine the acidity or basicity of a solution by calculating one value from the other when the concentration of hydroxide or hydrogen ions is known.

Chemical Equilibrium and Hydrolysis Reactions

Many reactions in solution, including the hydrolysis of anions, reach an equilibrium state where the forward and reverse reaction rates are equal. The equilibrium constant for these reactions quantifies the extent to which the reactants are converted to products. Calculating the hydroxide ion concentration often requires setting up an equilibrium expression and solving for concentrations, which is a fundamental exercise in chemical equilibrium.

Transcript

00:01 Trisodium phosphate, tsp, is available in hardware stores.

00:06 It has a chemical formula in e3, p .o4, and it's used as a cleaning agent.

00:13 The label warns that this is very basic and likely uses the words caustic or alkaline.

00:33 We are asked to find the ph with 35 .0 grams of tsp in one liter of solution.

00:48 So this will be pretty straightforward.

00:55 Let's first figure out the molarity, and we'll do that by taking our moles per liter.

01:09 We'll have to convert our moles, which is 35 .0 grams.

01:15 We only have one substance, so this is substance.

01:17 I'm going to leave it off to conserve space.

01:23 Multiply that by one mole, and the molar mass is 163 .9 grams.

01:30 I just cheat and look that up, dividing that by 1 .00 liters, equals 0 .2135.

01:40 And that will be to correct sig figs i go to three and this will be my p .04 concentration, p .o4 3 minus concentration.

01:56 Go there.

02:33 And this was, there it was, i couldn't find it, oh let's just go 214, that's good enough.

03:11 And this will be 0 .214 minus x.

03:14 So here are my three concentrations.

03:20 To find our kb, let's put some brighter colors here...

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