pH Flashcards
what does pH measure?
pH is a measure of the hydrogen ion concentration of a solution.
What would you define pH solution that is less than 7?
If the pH of a solution is less than 7 then the solution is acidic.
What would you define pH solution that is greater than 7?
If the pH solution is greater than 7 then the solution is alkaline
What would you define a solution that is equal to 7?
For pH=7 then the solution is neutral.
What does dissociation of water mean?
In pure water a small number of molecules split up (dissociate) into hydrogen ions, H+, and hydroxide ions, OH-. The reactions are reversible: they can go forwards or back.
What is the pH of the dissociation of water reaction in pure water and why?
In pure water, there is an equal concentration of hydrogen ions and hydroxide ions so the pH is equal to 7.
In what solution is the concentration of hydrogen ions greater than the concentration of hydroxide ions?
In acidic solutions, the concentration of hydrogen ions is greater than the concentration of hydroxide ions.
In which solution is the concentration of hydroxide ions greater than the concentration of hydrogen ion?
In alkaline solutions, the concentration of hydroxide ions is greater than the concentration of hydrogen ions.
What do “[ ]” represent?
Concentration of
What is the test for hydrogen?
The test for hydrogen is that it goes “pop” with a lighted splint.
Explain three things that happen when an acidic solution is diluted with water.
The concentration of hydrogen ions decreases
The solution becomes less acidic
The pH rises towards 7
Explain three things that happen when an alkaline solution is diluted with water.
The concentration of hydroxide ions decrease
The solution becomes less alkaline
The pH decreases towards 7
How is the pH affected when an acid or alkali is diluted by a factor of 10?
When an acid or alkali is diluted by a factor of 10 the pH changes by 1.
How are acidic solutions produced?
Soluble non-metal oxides dissolve in water producing acidic solutions. This means that soluble non-metal oxides produce hydrogen ions, H+, in solution.
What are the formula and ionic formulae for hydrochloric acid?
HCL and H+CL-
What are the formula and ionic formulae for sulfuric acid?
H2SO4 or (H+)2SO42-
What are the formula and ionic formulae for Nitric acid?
HNO3 and H+NO3-
How are alkaline solutions formed?
Soluble metal oxides dissolve in water to form alkaline solutions. This means that soluble metal oxides produce hydroxide ions, OH-, in solution.
What is the word equation for the formation of metal hydroxides?
Soluble metal oxide+water–>metal hydroxide.
How do we figure out if a metal oxide is soluble?
To find out if a metal oxide is soluble, check the solubility table on page 8 of the data booklet.
Do all metal oxides dissolve in water and how can we check this?
Not all Metal oxides dissolve in water. You can use the solubility table in the data booklet to check this.
What can affect the pH of the water?
Only the soluble metal oxides affect the pH of the water. They form alkaline solutions so the universal indicator turns blue.
Name two metal oxides that are insoluble in water so do not form alkaline solutions.
Metal oxides like copper oxide and iron oxide are insoluble in water so do not form alkaline solutions.
What are the formula and ionic formulae for Potassium hydroxide?
KOH or K+OH-
What are the formula and ionic formulae for sodium hydroxide?
NaOH or Na+OH-
What are the formula and ionic formulae for Lithium hydroxide?
LiOH or Li+OH-
What are the formula and ionic formulae for calcium hydroxide?
Ca(OH)2 or Ca2+(OH-)2
What are bases?
Metal oxides, Metal hydroxides, Metal carbonates and ammonia are called bases. Bases are substances that can neutralise acids.
What do bases that dissolve in water form?
Bases that dissolve in water form alkaline solutions.
Why does pure water have low conductivity?
Pure water contains a very low concentration of hydrogen ions and hydroxide ions, giving it a very low conductivity.
