Module 2 Key Task 3 Chemistry Flashcards
Who was Dmitri Mendeleev?
A Russian chemist who wrote chemistry books and organized elements by increasing atomic weights.
What did Mendeleev leave in his periodic table?
Gaps for elements not known at the time.
How is the modern periodic table arranged?
By atomic (proton) number.
What do elements in the same group of the periodic table have in common?
They have the same number of outer electrons.
What is chromatography?
A technique where the solvent causes samples to separate and travel up paper.
What is the significance of the Rf value in chromatography?
Each substance has a unique Rf value that can be compared to identify it.
Define metallic bonding.
Positive metal ions in a sea of delocalized electrons.
What is the formula to calculate moles?
Moles = mass / Mr.
What does the relative formula mass (Mr) of a substance represent?
The sum of the relative atomic masses of the atoms in the formula.
What is the symbol for relative formula mass?
M.
How do you calculate the relative formula mass of carbon dioxide (CO2)?
C (12) + 2 * O (16) = 44.
What is the mole ratio in the reaction 2Mg : 2MgO?
1:4.
What does the conservation of mass state?
The total mass of reactants equals the total mass of products.
What happens to the total mass if a gas escapes during a reaction?
It appears to decrease.
What happens to the total mass if a gas is gained during a reaction?
It appears to increase.
What is the neutralization reaction between H+ and OH-?
H+ + OH- → H2O.
How do you calculate moles from concentration and volume?
Moles = Concentration x Volume.
What is the formula for the reaction of sodium carbonate with hydrochloric acid?
Na2CO3 + 2HCl → 2NaCl + H2O + CO2.
What is the concentration of HCl if 0.00125 moles of Na2CO3 react?
0.425 mol/dm³.
When are acids fully ionized?
When in aqueous solution.
What type of acids are partially ionized?
Weak acids.
Fill in the blank: Moles = _______ x volume.
Concentration.
What is the importance of consistent results in titration?
They indicate the accuracy of the experiment.
What is the mean titre volume calculated from?
Adding concordant volumes and dividing by the number of values.
