c4 - chemical calculations

Question 1

what do we use as a standard atom to compare the masses of all other atoms?

Answer 1

12
C
6

Question 2

what are relative atomic masses?

Answer 2

• they take into account the proportions of any isotopes of the element found naturally
• it is the mean relative mass of an element conpared with the standard carbon atom so not always a whole number

Question 3

how do you calculate relative atomic mass?

Answer 3

isotope mass x isotope abundance / 100

Question 4

define relative formula mass

Answer 4

• same as relative molecular mass
• adding up relative atomic mass of atoms in formula

Question 5

what is a mole?

Answer 5

• chemical amounts measures in moles (mol)
• one mole of a substance is the relative atomic mass or relative formula mass of the substance expressed in grams

Question 6

define avrogadro’s constant

Answer 6

• a mole of any substance always contains the same number of atoms, molecules or ions
• this number is avrogadro’s constant: 6.02 x 10^23

Question 7

give the two equations to calculate number of moles

Answer 7

1) no. of moles = mass (g) / Ar
2) no. of moles = mass (g) / Mr

Question 8

define concentration

Answer 8

measured in grams per decimetre cubed

Question 9

give the concentration equation when working in dm^3

Answer 9

conc (g/dm^3) = mass of solute (g) / vol. of solute (dm^3)

Question 10

give the concentration equation when working in cm^3

Answer 10

mass of solute (g) / vol. of solute (cmgive the concentration equation when working in dm^3) x 100