Quantative Analysis Flashcards
What is the mass of 0.1 mole of sulfur dioxide.
(Oxygen = 16) (sulfur = 32)
16 x 2 = 32
32 + 32 = 64
64 x 0.1 = 6.4
What mass of magnesium oxide should be formed, (theoretical yield) when 2.4g of Mg reacts with 1.6g of O
2.4 + 1.6
4 grams
Calculate the percentage yield when theoretical yield is 4g and the theoretical yield is 3.3g.
3.3 ÷ 4 = 0.825
0.825 × 100 = 82.5
82.5%
What is the formula for atom economy?
Atom economy = (rfm of the useful product ÷ sum of rfm of all the reactants) ×100
What is the atom economy for making ammonia using nitrogen and hydrogen? N² + H⁶ = 2(NH³)
N² = 28
H⁶ = 6
NH³ = 17 17 × 2 = 34
Useful product equals 34
All reactants equal 34
34 ÷ 34 =1 1×100 = 100%
100%
How many moles are there in 66g of carbon dioxide. CO² C = 12 O = 16
12 + (16 ×2) = 44
66g ÷ 44 = 1.5 moles
What is the formula for concentration?
Mass of solute(g) ÷ volume of solution(dm³)
= concentration (g dm-3)
Dm is to the power of neg 3
25g of sulafte is dissolved in 500cm³ of water. What is the concentration in g dm-3
500 ÷ 1000 = 0.5 dm³
25 ÷ 0.5 = 50 gdm -3
What mass of sodium chloride is in 300cm³ of solution with a concentration of 12g dm-3?
300 ÷ 1000 = 0.3 dm³
12 × 0.3 = 3.6
3.6g of sodium chloride
What is avogadro’s constant?
6.02 x10²³
Calculate the number of moles in 90g of water. Rfm = 18
90 ÷ 18 = 5
5 moles
Calculate the mass of 0.200 moles of potassium bromide. Rfm of KBr = 119
119 x 0.2 = 23.8 moles
What mass of sodium hydroxide is contained in 200cm³ of a 55g dm-³ solution?
200 ÷ 1000 = 0.2 dm³
0.2 × 55 = 16.5
11g
What is the difference between chemical and empirical formulas?
Chemical formulas state the actual amount of atom of each element.
Empirical formulas state the smallest whole number ratio of the atoms
A sample of hydrocarbon contains 36g of carbon and 6g of hydrogen. Work out the empirical formula.
C = 12
H = 1
36g ÷ 12 = 3
3 moles of carbon
6 ÷ 1 = 6
6 moles of hydrogen
3 ÷ 3 = 1 Carbon
6 ÷ 3 = 2 Hydrogen
CH²
practical to find metal ions present
(flame test)
light Bunsen to blue flame (open air hole )
clean loop with HCl
pick small sample of test using loop
hold the loop with smample to edge of flame and observe colour
how would u make the flame test more accurate
and how
by using a flame photomerty
.sensitivity- can detect smaller amounts
.accuracy-can give value closer to he true value
speed
test for metal ions
what colour flame would you see for each ion present
lithium Li+ red
sodium Na+ yellow
potassium k+ lilac
calcium2+ Orange-red
copper2+ blue-green
What is a mole?
1 mole is 6.02 x10²³ particles
1 moles of Oxygen gas(o²) weighs 32g
1 mole is also equal to the ram of a substance
To work out moles you do mass(g) divided by ram.
72 grams of oxygen gas would be 2 moles
72 grams of oxygen(O) would be 4 moles
8.1g of zinc oxide reacts with 0.3g of carbon. The balanced chemical reaction is
2 ZnO + C -> CO² + 2 Zn
First work out moles.
Moles of zinc = 8.1 ÷ 81(ram) = 0.1 mol
Moles of Carbon = 0.3 ÷ 12 = 0.025 mol
The ratio of moles in terms of mass is 4 to 1. The ratio of moles needed for the reaction is 2 to 1. There is an excess amount of Zinc oxide.
Carbon is the limiting reactant
how to work out concentration
using volume of solution (g dm3)
concentration (g dm3-) / volume of solution (dm-3)
how to work out concentration with moles
(mol dm3-)
moles(mol)/ volume (dm3)
how to work out concentration when given the mr of solute (mol dm3-)
conc/mr
concentraion when given mass
(g dem-3)
mass/volume
how to work out amount (mol)
volume (dm3) / molar volume (24)
