Chemistry Unit 1
Write an equation to show the thermal decomposition of barium nitrate.
2Ba(NO3)2(s) --> 2BaO(s) + 4NO2(g) + O2(g)
The empirical formula of a compound is CHO and its relative molecular mass has the value 174. Determine the molecular formula of this compound.
CHO = 29 174/29 = 6 C6H6O6
What are the different types of bonding?
Covalent, ionic and metallic
A student added some dilute sulphuric acid is added to a solution of sodium hydroxide in a test-tube. Write an ionic equation for the reaction that occurred.
H+(aq) + OH-(aq) --> H2O(l)
Are metallic substances soluble or insoluble?
Insoluble
Are both magnesium sulphate and barium sulphate soluble in water?
Only Magnesium sulphate
Explain briefly the process by which a sample is ionised in a mass spectrometer.
The atom or molecule is ionised by knocking electrons off to give a positive ion.
After ionisation and before deflection what happens to the ions?
The ions are accelerated so that they all have the same kinetic energy.
Define Mass Number.
The number of protons and electrons in an atom.
Define Atomic Number.
The number of protons in an atom.
Why are Chromium and Copper exceptions?
To achieve a more stable arrangement of lower energy one of the 4s electrons is promoted into the 3d to give 6 unpaired electrons with lower repulsion.
100 cm3 of a standard solution of Na2CO3 was produced by dissolving 0.537 g of Na2CO3 in water in a volumetric flask. Calculate the concentration, in mol dm-3, of the Na2CO3 solution.
0.537 g in 100 cm3 to 5.37 g dm-3 5.37/106 = 0.0507 mol dm-3
What 3 things are needed to make results more accurate?
1)Repeats 2)Removing anomalies 3)Averages
Calculate the number of moles of gas present in 2.6 dm3 at a pressure of 1.01 x 105 Pa and 300 K using the ideal gas equation.
2.6 dm3 = 0.0026 m3 0.0026 x 1.01 x 105 = n x 8.314 x 300 n = 0.0026 x 1.01 x 105 / 8.314 x 300 n = 0.105 moles
Calculate the empirical formula of an oxide of nitrogen which contains 25.9% of nitrogen by mass.
% O = 100 - 25.9 = 74.1 N : O = 1 : 2.5 N2O5
What is the electronic configuration for Gallium?
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p1
What are the two types of covalent bonding?
Simple molecular and Macromolecular
Why is it important to re-weigh the weighing boat after pouring out the substance?
To ensure that none of the substance is lost or to account for any lost substance.
What does it mean to get concordant results?
To have results that are 0.1 below or above each other
What is the electronic abbreviation for Sodium?
[Ne] 3s1
What is the electronic configuration for Li+?
1s2
Define the term isotope.
A form of an element with the same number of protons but a different number of neutrons.
Which groups are known as the 's' blocks?
Groups 1&2
Which groups are known as the 'p' blocks?
Groups 3-8/0
What is the strongest type of intermolecular force?
Hydrogen bonding
What is the relative mass of protons, neutrons and electrons? a)1,0,1 b)1,1,0 c)0,1,0
b.
What is the relative charge of protons, neutrons and electrons? a)+1,+1,0 b)-1,+1,0 c)+1,0,-1
c.
A mass spectrometer measures the relative abundance of ions with different values of m/z. Explain the meanings of the terms 'm' and 'z'.
m= mass. z=charge.
Lead(II) nitrate may be produced by the reaction between nitric acid and lead(II) oxide as shown by the equation below. PbO + 2HNO3 → Pb(NO3 )2 + H2O. An excess of lead(II) oxide was allowed to react with 175 cm3 of 1.50 mol dm-3 nitric acid. Calculate the maximum mass of lead(II) nitrate which could be obtained from this reaction.
moles HNO3 = 175 × 10-3 × 1.5 = 0.2625 mol moles Pb(NO3)2 = ½ × 0.2625 = 0.131mol Mr Pb(NO3)2 = 331.2 mass Pb(NO3)2 = 331.2 × 0.131= 43.3g
What are the 4 types of crystal structure?
Ionic, metallic, molecular and macromolecular
State the trend in reactivity down Group 2 and explain it.
As you go down the group, the number of electron shells between the outermost electrons and the nucleus increases. This means the hold the nucleus has on these outer electrons decreases. Because it has less hold on these electrons, it takes less energy to release them from the atom. So reactivity increases.
Are polar molecules symmetrical or asymmetrical?
Asymmetrical
Write an equation to show the reaction of barium metal with water.
Ba(s) + 2H2O(aq) --> Ba(OH)2(aq) + H2(g)
