Tma04

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TMA04

Question 1

In TMA02 I asked my tutor to give me specific feedback on the learning outcome Ky1. I was advised that I should take a little more care with significant figures and scientific notation. There has not been much emphasis on significant figures and scientific notation in TMA04. However I have taken the advice given by my tutor and broadened it to include attention to detail in all areas dealing with numbers within this assignment especially in questions 2 ai) 2ci) & 3bi).

Question 2

a)
i & ii)

b)
i)

The chemical formula of the compound containing only K+ and SO42- is K2SO4.

ii)

The formula of the simplest possible compound containing only C and I atoms is CI4.

iii)

K2SO4 was formed by ionic bonding and has overall regular/repeated crystal structure, it has a melting point of over 1000oc, ionic compounds like K2SO4 are also often soluble in water. CI4, in contrast, was formed by covalent bonding and has an irregular crystal structure. Molecular compounds have lower melting points and CI4 has a melting point of less than 200oc and is unlikely to be soluble in water. (68)

c)
i)

Magnesium Atomic Number = 12

Magnesium 24 = 12 protons + 12 neutrons (78.6%)
Magnesium 25 = 12 protons + 13 neutrons (10.1%)
Magnesium 26 = 12 protons + 14 neutrons (11.3%)

0.786 x 24 = 18.864 (magnesium 24)
+
0.101 x 25 = 2.525 (magnesium 25)
+
0.113 x 26 = 2.938 (magnesium 26)

= 24.327

Average relative atomic mass of magnesium (to 1 decimal place) = 24.3

ii)

24, 25, 26 indicate how many protons and neutrons (combined) there are in each stable isotope of magnesium. Seeing as an element is defined by the amount of protons we can work out the amount of neutrons by deducting the number of protons from the isotope number. Eg magnesium 26 – 12(protons) = 14 neutrons. Question 3

i)
Lewis Structure

| | |o o |O |o o | | | | |X X | |+ o + o | |X X | | |X | |+ | |+ | |X | | |CL | |C | |CL | | |X | |X | |X | |X | | |X X | | | |X X | |

Structural Formula

[pic]

Both Chloride elements attain the noble gas electronic configuration of Argon Both Oxygen and Carbon elements attain the noble gas electronic configuration of Neon ii)
Dichloromethanone gas reacting with Water

COCl2(g) + H2O (l) ⋄ CO2(g) + HCl(g)

COCl2 (g) + H2O (l) = CO2(g) + 2HCl(g)

Dicholoromethanone gas reacting with Ammonia

COCl2 (g) + NH3 (g) ⋄ NH4Cl (s) + CO(NH2)2 (s)

COCl2 (g) + 4NH3 (g) = 2NH4Cl (s) + CO(NH2)2 (s)

b)

i)

Estimating the overall enthalpy change for Reaction 1.

Step 1: CO (g) + Cl2 ⋄ COCl2
Step 2 : CO (g) + 2Cl ⋄ CO2Cl

[pic](step 1) = 1074 kJ mol-1 + 243 kJ mol-1 = + 1317 kJ mol-1 [pic](step 2) = 2 x (-346 kJ mol-1) + (- 770 kJ mol-1) = - 1462 kJ mol-1

[pic]
= 1317 kJ mol-1 + (-1462 kJ mol-1
= 1317 kJ mol-1 – 1462 kJ mol-1
= -145 kJ mol-1

ii)

The enthalpy change is negative, so the formation of COCl2 is exothermic.

NEEDS DIAGRAM TO BE COMPLETE

c)

i)

Le Chatelier’s principle states that once equilibrium is reached within a system, a change in temperature, pressure or concentration, will force the system to respond in a way that minimises the effect of that change.

Regarding pressure, Le Chatelier’s principle states that an increase in pressure would cause the equilibrium mixture to...
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