p2. Reactivity of substances at high temperature
a) Sodium will be unreactive with anything at 10 000° C, including oxygen, (which itself will have decomposed into atoms).
b) Petrol will be very reactive but only to decomposition. It wonít react with oxygen at 10 000° C.
Problem 1 Concentration
Defín : The amount of a substance divided by the volume it occupies.
Explín :Usually in a solution. eg. If 0.1 mol of NaCl (i.e. 5.85 g) is dissolved in 500 mL of solution, the concín is 0.20 mol/L. Concentration is important because the reactivity of a substance usually depends on its concentration. Also, it is often important to know how much of a substance we have. This is easily worked out from the volume and concentration of the solution.
i) SI unit for distance; metre or m, Other units; mile, inch, km, mm, dm, cm, etc.
ii) SI unit for time; second or s. Other units; minute, hour, ks, ms, etc.
a) accín = 3.375 mph/s
b) = 1.5 m.s-2
c) » 0.15 gravities of acceleration.
a) F = m x a = 70 kg x 9.81 m.s-2 = 687 newtons
b) m = F/a = 22N/9.81 m.s-2 = 2.24 kg » 5 lb
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