18.3 Rate-concentration Graphs & Initial Rates
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How can you determine the rate constant from a zero order rate-concentration graph?
rate constant = y intercept y = k[A]0 = k
How can you determine the rate constant from a first order rate-concentration graph?
gradient = rate rate = k[A], y = mx where m = k, since k is constant & x = [A], since [A] is variable
How can you determine the rate constant from a second order rate-concentration graph?
plot a graph of rate against concentration2 transposes curve to straight line gradient of straight line = k
How can you find out the order of a reaction using a clock reaction?
• Measure time taken for visual change to occur • E.g formation of precipitate/colour change • Assuming rate stays fairly constant, instantaneous rate = average rate over whole reaction • Initial rate ∝ 1/t (greater value of t gives slower rate) • Clock reaction repeated several times with different concentrations of reactants • Plot graph of concentration against 1/t, plotting a different graph for each reactant • Order with respect to each reactant is determined based on shape of graph