rate equations questions
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Use evidence from the rate equation to explain why Step 1 is the rate determining step
Step 1 includes CH3COCH3 and OH- and these are also in the rate equation OR Step 1 contains all the species in the rate equation
Suggest why a loose cotton wool plug is placed in the neck of the flask, instead of leaving the flask open or inserting a bung.
M1 (Instead of leaving the flask open) to avoid acid/solution/liquid escaping OR to avoid (acid/solution/liquid) splashing/spraying/spitting (out). M2 (Instead of inserting a bung) to allow gas/CO2 to escape
20 g of large marble chips is a large excess of calcium carbonate. Suggest why using a large excess of calcium carbonate means that the rate is only affected by the changing concentration of the hydrochloric acid.
So that surface area/mass/amount stays (approx./effectively) constant
The mass of carbon dioxide produced in time t is equal to mt. The total mass of CO2 produced during the reaction is equal to mtotal. Explain why (mtotal – mt) is proportional to the concentration of hydrochloric acid remaining in the flask at time t.
M1 mt/mass of CO2 produced in time t is proportional to the (amount/concentration of) HCl that has reacted (at time t) M2 mtotal/total mass of CO2 produced is proportional to the total (amount/concentration of) HCl that has reacted/was present initially (therefore mtotal - mt is proportional to (amount/conc of) HCl present at time t)
State how the graph in Figure 2 confirms that the rate equation for this reaction is Rate = k[HCl] (The line was straight going diagonally to the right )
Straight line AND through origin
A suggested mechanism for the reaction is shown. Step 1 B + H+ → BH+ Step 2 BH+ + B → B2H+ Step 3 B2H+ + A → C + D Deduce the rate-determining step for this reaction. Give a reason for your answer.
M1 Step 2 M2 (By the end of step 2) 1 × H+ and 2 × B have been used
re arraneg the arrhenius equation for whatever
Explain why the rate of reaction is faster at T2
M5 At T2 (many) more particles have E≥Ea
Give the name of CH3CH2COCH2I
1-iodobutan-2-one Allow 1-iodo
Suggest an observation used to judge when all the iodine had reacted.
Brown colour removed
Describe and explain the shape of the graph above. go to question 6d
As T increases rate (1/t) increases OR time for completion decreases M1 Exponentially OR By a greater/ increasing factor Many more particles have E ≥ Ea
Hydrogen peroxide solution decomposes to form water and oxygen. 2 H2O2(aq) → 2 H2O(l) + O2(g) Explain why the reaction is fastest at the start.
M1 Higher/est concentration of / more H2O2 / particles / molecules / reactants 1 M2 More frequent successful collisions
Read
When asked to workout the Ea froma grpah find the gradient from 8sing the values given from table multiply that number by 8.31 then divide by 1000 multipky instead of divide
Explain in terms of bond polarity why CBr and KOH react together
Br is mor electronegative than C so B is delta negative C is delta positve Lone pair on OH attracted to C+