A student investigated the effect of gibberellin（GA）and abscisic acid（ABA）on the germination of wheat grains． The student found out the following information． －The molecular mass of GA is 346 g ． －The molecular mass of ABA is 264 g ． －The range of concentrations at which GA is active in plant tissues is from $$\(1 \times 10^{-6}\)$$ to $$\(1 \times 10^{-5} \mathrm{moldm}^{-3}\)$$ ． －The range of concentrations at which ABA is active in plant tissues is from $$\(1 \times 10^{-6}\)$$ to $$\(1 \times 10^{-4} \mathrm{moldm}^{-3}\)$$ ． －Newly formed wheat grains contain a high concentration of ABA which decreases over time． －When the concentration of ABA falls low enough the GA is able to promote germination． －Wheat germinates best at temperatures from $$\(10^{\circ} \mathrm{C}\)$$ to $$\(25^{\circ} \mathrm{C}\)$$ and without light． Fig． 1.1 shows the germination and early growth of wheat． To test the effects on germination of adding $$\(A B A\)$$ ，the student started by soaking wheat grains for 24 hours in a solution of $$\(1 \times 10^{-6} \mathrm{~mol}^{-3} \mathrm{GA}\)$$ ．These were then split into several groups of 50 grains and a different concentration of ABA was added to each group． The student made a stock solution of ABA with a concentration of $$\(1 \times 10^{-3} \mathrm{~mol} \mathrm{dm}^{-3}\)$$ which was then diluted to make the solutions needed for the investigation． （a）（i）Using the information about ABA above，describe how the student made a stock solution of $$\(1 \times 10^{-3} \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{ABA}\)$$ ． . . . (ii) The student used the stock solution of $$\(1 \times 10^{-3} \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{ABA}\)$$ to prepare a range of dilutions from $$\(1 \times 10^{-4} \mathrm{~mol} \mathrm{dm}^{-3}\)$$ to $$\(1 \times 10^{-7} \mathrm{~mol} \mathrm{dm}^{-3}\)$$ to use in their investigation. Each dilution had a volume of $$\(100 \mathrm{~cm}^{3}\)$$. Describe how the student prepared these dilutions. . . .

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