Chapter 1 2018/2019
Chapter 1 2018/2019
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a) Bromine has proton number of 35. FIGURE 1 shows a mass spectrum of bromine.
i. Write the notations for all isotopes of bromine.
[2 Marks]
ii. Calculate the relative atomic mass of bromine.
[2 Marks]
b) A reagent bottle contains a stock solution of 0.90 % by mass of sodium chloride, NaCl. The density of the solution is 1.00 g cm–3. Calculate
i. The mole fraction of NaCl.
[4 Marks]
ii. The molality of NaCl solution.
[2 Marks]
iii. The volume of the stock solution required to prepare 100 mL of 0.01 M NaCl solution.
[3 Marks]
c) Silicon tetrachloride, SiCl4 can be prepared by heating silicon in excess chlorine gas.
Si (s) + 2 Cl2 (g) → SiCl4 (l )
i. Calculate the mass of silicon needed to produce 400 g of SiCl4, if the percentage yield is 42.5 %.
[5 Marks]
ii. If 15 mol of chlorine is used, determine the amount (mole) of unreacted chlorine.
[3 Marks]
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