How may atoms are there in 3.6 g of carbon?
(Relative atomic mass: C = 12.0; Avogadro constant = 6.02 × 10^23 mol-1)
A. 1
B. 0.3
C. 6.02 × 10^23
D. 3 × 6.02 × 10^23
2)
Which of the following substances, when added to sodium hydroxide solution, will lower the pH value of the solution?
(1) NaHSO4(s)
(2) NaCl(s)
(3) HCl(aq)
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
3)
In which of the following cases is there a complete reaction?
A. 25.0 cm3 of 0.10 M sulphuric acid and 25.0 cm3 of 0.20 M sodium carbonate solution.
B. 25.0 cm3 of 0.10 M ethanoic acid and 25.0 cm3 of 0.20 M sodium hydroxide solution.
C. 25.0 cm3 of 0.10 M phosphoric acid and 10.0 cm3 of 0.30 M potassium hydroxide solution.
D. 25.0 cm3 of 0.10 M hydrochloric acid and 25.0 cm3 of 0.20 M ammonia solution.
4)
7.98 g of iron(III) oxide was heated in a stream of excess carbon monoxide.What mass of metallic iron
was left?
A. 5.58 g B. 6.20 g
C. 0.18 g D. 11.34 g
唔該解釋埋點解..
仲有..如果選項冇你計出黎既ans..那你照給我你計出來的答案吧
有勞
更新1:
5) . Which of the following substances have pH value smaller than 7? (1) Milk of magnesia (2) Kettle cleaner (3) Vinegar A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) p.s.第4題不用答
更新2:
ps第1,2,4題不用答 只需要答第3和第5題
更新3:
請explain
