15.下列物质的用途是利用其化学性质的是( )
| A. | 氧气供给呼吸 | B. | 液氮做制冷剂 | ||
| C. | 稀有气体用于霓虹灯 | D. | 铜线制电缆 |
13.根据元素或原子团的化合价填写表格内的化学式:
0 168758 168766 168772 168776 168782 168784 168788 168794 168796 168802 168808 168812 168814 168818 168824 168826 168832 168836 168838 168842 168844 168848 168850 168852 168853 168854 168856 168857 168858 168860 168862 168866 168868 168872 168874 168878 168884 168886 168892 168896 168898 168902 168908 168914 168916 168922 168926 168928 168934 168938 168944 168952 211419
| -1 Cl | -1 OH | -2 O | -2 CO3 | |
| +1 Na | NaCl | NaOH | Na2O | Na2CO3 |
| +2 Ca | CaCl2 | Ca(OH)2 | CaO | CaCO3 |