【简答题】下列物质N 2 、H 2 O、N a 2 O 2 、CaCl 2 、KOH、NaF中,只含有共价键的物质是_________________,只含有离子键的物质是___________,既含有离子键,又含有共价键的物质是____________。
【单选题】The difference in water spray pattern between the high-velocity tip and low-velocity applicator used with the all-purpose nozzle is due to ______.
A.
a difference in water pressure
B.
the method of breaking up the water stream
C.
the length of the applicator
【单选题】What is the phase velocity of a mixture of waves?
A.
The velocity of the individual waves
B.
The velocity of energy flow
C.
The velocity of the modulation
D.
Half the group velocity
【简答题】PHV(peak height velocity)
【简答题】(2)图中②所指的物质是________ ,③所指的物质是___________。
【单选题】下列各组物质中,物质之间通过一步反应就能实现图示变化的是 物质编号 物质转化关系 a b c d ① FeCl 2 FeCl 3 Fe CuCl 2 ② NO NO 2 N 2 HNO 3 ③ Na 2 O Na 2 O 2 Na NaOH ④ Al 2 O 3 NaAlO 2 Al Al(OH) 3
【单选题】In the velocity parallelogram drawn based on the theorem of composition of velocities,
A.
the absolute velocity is diagonal of the parallelogram formed by the transport velocity and relative velocity.
B.
the transport velocity is diagonal of the parallelogram formed by the absolute velocity and relative velocity.
C.
the relative velocity is diagonal of the parallelogram formed by the transport velocity and absolute velocity.
D.
the algebraic sum of the projections of the absolute velocity, transport velocity and relative velocity on any axis is equal to zero.
【单选题】锯齿波触发电路由锯齿波产生与相位控制、( )、强触发与输出、双窄脉冲