Answer:
D. Radar uses radio, and the siren uses sound waves.
Explanation:
The main difference between the siren passing by and the radar is that radar uses radio waves and siren uses sound waves.
- Sound waves are mechanical waves which requires a material medium for their propagation.
- In a vacuum, the sound waves cannot pass through freely.
- Radar is an electromagnetic wave.
- It is particular of radio waves origin.
- Such waves do not require a material medium for their propagation and hence can be transmitted through a vacuum.
Molarity is the amount of solute molecule (in moles) per 1L of solvent. In this case, the solute is 0.7mol Na2S and the solvent volume is 1.05L. Since the unit in this problem is already mol and L then you don't need to do any conversion of the units. The calculation would be:
molarity = mol of solute / (1L/ volume of solvent)
molarity = 0.7 mol/ (1L/ 1.05L)= 0.67M
I think it’s D.
sorry if it’s wrong
Answer: c. +4
Explanation:
For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.




Here manganese is having an oxidation state of +4 called as cation and oxygen forms an anion with oxidation state of -2. Thus they combine and their oxidation states are exchanged to give
which written in simplest whole number ratios to give neutral 