How many grams of barium hydroxide are required to dissolve in 156 g of water to make a 0.247 m solution? Molar mass of Ba(OH)2: 171.346

Which of the following statements is not true? • a. covalent compounds have low melting and boiling points. • ob. covalent bonds between atoms of a compound are relatively weak compared to bonds between molecules. • c. covalent bonds occur between nonmetals. • d. covalent compounds are often gases or liquids.

Light waves can move through , but they travel fastest when they move through a(n) .

Answer asap : ( a. how does mucus prevent the entry of pathogens? b. describe two ways white blood cells protect us from pathogens.