How many atoms are in 197 g of calcium?

After watching the video "zinc strip in copper nitrate solution", and reading the instructions, click on the link labeled "start" just below the drawing of the pencil tip. follow the direction to complete the 3x3 grid. answer the below questions for the portion of the activity in which sn(s) is placed in agno3(aq)

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

Select the correct answer. why are scientific models important in the study of science? a. they always involve critical mathematical calculations. b. they scientists understand complex ideas and objects that aren’t easy to handle. c. they enable scientists to popularize their work in society. d. they are required when conducting any peer review process. e. they are necessary for turning a hypothesis into a law.