What is meant by pure substances?

What volume of a 0.25 m solution can be made using 0.55 moles of ca(oh)2

1. emigration the movement of people from one place to another 2. immigration a situation in which resources are being used up at a faster rate than they can be replenished 3. migration the leaving of one's homeland to settle in a new place 4. overpopulation the movement of people to a new country 5. sustainable development a situation in which the birth rate is not sufficient to replace the existing population 6. underpopulation the ability to meet current needs without reducing the ability to meet future needs 7. unsustainable development the increase in the population of a city 8. urbanization a situation in which the number of people exceeds the available natural resources in an area

Prior to the mt. st. helens eruption on may 18, 1980, satellite and topographic views of the volcano were captured. based on the topographic map of mt. st. helens, what is the contour interval if the volcano height is 2,950 m? question 9 options: 600 m 400 m 750 m 500 m