Ptolemy believed that earth was at the center of the universe. kepler believed that the sun was at the focus of earth's elliptical orbit. which of these statements best explains why ptolemy and kepler made different observations about the solar system? (2 points) question 28 options: 1) the focus of their study was different. 2) they studied outdated theories and evidences. 3) they could not match the data with the observations. 4) they believed in proposing different theories to strengthen science.

(1.6 × 10-19)(5.0 × 106) = c × 10d identify the missing numbers below to show the result of multiplying the numbers.

Cryolite, na3alf6(s), an ore used in the production of aluminum, can be synthesized using aluminum oxide. start this question by first balance the chemical equation.1.) balance the equation: - alo3(s)+naoh(l)+hf(> na3alf6+h2o(g). 2.) if 17.5 kilograms of al2o3(s), 51.4 kilograms of naoh(l), and 51.4 kilograms of hf(g) react completely, how many kilograms of cryolite will be produced? 3.)which reactants will be in excess, (al2o3, naoh, or hf) 4.)what is the total mass of the excess reactants left over after the reaction is complete in kg?

Astudent conducts an experiment to determine how the amount of water given to a plant affects its growth. what is the independent variable for this experiment?