Scientist discover that stars in the universe are mostly composed of which elements?

Which is a spectator ion from the following complete ionic equation: H + (aq) + Br - (aq) + K + (aq) + OH - (aq) → H2O (l) + K + (aq) + Br - (aq)

Thallium-207 decays exponentially with a half life of 4.5 minutes. if the initial amount of the isotope was 28 grams, how many grams of the isotope will remain after 7 minutes?

The densities of gases a, b, and c at stp are 1.25 g/l, 2.86 g/l and 0.714 g/l, respectively. calculate the molar mass of each substance. identify each substance as ammonia (nh₃), sulfur dioxide (so₂), chlorine (cl₂), nitrogen (n₂) or methane (ch₄).

What are the two homologous structures?

Where in the body are nitrogen compounds found? a. proteins b. nucleic acids like DNA c. fats d. both a & b

A flask containing 155cm^3 of hydrogen was collected under a pressure of 22.5kPa. What pressure would have been required in order for the volume of the gas to have been 90.0 cm^3 at constant temperature?

Which change is most likely to occur when a molecule of H2 and a molecule of I2 collide with proper orientation and sufficient energy? 1. a chemical change, because a compound is formed 2. a chemical change, because an element is formed 3.

Which substance is a diatomic molecule? a. he b. o2 c. co2 d. h2o?

What is the difference between the electronegativity values of sodium and bromine?

Which of the following elements is the most stable element? argon, manganese, phosphorus, robidium