Which of the following is a clue of a chemical change?

a. balls of wax form when melted wax is poured into ice water

b. iron changes color when heated

c. gas bubbles form in boiling water

d. a gas forms when vinegar and baking soda are mixed?

72.983 rounded to 2 significant figures

50.0 grams of a pure gaseous compound was found to contain 26 grams of oxygen. What is the percentage by weight of oxygen in this compound? Answer in units of g.

Cesium-137, a component of radioactive waste, has a half-life of 30.2 yr. If a sample of waste has an initial activity of 15.0 Ci due to cesium-137, how long will it take for the activity due to cesium-137 to drop to 0.250 Ci?

How many g are equal to 345.7 mg? what conversion factor will you use

Which atom is most likely to attract electrons in a bond? A) K B) Na C) S D) Se

If a gas is moved from a large container to a small container but its temperature and number of moles remain the same, what would happen to the pressure of the gas? It would increase. It would be halved. It would stay the same.

Which of the following would require the largest volume of 0.100 M sodium hydroxide solution for neutralization?: (A) 20.0 mL of 0.0500 M nitric acid (B) 15.0 mL of 0.0500 M hydrobromic acid (C) 5.0 mL of 0.0100 M sulfuric acid (D) 10.0 mL of 0.

Approximately what volume do 3.0 moles of kr gas occupy at stp? 80.0 40.0 l none of the above 20.0

What is the correct formula when Aluminum and Nitrogen are combined? a. Al3N b. AlN c. AlN3 d. Al2N

1-Bromobutane reacts with water to form 1-butanol according to the following equation. C4H9Br (aq) + 2 H2O (l) → C4H9OH (aq) + H3O + (aq) + Br - (aq) The following is a proposed mechanism for the reaction.