Which is the most important question for deciding if a chemical reaction has occurred

The chart shows the bid provided by four contractors to complete a job. which contractor is the most cost-effective?

Write a balanced equation showing the formation of copper (ii) nitrite from its elements

Asample of water is taken and kept in a beaker in a freezer at a constant temperature of 0°c. if the system is at dynamic equilibrium, which of these statements is true? the rate of freezing is equal to the rate of melting. the rate of freezing is greater than the rate of melting. the amount of ice is greater than the amount of water. the amount of ice is equal to the amount of water.