If a neutral atom of oxygen has 8 protons, 8 electrons, and 7 neutrons, what number is the mass number of this atom?

A. 8

B. 15

C. 16

D. 23

A sample contains 25% parent isotope and 75% daughter isotopes. If the half-life of the parent isotope is 72 years, how old is the sample?

What is the molecular formula of the compound whose molar mass is 90.08 g/mol and empirical formula is CH2O?

An aquifer is an underground formation containing groundwater. a. True b. False

Explain, in terms of collision theory, how increasing temperature affects the rate of a reaction.

Which has a higher specific heat value water or iron?

Change of state may occur when?

During the combustion of 2.00 g of coal, the temperature of 500 g of water inside the calorimeter increased from 25.0°c to 43.7°c. the specific heat of water is 4.18 j/g·°c. how much heat did the reaction generate?

Catalysts are substances that increase the rate of reaction but can be recovered unchanged at the end of the reaction. Catalysts can be classified as either homogeneous (same state as reactants) or heterogeneous (different state than reactants).

How many molecules are there in 79g of Fe2O3?

Which of the following elements is an alkall metal?