Which element represents 10% of the elements in the human body?

a. calcium

b. nitrogen

c. hydrogen

d. oxygen

Are rocks on Earth's surface stable? What might cause rocks to change? Explain your reasoning.

What happened as a result of people being able to trade and purchase food from other people? A. They lacked proper nutrition. B. They lived shorter lives. C. They had more time to pursue crafts and trades. D. There were large food shortages.

In a 71.4 g sample of nahco 3 3 , how many grams of sodium are present?

Which two particles are found in the nucleus of an atom?

What is true of acids? a. They are poor electrolytes. b. They have a pH above 9. c. They have a pH below 7. d. They have a strong affinity for H ions.

What can form as a result of a chemical reaction?

A solution of orange juice that weighs 500 g contains liquid juice and solid pulp. All of the pulp is removed from the juice. The pulp is found to weigh 50 g. How much would the remaining liquid juice weigh? A. 50 g B. 250 g C. 450 g D. 500 g

Assume 3 molecules of Fe react according to the following equation. 3Fe + 4H2O Fe3O4 + 4H2 How many molecules of H2 are produced? How many water molecules are required? What is the mole ratio of Fe to H2O?

10.0 mL of a HF solution was titrated with a 0.120 N solution of KOH; 29.6 mL of KOH were required to completely neutralize the HF. Calculate the normality of the HF solution.

The number of grams present in 1.35 mol of Fe is