Question

Akia is balancing the equation Na + H2O NaOH + H2. He tries to find the coefficients that will balance the equation.

How could he find the correct coefficients?

by counting each individual atom and making sure the number of each kind of atom is the same in the reactants and the products
by counting the total atoms and making sure the number of atoms in the reactants is the same as the number of atoms in the products
by counting the total mass of each compound and making sure the reactants have more mass than the products
by counting the mass of each atom and making sure the reactants are more massive than the products


Substances A and B react in a ratio of A + B → AB. Colin was combining substance A and substance B to form substance AB. He added 10 g of substance A and 45 g of substance B.

How much of substance AB would Colin make?

10 g
35 g
45 g
55 g


Kiley wants to balance the equation H2 + N2 → NH3. Which would be her first step in balancing an equation?

multiplying the subscripts in the atoms of the reactants together
adding the coefficient 3 in front of H2 and the coefficient 2 in front of NH3
changing the subscripts so they match for the total number of atoms
creating a chart that shows the number of atoms in the reactants and products


Which best describes the law of conservation of mass?

The coefficients in front of the chemicals in the reactants should be based on the physical state of the products.
Products in the form of gases are not considered a part of the total mass change from reactants to products.
When reactants contain both a solid and a liquid, the solid counts toward the overall mass and the liquid does not.
The mass of the reactants and products is equal and is not dependent on the physical state of the substances.


Which property of matter is conserved in chemical reactions and shown by balanced equations?

mass
volume
density
shape

Answer 1

1) How could he find the correct coefficients for Na + H2O → NaOH + H2?
- by counting each individual atom and making sure the number of each kind of atom is the same in the reactants and the products

2) A + B → AB. Colin added 10 g A and 45 g B. How much AB will he make?
- 55 g (mass of product = total mass of reactants)

3) Kiley wants to balance H2 + N2 → NH3. Her first step should be:
- creating a chart that shows the number of atoms in the reactants and products

4) Which best describes the law of conservation of mass?
- The mass of the reactants and products is equal and is not dependent on the physical state of the substances.

5) Which property of matter is conserved in chemical reactions and shown by balanced equations?
- mass