Question

Question 6 (1 point)
Stuart measures 10 grams of water into a pan and freezes it. A day later he takes it out of the freezer and observes that it is larger than before. What is the mass of the ice?

a
10 grams
b
11 grams
c
20 grams
d
25 grams
Question 7 (1 point)
Is this equation balanced?

2Zn(OH)2 + 2NaOH → Na2ZnO2 + 2H2O

a
The equation is not balanced but the total number of atoms of each element in the reactants is equal to the total number of atoms of each element in the products.
b
The reaction is balanced because the total number of atoms of each element in the reactants is equal to the total number of atoms of each element in the products, supporting the law of conservation of mass.
c
The equation is balanced because all chemical equations are balanced.
d
The equation is not balanced because the total number of atoms of each element in the reactants is not equal to the total number of atoms of each element in the products.
Question 8 (1 point)
In the chemical compound

Ca3(PO4)2

How many atoms of oxygen are present?

a
2
b
4
c
6
d
8
Question 9 (1 point)
A chemical equation is shown.

2As + 6NaOH → 2Na3AsO3 + 2H2

Does this equation follow the law of conservation of matter?

a
yes, because the reactants contain the same number of arsenic (As) atoms as the products
b
yes, because the mass of the reactants is equal to the mass of the products
c
no, because the reactants contain more oxygen (O) atoms than the products
d
no, because the reactants contain more hydrogen (H) atoms than the products

Answer 1

Q6: a — 10 grams. (Mass doesn't change on freezing.)

Q7: d — The equation is not balanced; the total number of atoms of each element in the reactants is not equal to the total number in the products.

Q8: d — 8 oxygen atoms (PO4 × 2 → 4×2 = 8).

Q9: d — No; the reactants have 6 H atoms but the products have only 4 H atoms (hydrogen is not conserved).