1. What is the sum of all coefficients when the following equation is balanced using the smallest possible whole numbers?
__ C2H2 + __O2 →__CO2 + __H2O
2. 1.7 g of NaNO3 (Mr = 85) is dissolved in water to prepare 0.20 dm3 of solution. What is the concentration of the resulting solution in mol dm–3?
3. How many molecules are present in a drop of ethanol, C2H5OH, of mass 2.3×10−3 g?
(L = 6.0×1023mol–1)
4. Which sample has the greatest mass?
A. 1 mol of SO2
B. 2 mol of N2O
C. 2 mol of Ar
D. 4 mol of NH3
5. The relative molecular mass of a gas is 56 and its empirical formula is CH2. What is the molecular formula of the gas?
6. Which statement about the numbers of protons, electrons and neutrons in an atom is always correct?
A. The number of neutrons minus the number of electrons is zero.
B. The number of protons plus the number of neutrons equals the number of electrons.
C. The number of protons equals the number of electrons.
D. The number of neutrons equals the number of protons.
7. Which property generally decreases across period 3?
A. Atomic number
C. Atomic radius
D. First ionization energy
8. Which property increases down group 1?
A. First ionization energy
B. Melting point
9. What is the correct Lewis structure for hypochlorous acid, a compound containing chlorine, hydrogen and oxygen?
10. Which compound forms hydrogen bonds in the liquid state?