General
✓✗Concentrated nitric acid used in the laboratory is 68% HNO3 by mass, with a density of 1.504 g mL−1. The molarity of the acid is about (H = 1, N = 14, O = 16)
- 16.2 M
- 32.4 M
- 10.8 M
- 6.8 M
General
✓✗Nitrogen forms several oxides: N2O, NO, N2O3, NO2 and N2O5. The masses of oxygen combining with a fixed mass of nitrogen in these oxides are in the ratio
- 2 : 1 : 3 : 1 : 5
- 1 : 1 : 1 : 1 : 1
- 1 : 2 : 2 : 4 : 5
- 1 : 2 : 3 : 4 : 5
General
✓✗The number of electrons in 1.6 g of CH4 is approximately
- 1 × 1023
- 6 × 1023
- 6 × 1022
- 3 × 1023
General
✓✗The molar mass of CuSO4·5H2O is (Cu = 63.5, S = 32, O = 16, H = 1)
- 159.5 g mol−1
- 231.5 g mol−1
- 177.5 g mol−1
- 249.5 g mol−1
General
✓✗The volume of hydrogen at STP liberated when 2.4 g of magnesium reacts with excess dilute HCl is (Mg = 24)
- 1.12 L
- 22.4 L
- 2.24 L
- 4.48 L
General
✓✗The density of a 3 M solution of NaCl is 1.25 g mL−1. The molality of the solution is (NaCl = 58.5)
- 3.00 m
- 2.40 m
- 2.79 m
- 3.24 m
General
✓✗The volume of CO2 at STP evolved when 10 g of CaCO3 reacts with excess HCl is
- 2.24 L
- 1.12 L
- 4.48 L
- 22.4 L
General
✓✗Carbon and oxygen form two oxides containing 42.9% and 27.3% carbon respectively. The masses of oxygen combining with a fixed mass of carbon in the two oxides are in the ratio
- 2 : 1
- 1 : 2
- 3 : 8
- 1 : 1
General
✓✗1.0 g of H2 has the same number of molecules as
- 28 g of N2
- 18 g of H2O
- 16 g of CO
- 14 g of N2
General
✓✗Which of the following is a pure substance?
- Brass
- Air
- Distilled water
- Sea water
General
✓✗The volume occupied by 8.8 g of CO2 at STP is
- 4.48 L
- 8.96 L
- 22.4 L
- 2.24 L
General
✓✗If the atomic mass unit were defined as one-sixth of the mass of a carbon-12 atom instead of one-twelfth, the molecular mass of water on this scale would be
- 18 u
- 3 u
- 36 u
- 9 u
General
✓✗A sample of 2.0 g of impure zinc reacts with excess HCl and gives 0.56 L of H2 at STP. The percentage purity of the zinc is (Zn = 65)
- 65%
- 56%
- 81.25%
- 92.5%
General
✓✗When 22.4 L of H2(g) is mixed with 11.2 L of Cl2(g), each at STP, the number of moles of HCl(g) formed is
- 0.5 mol
- 1.5 mol
- 1 mol
- 2 mol
General
✓✗Which of the following statements about Dalton's atomic theory is correct?
- It explained the laws of conservation of mass, constant proportions and multiple proportions
- It distinguished between atoms and molecules of elements
- It proposed that atoms are made of electrons, protons and neutrons
- It explained the law of gaseous volumes