Q. No.
A significant figure is defined as :
| 1. | The total number of digits in a number, including the last digit that represents the uncertainty of the result. |
| 2. | The total number of digits in a number, excluding the last digit, which represents the uncertainty of the result. |
| 3. | The total number of digits in a number including the last digit that represents the certainty of the result. |
| 4. | The total number of last digits that represents the uncertainty of the result. |
The chloroform contamination level in water is 15 ppm (by mass of chloroform). Calculate the molality of chloroform in this water sample, which represents the number of moles of chloroform dissolved per kilogram of pure water solvent:
| 1. | 3.25 × 10-4
|
2. | 1.5 × 10-3
|
| 3. | 7.5 × 10-3
|
4. | 1.25 × 10-4 |
If the speed of light is 3.0 × 108 m s–1, then the distance covered by light in 2.00 nanoseconds will be:
1. 0.500 m
2. 0.600 m
3. 0.700 m
4. 0.800 m
In a reaction A + B2 → AB2,
A will act as a limiting reagent if :
| i. | 300 atoms of A reacts with 200 molecules of B |
| ii. | 2 moles A reacts with 3 moles B2 |
| iii. | 100 atoms of A reacts with 100 molecules of B |
| iv. | 5 moles A reacts with 2.5 moles B |
| v. | 2.5 moles A reacts with 5 moles B2 |
Choose the correct option:
| 1. | (i), (ii) | 2. | (i), (ii), (v) |
| 3. | (ii), (v) | 4. | All |
If 10 volumes of H₂ react completely with 5 volumes of O₂, what volume of water vapor will be produced under the same conditions of temperature and pressure?
1. 9
2. 8
3. 10
4. 11
15.15 pm in the basic unit will be
1. 1.515 × 10–12 m
2. 2.57 × 10–11 m
3. 2.87 × 10–11 m
4. 1.515 × 10–11 m
Determine the number of significant figures that should be present in the final answers for each of the following expressions:
| I. | 0.02856 × 298.15 × 0.112 / 5785 |
| II. | 5 × 5.364 |
| III. | 0.0125 + 0.7864 + 0.0215 |
| 1. | 4, 4, 3 | 2. | 3, 3, 4 |
| 3. | 4, 3, 4 | 4. | 3, 4, 4 |
The molar mass of naturally occurring Argon isotopes is:
| Isotope | Isotopic molar mass | Abundance |
| 36-Ar | 35.96755 g mol–1 | 0.337% |
| 38-Ar | 37.96272 g mol–1 | 0.063% |
| 40-Ar | 39.9624 g mol–1 | 99.600% |
| 1. | 49.99947 g mol-1 | 2. | 39.99947 g mol-1 |
| 3. | 35.59947 g mol-1 | 4. | 45.59947 g mol-1 |
The mass of CaCO3 required to react completely with 25 mL of 0.75 M HCl according to the given reaction would be:
\(CaCO_3 (s)\ + \ HCl (aq)\ \rightarrow CaCl_2(aq)\ + CO_2(g)\ \\~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+ H_2O(l)\)
1. 0.36 g
2. 0.09 g
3. 0.96 g
4. 0.66 g
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