Some Basic Concepts Flashcards
A mixture contains particles of two or more pure substances which may be present in it in any ratio. Hence, their composition is……….
variable
In a homogeneous mixture, the components completely mix with each other. This means particles of components of the mixture are uniformly distributed throughout the bulk of the mixture and its composition is uniform throughout
True
In………………the composition is not uniform throughout and sometimes different components are visible.
heterogeneous mixture
Earlier, two different systems of measurement, i.e., the…………System and the …………… System were being used in different parts of the world.
English
Metric
Assertion: The metric system, which originated in France in late eighteenth century, was more convenient.
Reason: It was based on the decimal system.
Both are correct and correct explanation
National Metrology Institute (NMI), which maintains standards of measurements. This responsibility has been given to the National Physical Laboratory (NPL),
New Delhi
True
The International System of Units (in French Le Systeme International d’Unités — abbreviated as SI) was established by the ……….. General Conference on Weights and Measures (CGPM from ConferenceGenerale des Poids et Measures).
11th
Assertion: Mass standard is defined as the mass of platinum-iridium (Pt-Ir) cylinder that is stored in an airtight jar at International Bureau of Weights and Measures in Sevres, France
Reason: Pt-Ir was chosen for this standard because it is highly resistant to chemical attack and its mass will not change for an extremely long time.
Both are correct
X-rays to determine the atomic density of a crystal of ultrapure silicon, has an accuracy of about 1 part in 10^6 but has not yet been adopted to serve as a standard
True
In 1960 the length of the metre was defined as 1.65076373 × 10^6 times the wavelength of light emitted by a………..laser.
krypton
