Some Basic Concepts Of Chemistry Test - 1

The prefix used for 10^-18 is atto-

Additional Information: A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. Each prefix has a unique symbol that is prepended to any unit symbol. Some important prefixes are given below: 

• An atomic mass unit (symbolized AMU or amu) is defined as precisely 1/12 the mass of an atom of carbon-12.
• The carbon-12 (C-12) atom has six protons and six neutrons in its nucleus.
• In imprecise terms, one AMU is the average of the proton rest mass and the neutron rest mass.
• 1 AMU = 1.67377 x 10 ^-27 kilogram or 1.67377 x 10 ^-24 gram.

The standard units of measurement defined by the ISU for the seven base quantities are SI base units All other SI units are derived from it.

Additional Information: 7 Basic SI units with their quantities are: 

The S.I. unit of time is second(s).
Additional Information: A second can be defined as  1/86400th part of a mean solar day,  i.e., =1/86400 × one mean solar day.

• Cisplatin is particularly effective against testicular cancer.
• Taxol (paclitaxel) is a mitotic inhibitor used in cancer chemotherapy.
• AZT is used for helping AIDS victims.

Additional Information: Its mode of action has been linked to its ability to crosslink with the purine bases on the DNA; interfering with DNA repair mechanisms, causing DNA damage, and subsequently inducing apoptosis in cancer cells. 

• A molecule is made up of atoms bonded together. 
• The law of definite proportions, sometimes called Proust's law, or the law of constant composition states that a given chemical compound always contains its component elements in a fixed ratio (by mass) and does not depend on its source and method of preparation.

Since both statements A and B are correct, the correct option is D. 

Here, 6.65 is the coefficient and 10⁴ is the exponent.

Explanation: A coefficient is a number or an alphabet that is multiplied by a variable of a single term or the terms of a polynomial. For example, in the term 7x, 7 is the coefficient. 

• Luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle.
• The SI unit of luminous intensity is the candela, an SI base unit.

• The significant figures of numbers are digits to convey the meaning that contributes to its measurement resolution.
• Non-zero digits are always significant.
• Here, 3256, this number has four non-zero numbers.
• That's why it has four significant figures.

• Electric current is defined as the rate of flow of charge
• Since the charge is measured in coulombs and time in seconds, the electric current unit is Coulomb/Sec ( C/s )
• Where, coulomb/sec is defined as Ampere

So the Ampere is the SI unit of the current.

• The significant figures of numbers are digits to convey the meaning that contributes to its measurement resolution.
• Non-zero digits are always significant.
• Here, the number of Significant figures in 0.001520 is 4.

• Precision indicates how closely repeated measurements match each other.
• Since both the values are close to each other, they are precise and since there is a difference between the mean value and true value, they are not accurate.

• The mole, denoted by the symbol mol, is the SI unit of the amount of substance.
• One mole contains exactly 6.022 140 76 x 10²³ elementary entities.
• This number is the fixed numerical value of the Avogadro constant, N_A, when expressed in the unit mol^–1 and is known as the Avogadro number.
• The value of Avogadro’s number is fixed and the value is N_A = 6.022 x 10²³.

• The significant figures of numbers are digits to convey the meaning that contributes to its measurement resolution.
• Non-zero digits are always significant.
• 6.26 & 0.00267 contains 3 significant figures while 5.8 has two significant figures and 0.03 contains least that is 1.

Therefore, the correct answer is 0.03

• Precision indicates how closely repeated measurements match each other.
• Accuracy indicates how closely a measurement matches the correct or expected value.

Since the readings closely match the result and the expected value, the correct answer is that the values are both accurate and precise. 

The answer is 5 because all non zero digits and zero between the non zero digits are significant.

Move the decimal point to the right of 0.00016 up to 4  places.

The decimal point was moved 7 places to the right to form the number 1.6

Since the numbers are less than 10 and the decimal is moved to the right, so we use a negative exponent here.

⇒ 0.00016 = 1.6 × 10^-4

Explanation: 

• Scientific notation is a form of presenting very large numbers or very small numbers in a simpler form.
• Scientific notation is used to represent the numbers that are very huge or very tiny in a form of multiplication of a single-digit number and 10 raised to the power of the respective exponent.
• The exponent is positive if the number is very large and it is negative if the number is very small. 

Let atomic weight of element X is x and that of element Y is y.

The correct option is B

7.5

In addition, the result cannot have more digits to the right of the decimal point than either of the original numbers.

Since there is only 1 digit after the decimal point in 0.8 so the result 7.48 should be rounded off to 1 decimal point i.e. 7.5.

Molecular mass: The sum of the atomic masses of all the atoms in a molecule of a substance is called the molecular mass of the molecule.

Generally, we use relative atomic masses of atoms for calculating the molecular mass of 1 mole of any molecular or ionic substances.

The molecular formula of glucose is C₆H₁₂O₆

• The atomic mass of H = 1
• The atomic mass of C = 12
• The atomic mass of O = 16

Molecular mass of C₆H₁₂O₆ = 12 (Atomic mass of Hydrogen) + 6(Atomic mass of carbon) + 6(Atomic mass of oxygen)

= 12 × 1 + 6 × 12 + 6 × 16

= 12 + 72 + 96 = 180 u.