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In chemistry a number is represented in the form $ N \times 10^n $ . This method of expressing the number is called scientific notation. What is the value of ‘N’ here.
What is the correct scientific notation for 0.00016 ?
How many significant digits are there in 0.25 ?
Significant figures are the digits that carry meaning and contribute to the value of a number. In 0.25, both digits (2 and 5) are significant figures, so the answer is 2 significant digits.
What is the number of neutrons in $ Zn^{2+} $ ion (Atomic mass number = 70) (IITJEE 1979)
Find the total number of electrons in one molecule of carbon dioxide.
A gaseous mixture contains oxygen and nitrogen in the ratio of 1 : 4 by weight. Therefore, the ratio of their number of molecules is
The ratio by weight = 1 / 4 $ \therefore Ratio of moles = { 1/32 \over 4 /28 } = { 28 \over 4 \times 32 } = { 7 \over 32 } $
Identify the incorrect unit conversion factor.
The correct unit conversion factors are: 1 cm^3 = 1 mL, 1 cm = 10 mm, and 60 s = 1 min. Since all the given options are incorrect, the answer is 'None of these'.
$ 90 g KClO_3 $ on heating gives 2.96g KCl and 1.92g oxygen. Which of the following laws is illustrated by this statement ?
The statement illustrates the law of mass conservation, which states that matter can neither be created nor destroyed in a chemical reaction. The total mass of reactants (90 g KClO3) is equal to the total mass of products (2.96 g KCl + 1.92 g O2).
Naturally occuring Boron consists of two isotopes having atomic masses 10.01 and 11.01 respectively. Calculate the percentage of both the isotopes in natural Boron (Atomic mass of natural Boron = 10.81)
Let the % of isotope with atomic mass 10.01 be ‘x’ % of isotope with atomic mass 11.01 = 100-x Avg at mass = $ { 10.01x + (100 - x)11.01 \over 100 } = 10.81(Given) $
Calculate the mass percent of Na and S in sodium sulphate.
To calculate the mass percent of Na and S in sodium sulphate (Na2SO4), we need to find the atomic masses of Na, S, and O and then calculate their percentages. The atomic masses are: Na = 23, S = 32, O = 16. The molar mass of Na2SO4 is (2 x 23) + 32 + (4 x 16) = 142. The mass percent of Na = (2 x 23)/142 x 100% = 32.39% and the mass percent of S = 32/142 x 100% = 22.54%.
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