Some Basic Concepts of Chemistry — JEE Main PYQs

The concentration of fluoride, lead, nitrate and iron in a water sample from an underground lake was found to be $1000\mathrm{ppb},40\mathrm{ppb},100\mathrm{ppm}$ and 0.2 ppm , respectively. This water is unsuitable for drinking due to high concentration of :

The ratio of masses of oxygen and nitrogen in a particular gaseous mixture is $1:4$. The ratio of number of their molecule is:

The molarity of a solution obtained by mixing 750 mL of $0.5(\mathrm{M})\mathrm{HCl}$ with 250 mL of $2(\mathrm{M})\mathrm{HCl}$ will be:

A gaseous hydrocarbon gives upon combustion 0.72 g of water and 3.08 g of ${\mathrm{CO}}_2$. The empirical formula of the hydrocarbon is:

The density of a solution prepared by dissolving 120 g of urea (mol. Mass $=60\mathrm{u}$) in 1000 g of water is $1.15\mathrm{g}/\mathrm{mL}$. The molarity of this solution is :

A 5.2 molal aqueous solution of methyl alcohol, ${\mathrm{CH}}_3\mathrm{OH}$, is supplied. What is the mole fraction of methyl alcohol in the solution?

In the reaction. $2{\mathrm{Al}}_{(\mathrm{s})}+6{\mathrm{HCl}}_{(\mathrm{s})}⟶2{\mathrm{Al}}_{(\mathrm{aq})}^{3+}+6{\mathrm{Cl}}_{(\mathrm{aq})}^{-}+3{\mathrm{H}}_{2(\mathrm{g})}$,

The density (in $\mathrm{g}{\mathrm{mL}}^{-1}$ ) of a 3.60 M sulphuric acid solution that is $29\%{\mathrm{H}}_2{\mathrm{SO}}_4$ (Molar mass $=98\mathrm{g}{\mathrm{mol}}^{-1}$ ) by mass will be

How many moles of magnesium phosphate, ${\mathrm{Mg}}_3{\left({\mathrm{PO}}_4\right)}_2$ will contain 0.25 mole of oxygen atoms?

Density of a 2.05 M solution of acetic acid in water is $1.02\mathrm{g}/\mathrm{mL}$. The molality of the solution is

Two solutions of a substance (non electrolyte) are mixed in the following manner. 480 ml of 1.5 M first solution +520 mL of 1.2 M second solution. What is the molarity of the final mixture?

If we consider that $\frac{1}{6}$, in place of $\frac{1}{12}$; mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

An organic compound having molecular mass 60 is found to contain $\mathrm{C}=20\%,\mathrm{H}=6.67\%$ and $\mathrm{N}=46.67\%$ while rest is oxygen. On heating it gives ${\mathrm{NH}}_3$ alongwith a solid residue. The solid residue give violet colour with alkaline copper sulp …

$6.02\times 10^{20}$ molecules of urea are present in 100 ml of its solution. The concentration of urea solution is