Counting particles by mass: The mole

(i) State the number of protons, electrons and neutrons in $\ce{^{85}Rb+}$. (ii) State the full electron configuration for $\ce{^{85}Rb+}$. (iii) The relative atomic mass, $A_r$, of Rb is 85.47. Isotope Mass Percent abundance $\ce{^{x}Rb}$ 72.17 %…

How many ions are present in 142 g of $\ce{Na2SO4}$? $M(\ce{Na2SO4}) = 142\ \mathrm{g\,mol^{-1}}$ A. 1 B. 3 C. $6.02 \times 10^{23}$ D. $1.81 \times 10^{24}$

What is the empirical formula of an alcohol with 60.0 % mass carbon and 13.4 % mass hydrogen? A. $\ce{C3H7}$ B. $\ce{C6H16O2}$ C. $\ce{C3H8O}$ D. $\ce{C2H6O}$

Determine the mass of sodium thiosulfate pentahydrate, $\ce{Na2S2O3 * 5H2O}$, needed to prepare 250.0 $\mathrm{cm^3}$ of a 0.2000 $\mathrm{mol\,dm^{-3}}$ solution.

Explain how the 0.2000 $\mathrm{mol\,dm^{-3}}$ solution is prepared in a volumetric flask from the weighed solid.

Suggest how to prepare 100.0 $\mathrm{cm^3}$ of a 0.05000 $\mathrm{mol\,dm^{-3}}$ sodium thiosulfate solution from the 0.2000 $\mathrm{mol\,dm^{-3}}$ solution.

Before use, the EDTA solution was standardized against a standard solution of $\ce{Cu^2+}$ ions. An accurately weighed piece of pure copper wire was dissolved in the minimum volume of concentrated nitric acid and the mixture was warmed gently until no more…

Anhydrous copper(II) chloride, $\ce{CuCl2}$, takes up water vapour from the air, so it cannot be weighed out accurately to make a standard solution. Suggest a laboratory procedure that would remove all of the absorbed water from a sample of solid $\ce{CuCl2}$…

For the AAS method, a series of standards of known concentration was prepared by diluting a stock solution of $\ce{Cu^2+}$ ions. The instrument was zeroed with deionized water and the absorbance of each standard was recorded. (i) Draw the line of best fit for…

What is the number of hydrogen atoms in 0.0500 mol of hydrated magnesium sulfate, $\ce{MgSO4 * 7H2O}$? A. $3.01 \times 10^{22}$ B. $4.21 \times 10^{23}$ C. $2.11 \times 10^{23}$ D. $4.21 \times 10^{22}$