Molar mass and mole calculations

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.

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…

Each student used a different mass of the hydrated salt. The results of the whole class are shown below ($M_r$ of $\ce{H2O}$ = 18.02). Student Mass of $\ce{CuSO4 * XH2O}$ / g Mass of $\ce{CuSO4}$ / g Loss in mass / g Amount of $\ce{CuSO4}$ / mol Amount of…

Calculate the percentage by mass of hydrogen in compound Y, giving your answer to four significant figures. Use section 7 of the data booklet.

A second sample of Z was converted completely into vapour at a known temperature and pressure. (i) 0.148 g of the vapour occupied 63.7 $\mathrm{cm^3}$ at 110 °C and a pressure of $1.00 \times 10^{5}$ Pa. Calculate the amount, in mol, of Z in this sample. Use…

Calculate the mass of solid potassium hydroxide that has to be weighed out.

4.06 g of hydrated magnesium chloride, $\ce{MgCl2*6H2O}$ ($M_\mathrm{r}$ = 203), is dissolved in water to make 0.250 $\mathrm{dm^3}$ of solution. What is the concentration of chloride ions, in $\mathrm{mol\,dm^{-3}}$, in this solution? A. 0.0400 B. 0.0800 C.…

A student writing a report on chlorine as a disinfectant collects, from several websites and reference books, values for how much chlorine dissolves in pure water at various temperatures. Source Temperature / °C Solubility of chlorine A 5 1.18 g per 100…

A cylinder contains 80 g of argon and 12.0 g of helium. What is the ratio of the number of argon atoms to the number of helium atoms in the cylinder? A. 0.15 B. 0.67 C. 1.5 D. 6.7

The enthalpy of combustion of $\ce{C15H32}$ is $-10\,040\ \mathrm{kJ\,mol^{-1}}$. (i) Calculate the maximum amount of energy that the complete combustion of 1.75 g of pentadecane can release. (ii) The energy from burning the 1.75 g sample is used to heat…