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.

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 compiles data on the solubility of bromine in water at different temperatures from several websites and textbooks. Source Temperature / °C Solubility of bromine A 5 3.90 g per 100 $\mathrm{cm^3}$ of water B 15 1.15 $\mathrm{cm^3}$ of liquid bromine…

Suggest why the times measured for equal masses of the two metals are not a valid basis for comparing their reactivity.

A sealed flask contains 8.0 g of helium and 120 g of argon. What is the ratio of the number of atoms of argon to the number of atoms of helium in the flask? A. 0.067 B. 0.67 C. 1.5 D. 15

The enthalpy of combustion of $\ce{C19H40}$ is $-12\,660\ \mathrm{kJ\,mol^{-1}}$. (i) Calculate the maximum energy released when 1.50 g of $\ce{C19H40}$ is burned completely. (ii) Determine the maximum temperature increase when $400.0\ \mathrm{cm^3}$ of water…

Propane hydrate, $\ce{C3H8.17H2O}$ ($M_r = 350$), is a crystalline solid that can form in natural gas pipelines at low temperature. What mass of carbon dioxide is produced by the complete combustion of 17.5 g of propane hydrate? A. 2.20 g B. 6.60 g C. 17.5 g…