H2SO4\mathrm{H}_{2} \mathrm{SO}_{4}H2SO4
HCl\mathrm{HCl}HCl
H−COOH\mathrm{H}-\mathrm{COOH}H−COOH
CH3−COOH\mathrm{CH}_{3}-\mathrm{COOH}CH3−COOH