The pressure of a 250mL sample of gas is 105kPa. What would be the pressure if the volume were increased to 375ml

Determine the wavelength of the light absorbed when an electron in a hydrogen atom makes a transition from an orbital in the n=3 level to an orbital in the n=7 level.

To find the enthalpy of a reaction in the lab, you measured the of the reactants and the change during the reaction.

Why is any chemical reaction always balanced? give reasons and explain the easiest way to solve the balancing problems in chemical equations with stoichiometric coefficients upto 20 as hit and trial doesn't always work. give full reasoning