A student carried out a titration to find the exact volume of hydrochloric acid that would neutralise 25.0 cm3 of sodium hydroxide solution. NaOH + HCl → NaCl + H2O
In a different experiment 25.0 cm3 of 0.50 mol dm-3 sodium hydroxide solution reacted with 21.65 cm3 of hydrochloric acid.
Calculate the concentration of the hydrochloric acid.
Give your answer to 2 s. f.

Which of these would be caused by a chemical change? a) the formation of lava. b) sedimantary rock layering over time. c) metamorphic rock forming from igneous. d) metamorphic rock eroding to form sedimentary rock.

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Two people each hold the end of a rope and create waves by moving their arms up and down. this wave is best classified as a transverse wave because a) both the rope particles and the wave are moving in the same direction. b) the wave is moving up and down as the particles of the rope move horizontally. c) the wave is moving horizontally as the particles of the rope move up and down. eliminate d) the wave is moving in a parallel direction with the motion of the person's arms.