How can we increase the rate of collisions between the reactants in this reaction? mg + 2hcl → mgcl2 + h2 a. increase the concentration of h2 in the reaction mixture. b. decrease the temperature of the reactants in the reaction mixture. c. increase the concentration of mg in the reaction mixture. d. decrease the temperature of the entire reaction mixture. e. decrease the concentration of hcl in the reaction mixture.

Decreasing temperature will lower reaction rate which rules out B and D.

Increasing H2, a reaction product, or decreasing HCL, a reactant, will lower reaction rate too. So A and E is out.

The right answer is C.  Increase the concentration of Mg in the reaction mixture.

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.

> b takes place in the gas phase in an isothermal tubular reactor. the feed is one mole of a per one mole of c, an inert. the entering temperature and pressure are 427°c and 10 atm, respectively. the gas constant r = 0.08206 atm · l/mol · k.