In an experiment, hydrochloric acid reacted with different volumes of sodium thiosulfate in water. A yellow precipitate was formed during the reaction. A cross drawn at the base of each flask became gradually invisible due the formation of this yellow precipitate. The time taken for the cross to become invisible was recorded. A partial record of the experiment is shown. Experimental Record Flask Volume of HCl Volume of Sodium Thiosulfate Volume of Water Time 1 10 mL 10 mL 40 mL 14 seconds 2 10 mL 20 mL 30 mL 3 10 mL 30 mL 20 mL 4 10 mL 40 mL 10 mL Based on your knowledge of factors that affect the rates of chemical reactions, predict the trend in the last column of the experimental record. Use complete sentences to explain the trend you predicted. You do not have to determine exact values for time; just describe the trend you would expect (increase or decrease) and why it occurs. (5 points)

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Explanation:

The time taken for the cross to disappear is a measure of the rate of reaction. Let us remember that the rate of reaction depends on the concentration of the reactants.

The concentration of reactants increases when the volume of water added decreases. This is because, more reactant particles are available in the system and they collide more frequently with each other.

Since the volume of added water decreases as we move down the table, the concentration of the reactants increases hence it takes lesser time for the cross to disappear as we move down the table.

Hence, the last column(time) decreases as we more down the table due to increase in concentration.

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.

a is the correct answer