Chemistry, 30.05.2020 18:57 ajm1132005

If 23.6 grams of a substance reacts with 42.5 grams of another substance, what would we expect the mass of the products to be after the reaction?

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Answer from: bri9263

The correct answer is 66.1 g

Explanation:

According to Law of Conservation of the Mass, the mass of an isolated system is neither created or destroyed during chemical reactions. It is transformed. So, in a chemical reaction, the atoms of reactants are reoganizated by forming other compounds but the mass is conserved. Thus, the total mass of reactants is always equal to the total mass of products. If 23.6 g of a substance reacts with 42.5 g of another substance, the total mass of the products will be equal to the total mass of reactants:

23.6 g + 42.5 g = 66.1 g reactants = 66.1 g products

Answer from: Quest

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

Answer from: Quest

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

explanation

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 $3d$ have energy higher than those in the $4 s$ orbital while lower than those of the $4 p$ orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the $4s$ orbital is therefore filled right after $3p$ orbitals and before $3 d$ orbitals.

potassium has electron configuration $[\text{ar}] 4 s^{1}$ and calcium $[\text{ar}] 4 s^{2}$ . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration $[\text{ar}] 4 s^{2} \; 3d^{1}$ 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 $ns^{2} \; (n-1) p^{1}$ and should be highlighted as well.