Question 12 unsaved 3cu(s) + 8hno3(aq) → 3cu(no3)2(s) + 2no(g) + 4h2o(l) how many grams of cu would be needed to react with 2.0 mol hno3? : 1.50 g 47.6 g 95.3 g 63.5

47.6 g

Solution:

The balance chemical equation is as follow,

3 Cu + 8 HNO₃ → 3 Cu(NO₃)₂ + 2 NO + 4 H₂O

According to equation,

8 mol HNO₃ required = 190.63 g of Cu (3 moles)

So,

2 mol HNO₃ will require = X g of Cu

Solving for X,

X = (190.63 g × 2 mol) ÷ 8 mol

X = 47.65 g of Cu

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.

e

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

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.