Do you mean; " A blank is a substance that is made by combining two elements?" (I'm not sure if substances is the right term)
If so then the blank is a compound.
Answer:
. All redox reactions occur with a simultaneous change in the oxidation numbers of some atoms. At least two elements must change their oxidation numbers. When an oxidation number of an atom is increased in the course of a redox reaction, that atom is being oxidized
Explanation:
Answer: Physical change
Explanation: Condensation is the phase change of a gas to the liquid state. There is no formation of new products so it does not undergoes chemical change. Any phase change is considered a physical change.
Answer:
12.044 ×10²³ molecules of HCl
Explanation:
Given data:
Number of moles of MgO = 1 mol
Number of molecules of HCl react = ?
Solution:
Chemical equation:
MgO + 2HCl → MgCl₂ + H₂O
with 1 mole of MgO 2 moles of HCl are react.
Number of molecules of HCl react:
1 mole contain 6.022×10²³ molecules
2 mol × 6.022×10²³ molecules / 1 mol
12.044 ×10²³ molecules