Unpacking Salts: Formulas, Parents, and Families
Understanding Chemical Identities and Relationships
Salts are fascinating compounds formed when acids and bases react. They're all around us, from the table salt we use daily to minerals in the earth. This activity helps us dig into their chemical identities and relationships.
Aim of the Activity
- Write the chemical formulas for a given list of salts.
- Identify the parent acid and base from which each salt is formed.
- Understand the concept of a "salt family" and identify different families among the given salts.
Materials (No Lab Needed!)
All you need for this activity is your knowledge of chemistry!
Procedure
Let's break down each salt:
- Write the chemical formula for each salt. Remember to balance the valencies of the cation (positive ion from the base) and anion (negative ion from the acid).
- Identify the parent acid (the acid that provides the negative radical/anion) for each salt.
- Identify the parent base (the base that provides the positive radical/cation) for each salt.
- Once we've done this for all salts, we'll look for common positive or negative radicals to group them into families.
Observations & Explanations
Let's analyze each salt:
1. Potassium Sulphate
Formula: $K_2SO_4$
Parent Acid: Sulphuric acid ($H_2SO_4$) (provides $SO_4^{2-}$)
Parent Base: Potassium hydroxide ($KOH$) (provides $K^+$)
2. Sodium Sulphate
Formula: $Na_2SO_4$
Parent Acid: Sulphuric acid ($H_2SO_4$) (provides $SO_4^{2-}$)
Parent Base: Sodium hydroxide ($NaOH$) (provides $Na^+$)
3. Calcium Sulphate
Formula: $CaSO_4$
Parent Acid: Sulphuric acid ($H_2SO_4$) (provides $SO_4^{2-}$)
Parent Base: Calcium hydroxide ($Ca(OH)_2$) (provides $Ca^{2+}$)
4. Magnesium Sulphate
Formula: $MgSO_4$
Parent Acid: Sulphuric acid ($H_2SO_4$) (provides $SO_4^{2-}$)
Parent Base: Magnesium hydroxide ($Mg(OH)_2$) (provides $Mg^{2+}$)
5. Copper Sulphate
Formula: $CuSO_4$
Parent Acid: Sulphuric acid ($H_2SO_4$) (provides $SO_4^{2-}$)
Parent Base: Copper(II) hydroxide ($Cu(OH)_2$) (provides $Cu^{2+}$)
6. Sodium Chloride
Formula: $NaCl$
Parent Acid: Hydrochloric acid ($HCl$) (provides $Cl^-$)
Parent Base: Sodium hydroxide ($NaOH$) (provides $Na^+$)
7. Sodium Nitrate
Formula: $NaNO_3$
Parent Acid: Nitric acid ($HNO_3$) (provides $NO_3^-$)
Parent Base: Sodium hydroxide ($NaOH$) (provides $Na^+$)
8. Sodium Carbonate
Formula: $Na_2CO_3$
Parent Acid: Carbonic acid ($H_2CO_3$) (provides $CO_3^{2-}$)
Parent Base: Sodium hydroxide ($NaOH$) (provides $Na^+$)
9. Ammonium Chloride
Formula: $NH_4Cl$
Parent Acid: Hydrochloric acid ($HCl$) (provides $Cl^-$)
Parent Base: Ammonium hydroxide ($NH_4OH$) (provides $NH_4^+$)
Identifying Salt Families
A salt family consists of salts that share the same positive radical (cation) or the same negative radical (anion).
From the salts listed, we can identify the following families:
-
1. Sulphate Family:
These salts all contain the sulphate ion ($SO_4^{2-}$).
- Potassium sulphate ($K_2SO_4$)
- Sodium sulphate ($Na_2SO_4$)
- Calcium sulphate ($CaSO_4$)
- Magnesium sulphate ($MgSO_4$)
- Copper sulphate ($CuSO_4$)
-
2. Sodium Salt Family:
These salts all contain the sodium ion ($Na^+$).
- Sodium sulphate ($Na_2SO_4$)
- Sodium chloride ($NaCl$)
- Sodium nitrate ($NaNO_3$)
- Sodium carbonate ($Na_2CO_3$)
-
3. Chloride Family:
These salts all contain the chloride ion ($Cl^-$).
- Sodium chloride ($NaCl$)
- Ammonium chloride ($NH_4Cl$)
Conclusion
This activity helps us understand that salts are formed from the reaction of specific acids and bases. By identifying their constituent ions, we can trace them back to their parent compounds. Furthermore, grouping salts into "families" based on common radicals simplifies their study and classification, highlighting shared chemical properties.
Multiple Choice Questions
1. What is the chemical formula for Copper Sulphate?
- a) $CuCl_2$
- b) $Cu(OH)_2$
- c) $CuSO_4$
- d) $CuO$
2. Which acid is the parent acid for Sodium Nitrate?
- a) Sulphuric acid
- b) Hydrochloric acid
- c) Nitric acid
- d) Carbonic acid
3. Which of the following does NOT belong to the Sodium Salt family?
- a) Sodium chloride
- b) Sodium sulphate
- c) Potassium sulphate
- d) Sodium carbonate