What is the minimum volume of water required to dissolve 1 gram of calcium?

Quick Answer

The minimum volume of water required to dissolve 1 gram of calcium is approximately 40 milliliters. This is based on the solubility of calcium in water at room temperature, which is around 2400 milligrams per liter. To dissolve 1 gram (1000 milligrams) of calcium, you would need at least 1000/2400 = 0.42 liters = 420 milliliters of water. Rounding up gives approximately 40 milliliters as the minimum volume of water required.

What is Calcium?

Calcium is a chemical element with symbol Ca and atomic number 20. It is a soft gray alkaline earth metal that is essential for living organisms. Calcium is the fifth most abundant element in the earth’s crust and is very reactive. When pure, calcium is a silvery-white metal, but it readily reacts with air and water. Calcium makes up about 3.2% of the earth’s crust by mass.

Some key facts about calcium:

  • Atomic number: 20
  • Atomic weight: 40.078 g/mol
  • Density: 1.55 g/cm3
  • Melting point: 842°C
  • Boiling point: 1484°C
  • Electron configuration: [Ar] 4s2

Calcium is essential for all living organisms, particularly in cell physiology. In humans and animals, calcium is crucial for bone and tooth formation and strength. It is also important for muscle contractions, nerve transmission, and blood clotting. In plants, calcium regulates transport of other nutrients and is involved in enzyme activation. Calcium deficiency can lead to hypocalcemia, which causes muscle spasms and tingling sensations in humans.

Sources of Calcium

Some common natural sources of calcium include:

  • Dairy products like milk, yogurt and cheese
  • Dark leafy greens like spinach, kale and broccoli
  • Fish with edible bones like sardines and salmon
  • Beans, lentils and nuts like almonds
  • Herbs and spices like thyme, dill and oregano
  • Mineral water
  • Calcium-fortified foods like orange juice and cereals

Milk and other dairy products contain the highest amount of calcium. For example, one 8 ounce glass of milk provides 300mg of calcium, meeting about 30% of the daily recommended intake.

Solubility of Calcium in Water

Solubility refers to the maximum amount of a solute that can dissolve in a solvent at a given temperature and pressure. The solubility of calcium in water is important to determine how much can dissolve in a certain volume of water.

Some key points on calcium solubility:

  • Calcium hydroxide Ca(OH)2 is more soluble than calcium carbonate CaCO3 in water
  • Solubility increases with lower pH and higher temperature
  • At 20°C, the solubility of Ca(OH)2 is 1.85 g/L and of CaCO3 is 0.013 g/L
  • Calcium solubility in water at room temperature (25°C) is around 2400 mg/L or 2.4 g/L

So at standard conditions, the maximum solubility of calcium in water is approximately 2400 milligrams per liter. This solubility determines how much calcium can dissolve in a given volume of water at room temperature.

Factors Affecting Calcium Solubility

There are several factors that affect the solubility of calcium compounds:

  • pH – Calcium solubility increases as pH decreases, meaning it is more soluble in acidic solutions than basic solutions. At lower pH, calcium salts dissolve to release more free Ca2+ ions.
  • Temperature – Solubility increases with higher temperatures. More thermal energy allows more calcium to dissociate from compounds and dissolve.
  • Presence of other ions – Ions like phosphate, carbonate, sulfate and fluoride can bind with calcium to form insoluble salts, reducing overall solubility.
  • Crystal structure – Solubility depends on the compound’s crystal lattice structure. For example, calcite CaCO3 has lower solubility than aragonite CaCO3.

So in water, calcium solubility is maximal at lower pH and higher temperatures, in the absence of ions that precipitate it.

Calculating the Minimum Volume of Water for 1 Gram of Calcium

Based on the solubility, we can calculate the minimum volume of water required to completely dissolve 1 gram of calcium at room temperature.

The steps are:

  1. Mass of calcium given: 1 gram = 1000 mg
  2. Solubility of calcium in water at 25°C is 2400 mg/L
  3. To calculate volume:
    • Amount to dissolve (mg) / Solubility (mg/L) = Minimum volume (L)
    • 1000 mg / 2400 mg/L = 0.42 L
  4. 0.42 L x 1000 mL/1 L = 420 mL
  5. Rounding up gives approximately 40 mL as the minimum volume of water required to completely dissolve 1 gram of calcium at room temperature.

So based on the solubility and mass given, the minimum volume is around 40 mL. This provides sufficient water to allow the gram of calcium to completely dissociate into ions.

Does the Source of Calcium Affect Solubility?

Yes, the source of calcium does affect its solubility in water. This is because different calcium compounds have different solubilities based on factors like:

  • Ionic character – Ionic compounds like calcium chloride (CaCl2) are more soluble than covalent compounds like calcium carbonate (CaCO3).
  • Lattice energy – Compounds with weaker lattice energies are more soluble as they more easily break apart into ions.
  • Hydration energy – Hydration energy is released when water solvates the ions. Higher hydration energy means higher solubility.
  • pH – Acidic or alkaline compounds exhibit different solubilities. For example, calcium hydroxide [Ca(OH)2] is more soluble in water than calcium sulfate (CaSO4).
  • Common ion effect – When an ion from the compound is already present in solution, it reduces solubility of the compound via the common ion effect.

Some common calcium compounds ordered from most soluble to least soluble in water at room temperature are:

  1. Calcium nitrate (Ca(NO3)2)
  2. Calcium chloride (CaCl2)
  3. Calcium bromide (CaBr2)
  4. Calcium acetate (Ca(C2H3O2)2)
  5. Calcium hydroxide (Ca(OH)2)
  6. Calcium sulfate (CaSO4)
  7. Calcium oxalate (CaC2O4)
  8. Calcium phosphate (Ca3(PO4)2)
  9. Calcium carbonate (CaCO3)

So yes, the specific calcium compound dramatically impacts its solubility, even though the Ca2+ ion is common. This must be considered when dissolving different forms of calcium in water.

Impact of Temperature on Calcium Solubility

Temperature significantly affects the solubility of calcium in water. Solubility increases with higher temperature due to:

  • Higher kinetic energy of molecules and ions
  • Weakening of intermolecular forces in the calcium compound
  • Increased dissociation into ions
  • Exothermic hydration of Ca2+ and other ions is facilitated

The effect of temperature on calcium solubility can be quantified by the van’t Hoff equation:

ln(S2/S1) = ΔHsol/R [(1/T2) – (1/T1)]


  • S1 and S2 are solubilities at temperatures T1 and T2
  • ΔHsol is the enthalpy of solution
  • R is the gas constant

This equation indicates that solubility increases exponentially with temperature. For example, the solubility of calcium sulfate (CaSO4) at different temperatures is:

Temperature (°C) Solubility of CaSO4 (g/100 g water)
0 0.205
20 0.241
40 0.311
60 0.407
80 0.531
100 0.672

This demonstrates that calcium solubility nearly triples when going from 0°C to 100°C. So higher temperatures allow significantly more calcium to dissolve by disrupting intermolecular bonds and providing energy to form hydrated Ca2+ ions.

Common Applications Where Calcium Solubility is Relevant

Understanding calcium solubility is essential for various chemical applications including:

  • Water treatment – Water hardness caused by dissolved Ca2+ and Mg2+ depends on solubility. Water softeners use ion exchange to remove calcium.
  • Detergents – Calcium and magnesium bind to fatty acids from soap to form insoluble precipitates. Detergents use chelating agents like EDTA to improve cleaning ability in hard water.
  • Food and health – Calcium supplements and fortified foods rely on sufficient solubility for absorption during digestion. Solubility affects bioavailability.
  • Marine environments – Solubility affects calcium concentrations in aquariums and ocean habitats. It impacts skeletal formation in marine organisms.
  • Geological formations – Calcium minerals like limestone and marble are shaped by solubility processes over geological timescales.
  • Cement and construction – The setting and curing of cement involves solid Ca compounds like calcium silicate hydrate dissolving then precipitating from supersaturated pore fluid.

In these applications, factors like pH, mineral form, and temperature must be controlled to optimize calcium solubility as needed. Consideration of solubility principles is key to many chemical processes involving calcium.


In summary, the minimum volume of water required to dissolve 1 gram of calcium is approximately 40 milliliters, based on the solubility of calcium at room temperature being 2400 milligrams per liter. Calcium solubility depends on pH, temperature, and the particular compound being dissolved. Higher temperatures drastically increase calcium solubility. Understanding solubility is critical for applications like water treatment, cement setting, supplements and more. Optimizing solubility requires controlling factors like pH and temperature. Consideration of solubility principles allows effective use of calcium in various chemical processes and applications.

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