Video: Applying Knowledge of Salt Solubility

For statements I and II, state for each if they are true or false. I) NaNO₃ will not dissolve in water. II) All nitrates are insoluble in water. If both are true, state if II is a correct explanation for I.


Video Transcript

For statements one and two, state for each if they are true or false. One) NaNO₃ will not dissolve in water. Two) All nitrates are insoluble in water. If both are true, state if two is a correct explanation for one.

NaNO₃ is the symbol for sodium nitrate. We can separate sodium nitrate into its ions to consider whether it would be or wouldn’t be soluble in water. Both Na⁺ and NO₃⁻ are singly charged. Singly charged ions are more likely to be soluble. Broadly speaking, the lower the charge of the ions, the weaker the ionic bonds between them. And the easier it is for water to break it up.

Next, if we look just at the sodium, we can recall that sodium salts are generally soluble, including sodium chloride, sodium sulfate, and sodium carbonate. If we just examine the nitrate ion, the rule of thumb is that nitrates are always soluble. That is assuming we’re dealing with inorganic nitrates. Some nitrates involving complex organic groups aren’t necessarily soluble. Examples include alkali metal nitrates, like lithium nitrate and potassium nitrate. And the nitrates of less commonly soluble metal salts like silver plus and lead two plus. All this suggests that the statement sodium nitrate will not dissolve in water is highly unlikely. And it should come as no surprise that the solubility of sodium nitrate is in fact extremely high. You can dissolve 91.3 grams for every 100 milliliters of water. So you can dissolve almost as much mass of sodium nitrate as you have mass of water. So statement one is most certainly false.

Statement two is that all nitrates, regardless of counterion, are insoluble in water. Even if we hadn’t discussed the general solubility rules for nitrates, the fact that statement one is false means that statement two is also false. Sodium nitrate is definitely soluble in water. So statement two is false. Since both statements are false, we don’t have to address the last part of the question. Two cannot be a correct explanation for one, because both are false.

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