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It takes 1 minute for a certain amount of potassium phosphate (KH2PO4) to dissolve in 100 grams of water at 50 °C.

Which of the following will most likely happen if the same sample of potassium phosphate is dissolved in 100 grams of water at 20 °C?

The sample will dissolve in exactly 1 minute.
The sample will dissolve in more than 1 minute.
The collision between particles of the sample will increase.
The collision between particles of the sample will remain constant.

Which family in the periodic table has metals that are usually harder than other metals?

Alkali metals
Alkaline earth metals
Lanthanide series
Transition metals

Generally Solubility and rate of solubility of substances increase with the increase in temperature. So lower the temperature less fast will it dissolve in the same amount of water.

Since at 50 C it takes 1 minute to dissolve, at 20 C which is lower temperature it will take more time to dissolve.

Answer 2

Transition metals

Explanation:-

Hardness depends on the extent of metallic bonding for metals. More the number of electrons more the metallic bonding.

Alkali metals with just 1 valence electron have weak metallic bonding. Alkaline earth metals have just 2 valence electrons. Transition elements has more electrons in penultimate shell and valence shell than lanthanides. Transition metals with most metallic bonding are the hardest