I don't know what the options were but a material that is very likely going to be challenging to recognize under a microscope as a mixture is a homogeneous mixture. A homogenous mixture is uniform and thus hard to recognize as a mixture. An example is water!
Copper foam and ceramic would answer you question down below<span />
Answer:
5
Explanation:
just subtract 20-25 and 5 is left over which is how much the water when up with the rock.
Answer : The amount of oxygen gas collected are, 0.217 mol
Explanation :
Using ideal gas equation :

where,
P = pressure of gas =
(1 atm = 760 torr)
V = volume of gas = 5 L
T = temperature of gas = 
n = number of moles of gas = ?
R = gas constant = 0.0821 L.atm/mol.K
Now put all the given values in the ideal gas equation, we get:


Thus, the amount of oxygen gas collected are, 0.217 mol
Maalox is the trade name for an antacid and antigas medication used for relief of heartburn, bloating, and acid indigestion in which
4 ml contains
= 320mg of aluminum hydroxide
= 320mg of magnesium hydroxide
= 32mg of simethicone
recommended doses = 4 times * 2 tea spoon = 8 tea spoon/ day
given = 1 tea spoon = 5 ml
8 tea spoon = 40 ml
hence,
amount of aluminum hydroxide = 320/4 * 40 = 3200mg = 3.2 g
amount of magnesium hydroxide = 320/4 * 40 = 3.2 g
amount of simethicone = 32/4 * 40 = 320 mg = 0.32g
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