Chemists use the mole as the unit for the amount of substance. One mole is equal to 6.02 x 10^23 (just like one dozen is equal to 12). A 40.1 g sample of calcium contains approximately 1 mole of calcium atoms. How many calcium atoms are in a 4 kg sample of calcium?

Explanation:

Hello!

In this case, since we are given 4 kg of a calcium-containing sample, in order to compute the atoms there first need to compute the mass in grams:

Next, via the molar mass and the Avogadro's number, we can compute the atoms as follows:

Best regards!

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.