A 3.75 g sample of limestone, CaCO3, contains 1.80 g of oxygen and 0.450 g of carbon. What mass of calcium is present in the sample?

a. 1.00 g
b. 1.25 g
c. 1.50 g
d. 1.75 g
e. 2.00 g

The mass of calcium in this sample is 1.50 grams (option c is correct)

Explanation:

Step 1: data given

Mass of CaCO3 = 1.80 grams

Molar mass CaCO3 = 100.09 g/mol

Mass of oxygen = 1.80 grams

Mass of carbon = 0.450 grams

Step 2: Calculate mass %

Mass % oxygen = (1.80 grams / 3.75 grams ) *100 %

Mass % oxygen = 48.0 %

Mass % carbon = (0.450 grams / 3.75 grams) * 100 %

Mass % carbon = 12.0 %

Step 3: Calculate mass % calcium

Mass % Ca = 100 % - 48.0 % - 12.0 %

Mass % Ca = 40.0 %

Step 4: Calculate mass Calcium

Mass Calcium = 3.75 grams * 0.40

Mass Calcium = 1.50 grams

The mass of calcium in this sample is 1.50 grams (option c is correct)

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.