B. 3.592 g sample of hydrated magnesium bromide, MgBr xH,O, is dried in an oven.

Question

B. 3.592 g sample of hydrated magnesium bromide, MgBr xH,O, is dried in an oven. When the anhydrous salt is removed from the oven, its mass is 2.263 g. What is the value of x? 8. A. How did Mendeleyev know to leave spaces in his periodic table for gallium and germanium? B. With examples, distinguish between Allotropes and Isotopes. 9. Eugenol is the major component in oil of cloves. It has a molar mass of 164.2 g/mol and is 73.14%- and 7.37% H; the remainder is oxygen, what are the emprical and molecular formulas of eugenol? 10. A sealed glass of container with a capacity of exactly 100mL contains 96.0 mL of liquid water at If the water freezes, will the container rupture? Explain with calculations.

Explanation / Answer

B. Mass of hydrated salt is 3.592 grams

Mass of dehydrated salt is 2.263 grams

So, mass of water in the sample = (3.592-2.263) grams = 1.329 grams = (1.329/18) mole = 0.074 mole of H2O

(molar mass of water is 18 g/mole)

No of moles of dehydrated MgBr2 = mass / molar mass = 2.263/ 184 moles= 0.0123 moles

In anhydrous salt: 0.0123 moles of the salt is attached to 0.074 moles of water

So, 1 mole of the salt is attached to 0.074/0.0123 moles = 6 moles of water

So, the formula of the hydrtaed salt is mgBr2.6H20. Hence, x = 6

8.

A) Mendelev placed the elements in his periodic table according to their atomic mass. In doing so, he found that elements with similar chemical properties are staying in the same place according to a column in the table which are known as groups. And he found some empty places in his table where he ciuld not place any element as they were not still known. But he figured out that the chemical properties of those elements are similar to the other elements in the group and he also could determine their molecular weights. In this way he knew to leave places for two unknown elements at that time: gallium and germenium.

B) allotrpes are the different forms of the same element. They have the different molar mass. They also have different physical properties. As for example: graphite and diamond are two allotropes of carbon

But, isotopes are the nuclei of the same element which have same atomic number but different mass number. That means isotopes have same number of proton but different number of neutrons in the nuclus.

As for example: 13C6 and 14C6 are two isotopes if the element carbon

9. The compound has 73.14% C, 7.37% H and (100-73.14-7.37) % = 19.49% O

So the ratio of C, H and O in the compound is

(73.14/12) : (7.37/1): (19.49/16) = 6.095: 7.37: 1.21 = 5 :6:1 ( by making it a simple whole number ratio by dividing by 1.21)

So, the molecule contains C:H:O in 5:6:1 as the simplest whole number ratio

So, empirical formula is C5 H6O

Let us assume that its molecular formula is: (C5H6O)x . Based up on the assumption the molar mass of the compound is : (60+6+16)*x = 82x

So, 82x = 164 .2, x = 2 (approximately)

So, the molecular formula of the compound is C10H12O2

Related Questions

Navigate

• Browse (All)
• Browse B
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.