Matter can totally be created or destroyed. True False

Sulphur burnt in oxygen forms sulphur dioxide. Calculate the heat given out when 1.6g of sulphur is burnt.

adell [148]

Answer:

Dont know

Explanation:

4 0

3 years ago

What element in the fourth period is an exception to the Aufbau principle? a. Li c. Ca b. Cr d. Br

gulaghasi [49]

The fourth period contains 18 elements, beginning with potassium and ending with krypton. As a rule, period 4 elements fill their 4s shells first, then their 3d and 4p shells, in that order; however, there are exceptions, such as chromium.

Cr. I think

4 0

4 years ago

Caffeine, a stimulant found in coffee, tea, and certain soft drinks, contains C, H, O, and N. Combustion of 1.000 mg of caffeine

Yuliya22 [10]

Answer:

194 g/mol

Explanation:

1) Content of C:

All the C atoms in the 1.000 mg of caffeine will be found in the 1.813 mg of CO₂.

Mass of C in 1.813 mg of CO₂

Since the atomic mass of C is 12.01 g/mol and the molar of of CO₂ is 44.01, there are 12 mg of C in 44 mg of CO₂ and you can set the proporton:

12.01 mg C / 44.01 mg CO₂ = x / 1.813 g CO₂

⇒ x = 1.813 × 12.01 / 44.01 g of C = 0.49475 mg of C

Number of moles of C

number of moles = mass in g / atomic mass = 0.49475×10⁻³ g / 12.01 g/mol = 4.1195×10⁻⁵ moles = 0.041195 milimol

2) Content of H

All the H atoms in the 1.000 mg of caffeine will be found in the 0.4639 mg of H₂O

Mass of H in 0.4639 mg of H₂O

Since the atomic mass of H is 1.008 g/mol and the molar of of H₂O is 18.015 g/mol, there are 2×1.008 mg of H in 18.015 mg of H₂O and you can set the proporton:

2×1.008 mg H / 18.015 mg H₂O = x / 0.4639 mg H₂O

⇒ x = 0.4639 mg H₂O × 2 × 1.008 mg H / 18.015 mg H₂O = 0.051913 mg H

Number of moles of H

number of moles = mass in g / atomic mass = 0.051913 ×10⁻³ g / 1.008 g/mol = 5.1501× 10⁻⁵ moles = 0.051501 milimol

3) Content of N

All the N atoms in the 1.000 mg of caffeine will be found in the 0.2885 mg of N₂

Mass of N in 0.2885 mg of N₂ is 0.2885 mg

Number of moles of N

number of moles = mass in g / atomic mass = 0.2885 ×10⁻³ g / 14.007 g/mol = 2.0597× 10⁻⁵ moles = 0.020597 milimol

4) Content of O

The mass of O is calculated by difference:

Mass of O = mass of sample - mass of C - mass of H - mass of N

Mass of O = 1.000 mg - 0.49475 mg C - 0.051913 mg H - 0.2885 mg N

Mass of O = 0.1648 mg

Moles of O = 0.1648 × 10 ⁻³ g / 15.999 g/mol = 1.0303×10⁻⁵ mol = 0.01030 milimol

5) Ratios

Divide every number of mililmoles by the smallest number of milimoles:

C: 0.041195 / 0.01030 = 4
H: 0.051501 / 0.01030 = 5
N: 0.020597 / 0.01030 = 2

O: 0.01030 / 0.01030 = 1

C: 4
H: 5
N: 2
O: 1

6) Empirical formula:

C₄H₅N₂O₁

7) Calculate the approximate mass of the empirical formula:

4 × 12 + 5 × 1 + 2 × 14 + 1 × 16 = 97 g/mol

So, since that number is not between 150 and 200 g/mol, multiply by 2: 97 × 2 = 194, which is between 150 and 200.

Thus, the estimate is 194 g/mol

7 0

3 years ago

How important is the resonance structure shown here to the overall structure of carbon dioxide?

Tcecarenko [31]

1. Resonance structures are a better description of a Lewis dot structure .

2. Best resonance structure is the one with the least formal charge.

EXPLAINATION OF RASONANCE STRUCTURE OF CARBON DIOXIDE

1.Carbon dioxide has three resonance structures .

2. The CO2 molecule has a total of 16 valence electrons ,

1C = 4 electrons

2O= 12 electrons

three resonance structures for CO2

1. The atoms in all three resonance structures have full octets;

structure 1 will be more stable because it has no separation of charge.

2. Structures 2 and 3 show charge separation caused by the presence of formal charges on both oxygen atoms.

6 0

3 years ago

How much mass (in grams) is in a 3.25 mol sample of NH4OH?

Sergeeva-Olga [200]

Answer:

114 grams

Explanation:

1. NH4OH molecular weight: The molar mass of NH4OH = 35.0458 g/mol...

2. Convert grams-NH4OH-to-moles or moles-NH4OH-to-grams. Molecular weight calculation: 14.0067 + 1.00794*4 + 15.9994 + 1.00794.

3 0

3 years ago