Answer:
Nervous system directs your body to swear to release heat.
Explanation:
Sweat maintains homeostasis when overheating.
Sucrose, a sweet, white crystalline substance, C12 H22 O11, OBTAINED CHIEFLY FROM THE JUICE OF THE SUGAR CANE AND SUGAR BEET, BUT ALSO PRESENT IN SORGHUM, THE sugar maple, some palms, and various other plants, and having extensive nutritional, pharmaceutical, and industrial uses; any of the class of carbohydrates to which this substance belongs, as glucose, levulose, and lactose.
Answer:
- g) 0.20 mol
- h) 2.0 mol/dm³
- i) 2.8 g
Explanation:
<h2>a) </h2>
1. Data:
2. Solution:
i) Formulae:
- number of moles = mass in grams/Ar
- number of atoms = number of moles × Avogadro constant
- Avogadro constant = 6.022 × 10²³ atoms/mol
ii) Calculations:
- number of moles = 71g / 35.5(g/mol) = 2 mol
- number of atoms = 2mol × 6.022 × 10²³ atoms/mol = 1.20 × 10²⁴ atoms
<h2>b) </h2>
1. Data:
- 0.2 mol KOH
- Ar: H = 1, O = 16, k = 39
2. Solution
i)Formula:
- mass = number of moles × molar mass
ii) Molar mass:
- 1×1g/mol + 1×39g/mol + 1×16g/mol = 56g/mol
iii) Calculations:
- mass = 0.2 mol × 56g/mol = 11.2 g/mol ≈ 10g/mol (rounded to 1 significant figure)
<h2>c) </h2>
1. Data:
2. Solution
i) Formula:
- number of moles = mass in grams / Ar
ii) Calculations:
- number of moles = 1.4g / 7 gmol = 0.7 mol
<h2>d) </h2>
1. Data:
2. Solution
i) Formula:
- mass = number of moles × molar mass
ii) Calculations:
- molar mass = 8 × 32g/mol = 256 g/mol
- mass = 4 mol × 256 g/mol = 1,024 g ≈ 1,000 g (rounded to 1 significant figure)
<h2>e)</h2>
1. Data:
- Mr: Ca(NO₃)₂ . 2H₂O = 200
2. Solution
i) Formulae:
- number of moles = mass in grams / molar mass
ii) Calculations:
- number of moles = 50 g / 200 g/mol = 0.25 mol of Ca(NO₃)₂ . 2H₂O
The number of moles of water molecules is 2 times the number of moles of Ca(NO₃)₂ . 2H₂O.
- number of moles of water molecules = 2 × 0.25 mol = 0.5 mol
<h2>f) </h2>
1. Data:
2. Solution:
i) Formulae:
- number of atoms = number of moles × Avogadro constant
- number of moles = mass in grams / molar mass
ii) Calculations
- number of moles = 4.9g / 98g/mol = 0.050 mol
- number of atoms = 0.050 mol × 6.022 × 10²³ atoms/mol = 3.0×10²² atoms
<h2>g) </h2>
1. Data:
- V = 24 dm³ (air)
- 20% oxygen
- r.t.p ⇒ T = 298K, p = 1 atm
2. Solution
i) Formula:
ii) Calculation:
- R = 0.08206 (atm.dm³/K.mol)
- n = [ 1 atm × 24 dm³] / (0.08206atm.dm³/K.mol × 298K) = 0.98mol of air
- moles of oxygen = 20% × 0.98 mol ≈ 0.20 mol
<h2>h) </h2>
1. Data:
2. Solution
i) Formula:
- Molarity = moles of solute / volume of solution in dm³
ii) Calculations:
25cm³ × (0.1cm/dm)³ = 0.125 dm³
- Molarity = 0.25 mol / 0.125 dm³ = 2.0 mol/dm³
<h2>i) </h2>
1. Data:
- V = 35cm³
- M = 2 mol/dm³
- Mr NaOH = 40
2. Solution
i) Formulae:
- number of moles = M × V (in dm³)
- mass = number of moles × mola rmass
ii) Calculations:
- V = 35cm³ × (0.1dm/cm)³ = 0.035dm³
- number of moles = 2 mol/dm³ × 0.035 dm³ = 0.070 mol
- mass = 0.070 mol × 40 g/mol = 2.8 g
Answer:
C = 0.08M
Explanation:
molar mass of AlCl3
Al =27
Cl = 35.5
27+3(35.5) =133.5g/mol
n= mass/Molar mass
n =CV
CV = mass/molar mass
C x 500 x 10^-³ = 5/133.5
C x 500 x 10^-³ = 0.04
C = 0.04/500 x 10^-³
C = 0.08M
