The question is confusing and all the answers are not there but it is B C and D
Answer:
1. 35 mg of H₃PO₄
2. 27 mol AlF₃; 82 mol F⁻
3. 300 mL of stock solution.
Explanation:
1. Preparing a solution of known molar concentration
Data:
V = 80 mL
c = 4.5 × 10⁻³ mol·L⁻¹
Calculations:
(a) Moles of H₃PO₄
Molar concentration = moles of solute/litres of solution
c = n/V
n = Vc = 0.080L × (4.5 × 10⁻³ mol/1 L) = 3.60 × 10⁻⁴ mol
(b) Mass of H₃PO₄
moles = mass/molar mass
n = m/MM
m = n × MM = 3.60 × 10⁻⁴ mol × (98 g/1 mol) = 0.035 g = 35 mg
(c) Procedure
Dissolve 35 mg of solid H₃PO₄ in enough water to make 80 mL of solution,
2. Moles of solute.
Data:
V = 4900 mL
c = 5.6 mol·L⁻¹
Calculations:
Moles of AlF₃ = cV = 4.9 L AlF₃ × (5.6 mol AlF₃/1L AlF₃) = 27 mol AlF₃
Moles of F⁻ = 27 mol AlF₃ × (3 mol F⁻/1 mol AlF₃) = 82 mol F⁻.
3. Dilution calculation
Data:
V₁= 750 mL; c₁ = 0.80 mol·L⁻¹
V₂ = ? ; c₂ = 2.0 mol·L⁻¹
Calculation:
V₁c₁ = V₂c₂
V₂ = V₁ × c₁/c₂ = 750 mL × (0.80/2.0) = 300 mL
Procedure:
Measure out 300 mL of stock solution. Then add 500 mL of water.
statement about enzymes that is correct is
b. they are large molecules that increase the rate of biologically important reactions
Enzymes are proteins that catalyse, in other words increase the rate of the biological reactions.
Biological functions that are vital for the bodies to survive, have large activation energy barriers. For this reason enzymes are used that reduce the activation energy required for the reaction to initiate. this enables the reactions to proceed.
Substrates bind to the enzyme, reaction occurs and substrate converts to products, that are released from the enzyme, leaving the enzyme unchanged.
so the correct answer is B.
Answer:
C
Explanation:
Rust is a chemical change (reaction) all of the other options only change the state meaning that it is a physical reaction.
Answer:
The reducing agent donates electron to the oxidizing agent and gets oxidized itself
Explanation:
In an oxidation-reduction reaction, also known as REDOX reaction, one of the reactants is called OXIDIZING AGENT while the other is called REDUCING AGENT. The reducing agent is called so because it reduces another substance in the reaction.
It reduces another atom/ion by donating electrons to that atom, hence, getting oxidized itself in the process. For example, in the following reaction:
H2 + F2 → 2HF
Fluorine is getting oxidized from -2 to 0 by donating electrons to H and reducing it from +2 to 0.
