Answer:
(A) N4H6 (B) H2O (C) LiH (D) C12H26
Explanation:
The given compounds have been arranged from left to right in order of increasing percentage by mass of hydrogen.
The percent by mass of hydrogen can be calculated by mass of hydrogen in that compound divided by total mass of that compound and finally multiplying the result with 100 to obtain the required percentage.
Answer:
a) The relationship at equivalence is that 1 mole of phosphoric acid will need three moles of sodium hydroxide.
b) 0.0035 mole
c) 0.166 M
Explanation:
Phosphoric acid is tripotic because it has 3 acidic hydrogen atom surrounding it.
The equation of the reaction is expressed as:
1 mole 3 mole
The relationship at equivalence is that 1 mole of phosphoric acid will need three moles of sodium hydroxide.
b) if 10.00 mL of a phosphoric acid solution required the addition of 17.50 mL of a 0.200 M NaOH(aq) to reach the endpoint; Then the molarity of the solution is calculated as follows
10 ml 17.50 ml
(x) M 0.200 M
Molarity = 
= 0.0035 mole
c) What was the molar concentration of phosphoric acid in the original stock solution?
By stoichiometry, converting moles of NaOH to H₃PO₄; we have
= 
= 0.00166 mole of H₃PO₄
Using the molarity equation to determine the molar concentration of phosphoric acid in the original stock solution; we have:
Molar Concentration = 
Molar Concentration = 
Molar Concentration = 0.166 M
∴ the molar concentration of phosphoric acid in the original stock solution = 0.166 M
The mass of reacted magnesium chloride is 23.75g, percent by mass of solution magnesium chloride is 90.9%.
<h3>What is the relation between mass & moles?</h3>
Relation between the mass and moles of any substance will be represented as:
n = W/M, where
- W = given mass
- M = molar mass
Moles of MgCl₂ = 200g / 95g/mol = 2.1mol
Moles of NaOH = 20g / 0.5mol
Given chemical reaction is:
MgCl₂ + 2NaOH → 2NaCl + Mg(OH)₂
From the stoichiometry of the reaction it is clear that
- 1 mole of MgCl₂ = reacts with 2 moles of NaOH
- 0.5 mole of NaOH = reacts with (1/2)(0.5)=0.25 moles of MgCl₂
Mass of reacted MgCl₂ = (0.25mol)(95g/mol) = 23.75g
Percent by mass of MgCl₂ in the given solution mixture will be calculated as:
- % by mass = (Mass of MgCl₂ / Total mass of mixture) × 100%
- Percent by mass of MgCl₂ = (200/200+20)×100% = 90.0&
In the above reaction we obtain NaCl as a solid, and MgCl₂ is the limiting reagent in it, from which 2 moles of NaCl is produced means
- 0.25 moles of MgCl₂ = produces 0.5 moles of NaCl
Mass of NaCl = (0.5mol)(58.5g/mol) = 29.25g
Hence, mass of reacted MgCl₂ is 23.75g, percent by mass of solution magnesium chloride is 90.9% and mass of the obtained solid is 29.25g.
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Answer:
The system gains 126100 J
Explanation:
The heat can be calculated by the equation:
Q = nxCxΔT, where Q is the heat, C is the heat capacity,n is the number of moles and ΔT is the variation of temperature (final - initial). The number of moles is the mass divided by the molar mass, so:
n = 250/4 = 62.5 mol.
The system must be in thermal equilibrium with the surroundings, so if the temperature of the surroundings decreased 97 K, the temperature of the system increased by 97 K, so ΔT = 97 K
Q = 62.5x20.8x97
Q = 126100 J
