Find the molality of the solution if 2.5 moles of CaBr2 are dissolved in 5 kg of water.
2 m
500 m
5 x 10-4 m
0.5 m
The molality of the solution is calculated using the formula:
molality = moles of solute ÷ mass of solvent in kg
In this case, the moles of CaBr2 is given as 2.5 moles and the mass of the solvent (water) is given as 5 kg.
molality = 2.5 moles ÷ 5 kg = 0.5 m
Therefore, the molality of the solution is 0.5 m.
What is the mass of 8 atoms of copper in grams?
63.5 g
7.58 x 1022 g
1.33 x 10-23 g
8.44 x 10-22 g
To calculate the mass of 8 atoms of copper, we need to know the atomic mass of copper (Cu). According to the periodic table, the atomic mass of copper is 63.55 g/mol.
The molar mass of copper is the mass of one mole of copper, which is 63.55 g/mol. Therefore, the mass of one copper atom is:
63.55 g/mol ÷ 6.022 x 10²³ atoms/mol = 1.055 x 10^-22 g/atom
To find the mass of 8 copper atoms, we can multiply the mass of one copper atom by 8:
8 atoms x 1.055 x 10^-22 g/atom = 8.44 x 10^-22 g
Therefore, the mass of 8 atoms of copper is 8.44 x 10^-22 g (option D).
In the equation NaHCO3 + HCl → NaCl + H2CO3, what is the conjugate acid?
NaHCO3
HCl
H2CO3
NaCl
In the given chemical equation,
NaHCO3 + HCl → NaCl + H2CO3
The conjugate acid of a base is the species that is formed when the base accepts a proton (H+). Here, NaHCO3 can act as a base and can accept a proton (H+).
NaHCO3 + H+ → Na+ + H2CO3
In this equation, NaHCO3 accepts a proton (H+) and forms its conjugate acid H2CO3. Therefore, H2CO3 is the conjugate acid in the given equation (option C).
0.
Is the following reaction endothermic or exothermic?
H2 + Br2 --> 2 HBr
H= +72.8 kJ
endothermic
exothermic
In the given reaction:
H2 + Br2 → 2 HBr
It is given that H = +72.8 kJ. This represents the enthalpy (heat) change of the reaction.
If the value of H is positive, that means the reaction absorbed heat from the surroundings, and the reaction is endothermic.
If the value of H is negative, that means the reaction released heat to the surroundings, and the reaction is exothermic.
In this case, the value of H is positive (+72.8 kJ), indicating that heat is absorbed during the reaction. Therefore, the given reaction is endothermic.
What is the molarity of a solution that contains 125 g NaCl in 4.00 L solution? (molar mass of NaCl = 58.44 g/mol)
31.3 M
2.14 M
0.535 M
8.56 M
Molarity is defined as the number of moles of solute per liter of solution.
The first step is to calculate the number of moles of NaCl present in the solution:
Number of moles of NaCl = mass ÷ molar mass
Number of moles of NaCl = 125 g ÷ 58.44 g/mol
Number of moles of NaCl = 2.14 mol
Next, we can use the formula for molarity:
Molarity = number of moles of solute ÷ volume of solution (in liters)
Molarity = 2.14 mol ÷ 4.00 L = 0.535 M
Therefore, the molarity of the solution is 0.535 M (option C).
A new planet is discovered. What elements do you expect it to be composed of?
new elements that haven’t yet been discovered
the same elements Earth and other planets are made up of
only hydrogen and helium
there is not enough information to tell