Heat can be absorbed or produced
Answer:
a) 
is the mass of 1 mole of bricks.
b) 
moles of bricks have a mass equal to the mass of the Earth.
Explanation:
a) Mass of brick = 4.0 kg
1 mole = 
particles/ atoms/molecules
Mass of 
bricks :
is the mass of 1 mole of bricks.
b)
Mass of the Earth = M = 
Mass of 1 mole of brick = m=
Let the moles of brick with equal mass of the Earth be x.
moles of bricks have a mass equal to the mass of the Earth.
Answer:
2.86g
Explanation:
Mass of HCl = 2.87g
Mass of water = 3.75g
Mass of NaCl = 1.98g
Unknown:
Mass of NaOH reacted = ?
Solution:
The reaction expression is given as:
HCl + NaOH → NaCl + H₂O
According to the law of conservation of mass, the mass of reactants and products must be the same.
Mass of HCl + Mass of NaOH = Mass of NaCl + Mass of H₂O
2.87g + Mass of NaOH = 1.98g + 3.75g
Mass of NaOH = 1.98g + 3.75g - 2.87g = 2.86g
Answer:
valency of an element is a combining power of an element.
for example oxygen has six valance electron but its valency is 2.
hope it helps.
