Answer:
17.3 g Cr
Explanation:
To find the mass of chromium, you need to (1) convert moles Si to moles Cr (using the mole-to-mole ratio from equation coefficients) and then (2) convert moles Cr to grams Cr (using the atomic mass). It is important to arrange the conversions in a way that allows for the cancellation of units. The final answer should have 3 sig figs to match the sig figs of the given value (0.250).
3 Si + 2 Cr₂O₃ ---> 4 Cr + 3 SiO₂
^ ^
Atomic Mass (Cr): 51.996 g/mol
0.250 moles Si 4 moles Cr 51.996 g
------------------------- x -------------------- x ------------------- = 17.3 g Cr
3 moles Si 1 mole
The correct answer is 1.1 moles
Answer:
0.497 moles/L
Explanation:
The reaction that takes place is:
- C₃H₆O₃ + NaOH → C₃H₅ONa + H₂O
First we c<u>alculate the moles of lactic acid in 0,821 g</u>, using its molar mass:
- 0,821 g ÷ 90 g/mol = 9,122x10⁻³mol lactic acid
<em>One mole of lactic acid reacts with one mole of sodium hydroxide</em> (it is a monoprotic acid), so in 18,34 mL of NaOH solution there are 9,122x10⁻³moles of NaOH:
- 18.34 mL ÷ 1000 = 0,01834 L
- 9,122x10⁻³mol ÷ 0,01834 L = 0.497 moles/L
Explanation:
Gravitational potential energy
= mgh
= (5kg)(9.81N/kg)(150m)
= 7357.5J.
