Answer:
B) it is endothermic and the temperature decreased
Explanation:
Chemical reactions can be classified as endothermic and exothermic.
Endothermic reactions proceed with the absorption of heat energy (q) and have a positive value for q.
In contrast, Exothermic reactions proceed with the liberation of heat energy (q) and have a negative value for q.
It is given that the value of q = +450 J. Since q is positive, this implies that heat energy is absorbed from the surroundings resulting in a fall in temperature. Hence the reaction is endothermic.
2250cm3= 2250/1000000m3=.00225m3
<span>The right answer is the option B. Close to 99 percent. The atmosphere is a mixture of gases: nitrogen, oxygen, CO2, H2O, argon, among others. Nitrogen is about 78% and oxygen is about 21%, so they two together constitute about 99 percent of the Earth's atmosphere.</span>
it would be heating of 32g of s and 56g of Fe to produce 88g of FeS and unused reactants
Answer:
32 mL
Explanation:
<em>A chemist must prepare 500.0mL of hydrobromic acid solution with a pH of 0.50 at 25°C. He will do this in three steps: Fill a 500.0mL volumetric flask about halfway with distilled water. Measure out a small volume of concentrated (5.0M) stock hydrobromic acid solution and add it to the flask. Fill the flask to the mark with distilled water. Calculate the volume of concentrated hydrobromic acid that the chemist must measure out in the second step. Round your answer to 2 significant digits.</em>
<em />
Step 1: Calculate [H⁺] of the dilute solution
pH = -log [H⁺]
[H⁺] = antilog -pH = antilog -0.50 = 0.32 M
Step 2: Calculate [HBr] of the dilute solution
HBr is a strong acid that dissociates according to the following equation.
HBr ⇒ H⁺ + Br⁻
The molar ratio of HBr to H⁺ is 1:1. The concentration of HBr is 1/1 × 0.32 M = 0.32 M.
Step 3: Calculate the volume of the concentrated HBr solution
We will use the dilution rule.
C₁ × V₁ = C₂ × V₂
V₁ = C₂ × V₂ / C₁
V₁ = 0.32 M × 500.0 mL / 5.0 M
V₁ = 32 mL
