Answer:
ΔS > 0 only for choice E: CH4(g) + H2O (g) → CO(g) + 3 H2(g)
Explanation:
Our strategy in this question is to use the trend in entropies :
S (solids) less than S (liquids) less than S (gases)
Also we have to look for the molar quanties involved of each state and their change to answer the question:
A. N2(g) + 3 H2(g) → 2 NH3(g)
Here we have 4 moles gases going to 2 moles of products, so the change in entropy is negative.
B. Na2CO3(s) + H2O(g) + CO2(g) → 2 NaHCO3(s)
The change in entropy is negative since we have 2 mol gases in the reactants and zero in the products.
C. CH3OH(l) → CH3OH(s)
A liquid has a higher entropy than a solid so ΔS is negative
D. False see A,B,C
E. The change in moles of gases is 4 - 2= 2, therefore ΔS is greater than O.
Answer: completely (100%) dissociates, producing a significant amount of H+ and OH- ions in solution, making it conduct electricity well.
Explanation:
A strong acid is one that ionizes or dissociate completely in water to yield its hydrogen ion (H+) as the only positively charged ion.
For example: Hydrochloric acid (HCl) dissociates completely in water to give hydrogen ion and chlorine ion
HCl(aq) --> H+(aq) + Cl-(aq)
A strong base, on the other hand, dissociates completely in water to yield an hydroxyl ion (OH-) as the only negatively charged ion. A good example is Sodium hydroxide NaOH
NaOH (aq) --> Na+(aq) + OH-(aq)
And since mobile and charged ions help transmit electric current, a strong acid or base produces significant amount of H+ and OH- ions that conduct electricity well.
1. to calculate molar mass , you need average atomic mass of each element.
formula is simple
suppose we have Na2CO3
here it says
there are
2 atoms of Na
1 atom of C
3 atom of O
now
molar mass = (total atoms of Na × average atomic mass of Na) + ( total atom of C × average atomic mass of C )+ (total atom of O × average atomic mass of O)
i hope you can figure out it now.
in case of (NH4)2
this means you have 2 count of NH4
so total atoms of N = 2
total atoms of H = 4×2 = 8
so on you can now figure it out
2. balanced equation
here LHS and RHS shoild have same number of atoms of each element .
for example
H2 + Cl2 => 2HCl
here 2 atoms of H combined with 2 atoms of Cl , we know H and Cl combined and formed HCl now because total H atoms are 2 and Cl atoms are 2 in LHS then we should also have 2 atoms of each in right side
so thats why we have 2HCl in right side.
Try to figure out . let me know if need any help
Answer:
Exothermic reaction for the HCl, endothermic reaction for the water
Explanation:
Heat was lost by HCl as its temperature lowered, so it was an exothermic reaction for the HCL.
Heat was gained by water as its temperature increased, so it was an endothermic reaction for the water.
m = Mass of water = 100 g
c = Specific heat of water = 
= Change in temperature of water = 
Heat is given by
Heat gained by water is .
corrected question:
Determining Density and Using Density to Determine Volume or Mass
(a) Calculate the density of mercury if 1.00 × 10 g occupies a volume of 7.36 cm³
(b) Calculate the volume of 65.0 g of liquid methanol (wood alcohol) if its density is 0.791 g/mL.
(c) What is the mass in grams of a cube of gold (density = 19.32 g/cm) if the length of the cube is 2.00 cm?
(d) Calculate the density of a 374.5-g sample of copper if it has a volume of 41.8 cm³ A student needs 15.0 g of ethanol for an experiment. If the density of ethanol is 0.789 g/mL, how many milliliters of ethanol are needed? What is the mass, in grams, of 25.0 mL of mercury (density = 13.6 g/mL)?
Answer:
density = 
ρ=m/v ,m=ρv, v=m/ρ
(a)m=1*10g , v=7.36cm³
ρ=10/7.36 =1.36g/cm³
(b) m=65g, ρ=0.791 g/mL.
v= 65/0.791 =82.17g/mL
(c) ρ=19.32g/cm³, l=2cm, v=l³=8cm³
m=19..32*8=154.56g/cm³
(d) mass of copper=374.5g , v=41.8cm³
ρ=374.5/41.8 =8.96g/cm³
mass of ethanol=15g, density of ethanol=0.789g/mL
v=15/0.789 =19.01mL
volume of mecury=25mL, density of mercury=13.6g/mL
m=25*13.6=340g
