I am filing out a study guide and needed coaching on some question. thank you

0.765 g of He is placed in a balloon at 1.15 atm. The balloon expands to volume of 5.00 L. What is the temperature of the balloon?

a,3.45 K
b,91.6 K
c,93.4 K
d,366 K

At STP a sample of methane gas occupies a volume of 1250 mL. What is the volume of the methane at 100.°C and 760. torr?

a.1710 mL
b.1250 mL
c.915 mL
d.1420 mL

A solution is prepared by adding 25.0 g of methanol to water to make a total volume of solution of 95.4 mL. What is the weight/volume percent of this solution?

a.26.2%
b.3.81%
c.20.8%
d.25.0%

7.76 g of KBr was dissolved in water. The solution was diluted to a volume of exactly 250 mL. What is the molarity of the solution?

32.2 M

a.0.476 M
b.0.0652 M
c.0.0310 M
d.0.261 M

How many grams of Na2SO4 are present in 500. mL of a 0.750 M aqueous solution?

a.70.9 g
b.53.3 g
c.0.284 g
d.106 g
e.2.63 g

A serum concentration of Mg2+ of 1.75 mmol/L is equivalent to:

a.3.50 mEq/L
b.1.75 mEq/L
c.17.5 mEq/L
d.0.875 mEq/L

anyone know how to work out these problems?

i cant believe these arent answered yet. im sorry.

1. 366K
2. 1710 mL
3. 26.2
thats what i have so far

To answer this question, we can use the ideal gas law equation, which is stated as follows:

PV = nRT

Where:
P is the pressure (in atm)
V is the volume (in liters)
n is the number of moles of gas
R is the ideal gas constant (0.0821 L·atm/(mol·K))
T is the temperature (in Kelvin)

In this case, we have the following information:
Pressure (P) = 1.15 atm
Volume (V) = 5.00 L
Amount of gas (n) = We are not given the number of moles, but we can calculate it using the molar mass of helium (4.00 g/mol).
R is a constant and we already have its value.
Temperature (T) = unknown

To find the temperature, we need to rearrange the ideal gas law equation to solve for T:

T = PV / (nR)

First, we calculate the number of moles of helium in the balloon using the given mass.

Mass of helium (m) = 0.765 g
Molar mass of helium (M) = 4.00 g/mol

n = m / M
= 0.765 g / 4.00 g/mol

Next, substitute the values into the equation:

T = (1.15 atm) * (5.00 L) / ((0.765 g / 4.00 g/mol) * (0.0821 L·atm/(mol·K)))

T = (1.15 * 5.00 * 4.00 * 0.0821) / 0.765

Calculating this yields a value of around 91.6 K.

Therefore, the answer is option b, 91.6 K.