How much water must be added to 1 liter of a 5% saline to get a 2% saline solution

the amount of saline must be the same before and after mixing:

.05(1) + 0(x) = .02(1+x)
.02x = .03
x = 1.5

check:
5% of 1L = .05L saline
2% of 2.5L = .05L saline

or, you can say that since you want 2/5 the concentration, you need 5/2 the original volume, or 2.5L

To find out how much water must be added to a 1 liter of 5% saline to get a 2% saline solution, we can set up a proportion.

Let's first determine the amount of saline in the original 1 liter of 5% saline solution:

Saline in 1 liter of 5% saline = 1 liter * 5% = 0.05 liters.

To get a 2% saline solution, the saline content should be equal to 2% of the total volume of the solution. Let's assume the amount of water to be added is 'x' liters.

Saline in x liters of water = x liters * 2% = 0.02 liters.

Setting up the proportion:

0.05 liters / 1 liter = 0.02 liters / (1 liter + x liters).

Cross-multiplying:

0.05 liters * (1 liter + x liters) = 0.02 liters * 1 liter.

0.05 liters + 0.05x liters = 0.02 liters.

0.05x liters = 0.02 liters - 0.05 liters.

0.05x liters = 0.03 liters.

Dividing both sides by 0.05, we get:

x liters = 0.03 liters / 0.05.

x liters = 0.6 liters.

Therefore, 0.6 liters of water must be added to 1 liter of a 5% saline solution to obtain a 2% saline solution.

To determine the amount of water needed to dilute a 5% saline solution to a 2% saline solution, we'll need to use a formula based on the principle of mixtures:

C₁V₁ + C₂V₂ = C₃V₃

Where:
C₁ = concentration of the initial solution (5%)
V₁ = volume of the initial solution (1 liter)
C₂ = concentration of the water (0% saline concentration)
V₂ = volume of the water to be added (unknown)
C₃ = concentration of the final solution (2%)
V₃ = volume of the final solution (1 liter + V₂)

First, let's plug in the given values into the formula:

(5%)(1 liter) + (0%)(V₂) = (2%)(1 liter + V₂)

Now, let's simplify and solve for V₂:

0.05 liter + 0 = 0.02 liter + (0.02 liter)(V₂)
0 = 0.02 liter + (0.02 liter)(V₂) - 0.05 liter
0 = (0.02 liter)(V₂) - 0.03 liter

To isolate V₂, let's subtract 0.02 liter from both sides:

-0.02 liter = (0.02 liter)(V₂) - 0.03 liter - 0.02 liter
-0.02 liter = (0.02 liter)(V₂) - 0.05 liter

Now, we can divide both sides by 0.02 liter:

(-0.02 liter) / (0.02 liter) = (0.02 liter)(V₂) / (0.02 liter)

-1 = V₂

Therefore, you would need to add -1 liter of water to the 1 liter of 5% saline solution to obtain a 2% saline solution.

However, a negative volume doesn't make sense in this context. In practical terms, it means that you cannot dilute a 5% saline solution with water to achieve a 2% saline solution. To achieve a 2% saline solution, you would need to start with a lower concentration of saline or use alternative methods.